Finometer User`s Guide

Transcription

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Finometer TM User’s Guide
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FMS, Finapres Medical Systems BV
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C 2002 FMS
Version 1.10, dd: 2002.05.06
This document is for information purposes only.
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C 2002 FMS
Customer support
The Finometer is manufactured by FMS, Finapres Medical Systems BV, at the location given below.
The Finometer and its accessories are constructed of high quality materials and great care has been taken in
its manufacture. We stand behind our product and will do what is in our power to have you as a satisfied
customer and Finometer user.
If the product fails to function properly, or when assistance, or service, or recalibration is needed, please
contact:
Simon Stevinweg 48
NL-6827 BT ARNHEM, The Netherlands
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phone
fax
email
web
:
:
:
:
+31 26 3849080
+31 26 3849081
[email protected]
www.Finapres.com
If accessories for Finometer are needed, such as extra cuffs, or further copies of this User Guide, please contact:
Mr R Roelandt
Decavee 12,
B-1790 AFFLIGEM, Belgium
phone
fax
email
+32 53 685626
+32 53 685636
[email protected]
Finometer contains no field serviceable parts. Servicing of any component of this device, therefore, is
to be performed by FMS only. Unauthorized repairs or modifications may violate the conformity of Finometer
with the requirements in the Medical Device Directive 93/42/EEC set forth by FMS.
Warranty
The Finometer system is guaranteed by FMS, Finapres Medical Systems BV for a period of one year after the
date of purchase. During this warranty period FMS will, without charge for labor or parts, repair or replace
defective parts.
The warranty does not include the following:
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Finger cuffs. Finger cuffs, however, are reusable items which can, given proper care and handling, often
be used for several years.
Transport costs and insurance of the shipment of the Finometer to FMS.
Defects caused by repairs through unauthorized personnel, or the use of accessories not obtained from, or
approved by FMS.
Periodic check--ups, upon request of the user.
Damage through misapplication, misuse, or failure to follow the instruction in this User’s Guide, or in
other accompanying documents.
Accidents that affected Finometer or its accessories.
Disclaimer
DISCLAIMER OF WARRANTIES AND LIMITATIONS
fms makes no warranty or representation, either express or implied, with respect to the
finometer device, its quality, merchantability, or fitness for a particular purpose. the
equipment is provided as is, no oral or written information or advice given by either party
or its employees shall create a warranty or make any modification, extension or addition
to the warranty.
fms shall not be liable for any direct, indirect, incidental or consequential damages, including lost profits and damages for personal injury or property damage, arising from or
in connection with the licensed rights or its use whatsoever.
in no case shall fms, finapres medical systems bv’s liability exceed the purchase price for
the device.
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Information in this document is subject to change without notice and does not represent a commitment on
the part of FMS, Finapres Medical Systems BV.
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The BeatScope software is furnished under a license agreement. The software may be used only in accordance
with that agreement. Beatscope includes the Finometer--to--PC link program: Finolink, which can also be
used as a stand--alone program, and can be copied to any Windows PC and run. Finolink downloads data
packets, unpacks these files, and allows limited remote control of Finometer.
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BeatScope, Finolink, Finometer, Modelflow, and Portapres are trademarks of FMS, Finapres Medical Systems
BV. Finapres is a trademark of Ohmeda Monitoring Systems.
No part of this publication may be reproduced, transmitted, transcribed, stored in a retrieval system, or
translated into any language in any form by any means, for any purpose other than the purchaser’s personal
use only after prior written permission of FMS, Finapres Medical Systems BV
Dear Finometer user
This guide has been written to ease you into doing
measurements with Finometer. With its Start display
and three built--in instruments it might appear that
you are in for a steep learning curve. We hope that
you will find this as untrue as it was for the young
person on the facing page.
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The Start display (page 44) appears when Finometer electrical power is turned on. It is the super
device since it allows the starting of each of the three
instruments of Finometer. As further options, you
may output one of two analog calibration waveforms
or view a series of instruction or help slides on how
to wrap cuffs, apply the finger hydrostatic height correction sensors, and more. Start any instrument or
action by pressing the corresponding button twice.
Finometer--research (page 49) is a finger arterial
pressure measurement instrument with configurability and many options. It was designed principally
as a noninvasive hemodynamics monitor for research,
displaying arterial pressure, rate and flow. It has
the remote control functions: start/stop a measurement, start/stop Physiocal, and start/stop a return-to--flow calibration. It will also store externally supplied markers. It has three external analog signal inputs and may even be run from an external pressure
wave without starting finger pressure.
a limited number of function keys. It was designed
principally for clinical monitoring of finger pressure.
It has no remote control option and does not sample
and store external analog signals. It does, however,
produce the same file as does Finometer--research,
and off--line evaluation of the data is not in any way
limited.
Finometer--classico (page 91) is an upper arm
cuff inflate/deflate controller and Korotkoff phase
marking instrument. Inflation and deflation rates
are setable. Together with a stethoscope it facilitates auscultatory blood pressure measurements and
with the mark facility for the Korotkoff phases a full
record of each measurement is output.
Exiting an instrument is by pressing simultaneously the two front panel buttons marked // and
.. , which returns you to the Start display.
Suggested reading is to first turn to chapter 1
with warnings and cautions. Next, try out the quick
start guide of chapter 2 which describes in order every step to perform a finger blood pressure measurement for the first time. Soon thereafter, wrapping a
finger cuff and entering patient data will quickly become routine, and starting a measurement is a one
button operation.
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Finometer--clinique (page 81) is a finger arterial
pressure measurement instrument with a fixed display of pressure and heart rate, and operation is via
If you find anything missing in this User’s Guide—it
is in its first version—please contact us as we may be
able to provide the missing information.
Dear Interactive Guide user
The Interactive Finometer User’s Guide has been designed to easily find a topic of interest and to follow
its information trail.
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Interactive User’s Guide screen layout. The
page layout consists of two parts: At the left there is a
colored control column with often a small figure at the
top and a set of browse buttons below. At the right
there is a text page with an occasional embedded figure or table or animated cartoon (section 4.2). In
a text page blue colored items are clickable to reach
an associated topic. In the table of contents everything is clickable. Return to where you came from by
clicking the go back button.
Figures. Click on the stamp sized figure upper left
to display it in full size. Click again and the text page
reappears. Or use the show figure and hide figure
buttons.
Paging.
Jump to a page by clicking the page
button and typing your page number. Further use
the previous page and next page buttons.
Searching. A word or a phrase is found by clicking the search text button and typing your word or
phrase. For its next occurrence click search again
. Acrobat cannot always find ligatures. Search for
‘Modelflow’ via ‘Model’.
Contents.
The table of contents presents an
overview of sections principally ordered according
to the various instruments or user (interfaces 3.4)
present in the Finometer device. Jump to it by clicking the contents button. The table of contents is
followed by a list of figures and a list of tables. There
is no button to jump to these lists directly.
Glossary. The glossary is one of the appendices and
explains terms used in connection with Finometer
and finger blood pressure measurement. The terms
are listed in the index under “Glossary”
Index.
At the end of this Guide you find an alphabetical index of words of phrases. To ease searching there are multiple entries with somewhat differing
terms so that you may find:
Analog I/O
calibration waveforms
Calibration
signals
square wave
pressure wave
Start display
calibration signals
all leading to the same page. Jump to the index by
clicking the index button.
Close document. Click close document to close
the Interactive User’s Guide but not the reader (Acrobat 4.0 or higher). To close the reader click the ×
at the upper right, or type <Alt><F4>.
Contents
Customer support
3
Dear Finometer user
6
Dear Interactive Guide user
7
1
Uses, warnings, cautions,
protective measures
1.1
When to use Finometer?
1.1.1
Noninvasive
1.1.2
Modelflow
1.2
When not to use Finometer
1.3
Avoiding injury to patient and
personnel
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15
16
16
16
17
18
2 To a quick start
2.1
Setting up Finometer
2.2
A first measurement
2.3
Accessing the packet file
2.4
Sampling external signals
2.5
External offset and sensitivity
2.6
Save & recall the configuration
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20
21
22
23
24
25
3 Introduction
3.1
What is Finometer?
3.2
Methodology
3.3
Features
3.4
User interfaces
3.5
Derived parameters—beat--to--beat
3.6
Bias and precision
3.6.1
Arterial pressure
3.6.2
Cardiac output
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28
29
30
31
32
32
32
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4 Help slides
4.1
Cuff selection & handling slide
4.2
Cuff and frontend mounting slide
4.3
Difficult situations
4.3.1
Cold fingers
4.3.2
Arm arterial sclerosis
4.3.3
Costo--clavicular cutoff
4.3.4
Cyanotic finger tips
4.4
Height sensor nulling &
placement slide
4.4.1
Nulling
4.4.2
Sensitivity
4.5
The Finometer front panel
buttons slide
4.6
Waveform modeling & level
correction slide
4.7
Level calibration by return--to-flow slide
4.8
Finometer instrument selection slide
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35
36
37
37
37
37
38
5 The Start display
5.1
The Finometer selftest
5.2
The calibration signals
5.3
Off--line downloading of stored
packet files
5.4
Failure to start—rebuilding the index
44
45
46
The Finometer--research
instrument
6.1
Entering patient data—research
6.2
Layout of the Research display
6.3
The error message display—research
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39
40
41
42
43
47
48
6
49
51
52
53
6.4
6.5
6.6
6.7
6.7.1
6.7.2
6.8
6.9
6.10
6.11
6.12
6.13
6.14
Files downloading and remote control
The Help card
The Describe subject card
Setting a subject’s data
Thermodilution cal
Aortic diameter cal
The pressure--volume diagrams
The Select trends card
Cardiac oxygen supply/demand
The Select A/D signal card
The Physiocal card
The Return--to--flow--cal card
The Derived variables card
54
55
56
57
57
57
58
59
60
61
62
63
64
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Configuring the Research
instrument
7.1
Transducer check—buffer pressure
7.2
Transducer check—height nulling
7.3
Transducer check—height calibration
7.4
Transducer check—finger cuff
7.5
Transducer check—arm cuff
7.6
Pressure reconstruction
7.7
External signal input
7.8
Which channel to choose?
7.9
Setting date and time
7.10 Miscellaneous—finger switching
7.11 Miscellaneous—display units selection
7.12 Miscellaneous—the beeper
7.13 Miscellaneous—saving a configuration
7.14 Miscellaneous—loading a configuration
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68
69
70
71
72
73
74
75
76
77
78
79
80
8 The Finometer--clinique instrument
8.1
Entering patient data—clinique
8.2
The error message display—clinique
8.3
Files downloading from a remote PC
81
82
83
84
8.4
8.5
Show trends
The control buttons during off-line idling
Layout of the Clinique display
The control buttons during a
measurement
Scale compression
Performing a return--to--flow
calibration
85
9 The Finometer--classico instrument
9.1
Setting the in-/deflate and
readout parameters
9.2
The Classico calibration waveform
9.3
The normal Riva-Rocci/Korotkoff measurement
9.4
The Classico random zero measurement
91
A Specifications
A.1 Unpacking—The Finometer
components
A.2 Patient safety measures
A.3 Protective measures
A.4 Analog Input/Output
A.5 Environmental specifications
A.6 Electrical specifications
A.7 Mechanical specifications
A.8 Instrumental information
A.9 Instrumental accuracy
A.10 Connecting external equipment
A.11 Remote control
A.12 Safe data storage—Data durability
A.13 Unpacking—The data packets
A.14 Cleaning
97
8.6
8.7
8.8
8.9
86
87
88
89
90
93
94
95
96
99
100
101
103
104
105
106
107
108
109
110
111
112
113
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B
Error messages
114
E
Literature references
126
C
Derived parameters
116
F
Index
128
D
Glossary
117
Colophon
138
Figures
1
1
2.1
2.2
2.3
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2.4
2.5
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2.7
3.1
A novice Finometer operator
studies the button--screen interaction.
The Interactive User’s Guide
screen layout and buttons. The
buttons and blue colored clickable
items in the text (not present in
this figure) facilitate reaching the
nooks and crannies of this guide.
The frontend cable connector.
The analog input/output (I/O) box.
The front end (top) with rear
mounted telephone receptacle to
receive the height sensor electrical
connector and, separately, the
height sensing system (bottom).
The pillbox is the reference sensor
to be attached at heart level.
The Finolink option select (top)
and download (bottom) display.
Reading an external signal on
input--4 of the analog I/O box
(upper panel) and adjusting its
offset to zero (lower panel).
Adjusting (here) channel 1
sensitivity by bringing it down.
Saving a configuration under Blue.
The three user interfaces. The
upper two are finger pressure
devices, the bottom interface is to
the Riva--Rocci/ Korotkoff device.
3.2
6
4.1
7
19
20
4.2
4.3
4.4
4.5
4.6
21
4.7
22
4.8
23
24
25
4.9
5.1
30
Some parameters derived
from the current pressure and
simulated flow waveforms, timed
at the begin upstroke instant.
The start display: two inventions
founding Finometer.
Cuff size selection.
Cuff position on a finger.
Click on figure to start a movie
on finger cuff positioning.
Height correction system nulling
and sensor placement.
Finometer front panel layout and
description of the functions of the
buttons. The arm cuff is inflated
via the socket labeled i. Arm cuff
pressure is sensed via socket s
Transfer functions (left) and
effect of level correction (right).
Finger pressures, FAP, (left
panels) and reconstructed
brachial pressures, reBAP, (right
panels) compared to intrabrachial
artery pressures, BAP.
Program selection options. The
three softkey selectable Finometer
instruments.
The Finometer Start display with
the [Help slides] button highlighted.
31
34
35
36
36
39
40
41
42
43
44
5.2
5.3
5.4
6.1
6.2
6.3
6.4
6.5
6.6
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6.7
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6.8
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6.9
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6.10
Start display showing all
deviations from normal that can
be detected in the Finometer
hardware selftest.
The two analog calibration
signals available in Finometer.
Start display when Finometer has
been approached for off--line files
downloading by the Finolink program.
Finometer--research selected in
the Start display.
First or opening display after
starting Finometer--research.
The Finometer--research display layout.
An error message.
Finometer--research display with
off--line files downloading in progress.
The first help paragraph is always
displayed initially since it says
how to stop a measurement run.
The {Describe subject} card
shown before proper subject data
are entered and confirmed.
The subject data have been
modified but not confirmed.
The blue message instructs you
to press the [Describe subject]
button to confirm the changes.
The great effect of age on aortic
nonlinearity is shown in these two
highlighted diagrams.
The relationship between the
settings on the {Select trends}
card and both trend display panels.
6.11
6.12
45
46
47
6.13
49
6.14
51
52
53
6.15
54
7.1
55
56
7.2
7.3
57
7.4
58
7.5
59
A measure for cardiac time-tension is displayed in m Hg.
The Finometer internal finger
plethysmogram is shown on a
time scale of 0.5 s per division,
with zero in the middle, on a
±2.5 V full scale. A Physiocal
procedure is in progress.
The Physiocal side of the
{Physiocal & RTF--cal} card with
Physiocal turned off.
The RTF--cal side of the
{Physiocal & RTF--cal} card with
ramp inflate selected.
Twelve pressure and flow derived
variables presented as 8--beat
running averages updated every
1 second.
Opening display of the
{Configure} card, with sections,
subsections perhaps, and
instructions in blue.
Arm cuff air buffer pressure check.
The hydrostatic height sensing
system check display panel.
Height on the tab card is in cm.
In the left information display the
Hite: value is shown in mmHg.
The hydrostatic height sensing
system check display when the
sensors are held apart 50 cm vertically.
Checking the finger cuff pressure
transducer.
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61
62
63
64
65
67
68
69
70
7.6
7.7
7.8
7.9
7.10
7.11
7.12
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7.13
7.14
7.15
8.1
8.2
8.3
index
8.4
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8.5
Connecting piece (top) is a
Kuhnke socket (order nr 50.064),
6 × 1 mm air hose, and Luer
assembly, the screen display
(bottom) shows when performing
an arm cuff transducer test.
Changing from finger to brachial
pressure waveform reconstruction
to no reconstruction.
Selecting channel 1 for external input.
Setting a channel’s sensitivity.
Date and time on the {Configure}
card are related to Date: and
clock-TIME on screen.
Changing the finger switching interval.
Selecting the SI unit system and
hPa for pressure.
The system beeper turned off.
Saving a Finometer--research
configuration under Blue.
Loading a the Red Finometer-research configuration.
Finometer--clinique selected in
the Start display.
Entering patient data in
Finometer--clinique
Finometer--clinique displaying an
error message.
Off--line files downloading display
of Finometer--clinique. Patient
data was being entered when the
Finometer was approached by
Finolink for off--line downloading.
Display after pressing the [Show
trends] button.
8.6
8.7
71
8.8
72
73
74
8.9
75
76
77
78
79
8.10
9.1
9.2
9.3
80
9.4
81
82
83
84
85
9.5
A.1
D.1
D.2
D.3
D.4
D.5
D.6
Showing the yellow idling control
buttons.
Finometer--clinique display during
a measurement, showing its
layers. The display is off--colored
to emphasize the layers.
Showing the blue control buttons
during a measurement with the
Clinique instrument and the
waveform at high speed. Note the
begin upstroke markers.
Trend display just before (upper)
and after (lower) reaching the end
demonstrating scale compression.
Display after a return--to--flow
calibration took place.
Finometer--classico selected in the
Start display.
The Classico setup tab cards stacked.
The Classico calibration
waveform has 50 mmHg steps and
runs between 50 and 250 mmHg.
The Classico normal Riva--Rocci/
Korotkoff display.
The Classico random zero display.
The Finometer ready for a
measurement.
Some derived parameters.
A finger cuff.
The Modelflow model.
Nonlinear curves.
Square wave calibration.
Transfer functions.
86
87
88
89
90
91
93
94
95
96
99
118
119
121
121
124
125
Tables
3.1
3.2
3.3
6.1
7.1
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Differences (mmHg) between
FinAP and BAP.
Differences (mmHg) between
reBAP and BAP.
Differences (`/min) between
Modelflow and thermodilution C.O..
The Finometer internal analog signals.
C.1
32
32
33
61
74
Finometer derived parameters.
All parameters when displayed
are 8--beat averages. Indexed
parameters have a darker shade.
The clinique waveform display
shows beat--to--beat heart rate in
Yellow.
116
1 Uses, warnings, cautions, protective measures
This chapter lists a number of important precautions that we urge you to study before starting to measure a
patient for the first time. Listed are situations where, from extensive experience with Finapres and Finometer,
the device can be used and situations are listed when Finometer preferably should not be used. It tells you
about precision, which is limited, and about precautions you may take to optimize safety for the patient.
1.1
1.2
1.3
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When to use Finometer?
16
When not to use Finometer
17
Avoiding injury to patient and personnel
18
1.1 When to use Finometer?
Use Finometer when there is a need for a noninvasive
hemodynamic monitor providing an almost complete,
noninvasive characterization of the arterial circulation and its beat--to--beat variability in pressure and
flow, and in various parameters derived from these
continuous signals, such as systolic, diastolic and true
mean pressure, pulse interval, heart rate, and left ventricular ejection time, stroke volume, cardiac output,
systemic peripheral resistance, and a form of time-tension index.
1.1.1 Noninvasive
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The Finometer is a noninvasive instrument to measure blood pressure on the finger of a human. Since
it is noninvasive, application is associated with little risk. Noninvasive methods are usually associated with reduced accuracy. In Finometer, however,
the brachial artery pressure wave is reconstructed
in waveform and level. For this purpose patented
methods and algorithms are included, using an upper arm cuff return--to--flow systolic pressure determination, to substantially reduce inaccuracies. The
reconstruction procedures run fully automatically
as the default setting of Finometer, although they
can be de--selected. We have demonstrated in practice that accuracies of finger blood pressure after reconstruction are within the AAMI requirements of
±5 ± 8 mmHg against intrabrachial blood pressures
(for references see page 126). Application of Finometer in clinical practice seems not limited by inaccuracies or by risk to the patient.
1.1.2 Modelflow
In addition, Finometer includes the patented Modelflow method to derive continuous cardiac output
from finger pressure using a model. Compared to
carefully executed thermodilution cardiac output estimates the bias is near zero but precision is limited
(to 20%) until it has been calibrated with another
method. In tracking changes from control in percent
before, or in `/min cardiac output after calibration,
however, the Modelflow method (at 8% precision) is
as precise as or better than triple random thermodilution estimates.
1.2 When not to use Finometer
When 100% availability of arterial pressure is required in critically ill patients since treatment depends on it, and other means are available, Finometer
is not the preferred choice. Still, in two studies we
found that the overall percentage availability of Finapres in the operating room during coronary artery
bypass grafting 22 and of Portapres in 24 hour ambulatory recordings 11 was equal to that of the intraarterial lines. The finger is a distal measuring site and
page 17
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smooth muscle in the arteries and arterioles of the
circulation of hand and finger can come to full contraction. An extreme example of this is Raynaud’s
phenomenon. Measures have been built into Finometer to alert the user to such conditions developing.
When full contraction does occur finger pressure measurement is no longer possible, and cannot be restored
quickly.
1.3 Avoiding injury to patient and personnel
•
•
•
•
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•
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•
(US) Federal law restricts this device to sale by
or on the order of a physician. This device is
intended for use by trained health care professionals.
The physiological parameters provided by this
device have clinical significance only if determined by a physician and should not be used
as the sole means for determining a patient’s diagnosis.
Explosion hazard exists when operated in the
presence of flammable gases and liquids.
Protection against the ingress of liquids is limited. Do not apply electrical power to the device
when liquids did enter as this may cause internal
short circuits and unpredictable external electrical currents.
Always use a grounded 3--wire electrical cable
and connector to plug into the power line.
Closely follow the instructions on the Finometer
on screen help slides. In particular selecting a
proper sized cuff and the correct placement of a
cuff on a finger are critical for success.
Do not wrap finger cuffs around a toe or the wrist
of an infant. Accuracy of measurement on a toe
has not been established. An inflated finger cuff
applied to the wrist causes congestion of blood
in the distal circulation of the hand, which may
become painful and restricts distal oxygenation.
The zero adjustment or nulling of all pressure
transducers built--in is automatic, except for the
pressure transducer of the height correction system for which nulling has to be performed man-
•
•
•
ually (see section 4.4 on page 39). It is the responsibility of the operator to periodically check
the zeros and sensitivities of the transducers. Finometers leave our premises with carefully calibrated transducers. Immediately after transport, and at any time that the instrument is
dropped or otherwise damaged the zeros and calibrations should be rechecked. These checks are
quick and easy to perform (see section 7.1 and
following sections, beginning on page 67).
For safe and reliable operation and optimal accuracy only use FMS cuffs and only use data downloading software approved by FMS, Finapres Medical Systems BV.
Externally generated analog signals coming from
other devices, such as respiratory signals and
ECG’s can be connected to the Finometer for
recording. Furthermore, personal computing
equipment can be interfaced to the digital I/O
port of the Finometer for downloading of signals and data, and for remote control. Connected equipment has to meet the IEC specifications
(IEC 601 for electromedical devices or IEC 950
for data processing devices). The configuration
has to meet the IEC system standard (IEC 601-1--1). He who connects such additional devices
is responsible for adherence to the IEC 601--1--1
standard.
Complete specifications of Finometer are listed
in appendix A beginning on page 97.
2 To a quick start
This chapter describes step by step how to make a first measurement with Finometer, how to obtain the
resulting packet file, and how to sample an external signal during a finger pressure measurement.
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2.1
2.2
2.3
2.4
2.5
2.6
Setting up Finometer
20
A first measurement
21
Accessing the packet file
22
Sampling external signals
23
External offset and sensitivity
24
Save & recall the configuration
25
2.1 Setting up Finometer
Before you start a first measurement please read the
“Warnings, cautions and protective measures” chapter on page 15. Then do the following (Omit all
steps marked with I/O dealing with the analog I/O
box if you have no immediate interest):
1.
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5.
Connect the power cable at the rear of the Finometer.
Plug the power cable into a grounded AC power
outlet.
Switch Finometer on, the switch is at the rear.
You should see a display like that shown on this
User’s Guide front cover.
Observe the error message that may show up
above the Finometer picture on screen, see
figure 5.2 on page 45. Disregard any gray colored ones. There should be no yellow or red colored errors. Contact FMS if there is, see page 3.
Take the Finometer frontend box and cable,
figure 2.3 on page 21, and insert the big connector straight into the receptacle at the Finometer front bottom left, facing page upper panel.
The red dot should point upwards. The connector must go in straight and smoothly and must
be seated firmly. By pulling at the cable try to
6.
7.
8.
9.
pull the connector out. This should fail.
I/O Take the analog I/O box, facing page, and
connect it to Finometer at the rear. The chassis
connector part that fits is marked “Analog I/O”.
I/O In the Start display start the Square wave
cal calibration signal by pressing its button
twice, once to select and once more to activate.
You should see a display as shown in figure 5.3
upper panel on page 46.
I/O Connect an oscilloscope in turn to each of
the 4 analog output BNC connectors. They are
the bottom four connectors in the lower figure on
the facing page, marked output 1 through output 4. Check that the signal on the oscilloscope
screen matches that on the Finometer Start display.
Start the Finometer-clinique instrument by
pressing its button twice. You should see a display like in figure 8.2 on page 82. The Clinique instrument starts a square wave calibration signal which will run until a measurement
is started.
Your system is set up. It is time to turn to your
patient.
2.2 A first measurement
Next, attach to your patient two sensor systems, the
finger cuff and the hydrostatic height sensing system
(Omit all steps marked with I/O dealing with the
analog I/O box if you have no immediate interest):
8.
9.
1.
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Strap the frontend box to a subjects hand or
wrist. The cable should run away from the fingers and along the arm.
Select a properly sized finger cuff, see figure 4.2
on page 35.
Wrap the cuff as shown in figure 4.3 on
page 36. Note that finger cuffs have a conical
form. Gently try to remove the finger cuff by
pulling. This should fail.
Connect the hydrostatic height sensing system,
see facing page top panel. Insert its electrical
connector at the rear end of the frontend box in
the telephone chassis part, facing page bottom
panel.
Null the hydrostatic height correction system. Follow the instructions of figure 4.5 on
page 39.
Position and attach both height sensors as shown
in figure 4.5, the pillbox sensor at heart level.
In the Clinique display note that the button
marked [Gender] is highlighted. Press the 4
button until the correct gender is shown.
10.
11.
12.
13.
14.
Press . once so that the button marked [Age]
is highlighted, then 4 or 5 until the correct
age is shown. For the moment, disregard the
buttons marked [Height] and [Weight].
Press start/stop once to start a measurement.
Note that the on screen control buttons change
color and change function.
Continue the measurement for some minutes and
move the hand gently in height. If the height
correction system was connected and properly
nulled you should observe no effect. If not connected a substantial level shift should show in
the curve displayed.
I/O Connect the oscilloscope to analog output 1.
A finger blood pressure waveform should show.
I/O On analog output 2 the height correction
signal should show if this system was connected
and properly nulled. Gently move the hand in
height and observe the changed height level.
Press start/stop once to stop the measurement.
Press // and .. simultaneously until a message appears asking you to confirm exiting the
Clinique instrument. Press start/stop to confirm. You will be returned to the Start display.
You have just successfully completed your first measurement with Finometer.
2.3 Accessing the packet file
Each Finometer--research or Finometer--clinique finger blood pressure measurement automatically results in a packet file, of 1 kB per second of measurement. This file is stored internally in Finometer. The
Finolink program allows access to and downloading
of such files from a remote PC. The Finolink program
is described in its chapter in the Beatscope 1.1 User’s
Guide. To download a packet file:
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Get the so--called “null modem” cable coming
with Finometer. Any other such cable will do
too.
Connect it to Finometer at the rear. The proper
chassis connector is marked “RS232”.
Connect the other end to your Personal computer. Use a free COM port. Usually a PC has two
COM ports. Finolink can be configured to use
any available port.
Start Finolink by double clicking on its icon. The
display on the facing page is shown.
Select the button marked ‘Download’ and click
on it. The second display on the facing page
should show.
Click on ‘Configure’, then ‘Serial port’, and select the desired COM port. Click on ‘Select’.
7.
Click on ‘Connect’ and Finolink will start downloading the file name directory in Finometer.
Wait until finished.
8. Click on ‘Time’ to sort the list on time. Possibly
click a second time to reverse sort order and to
have the most recent file at the top.
9. Click on the top file to select it.
10. Click on ‘Local files’ to select a destination directory.
11. Click on ‘<’ to start the file transfer. Wait until
finished.
12. Quit Finolink.
The file just made has been transferred to your PC in
the subdirectory of your choice. The file name follows
the date/time convention explained in section 7.9
on page 75 that is generated automatically. A packet file can be renamed with Finolink before it reaches
the PC, or afterwards but not inside the Finometer
to assure greatest data integrity. Finolink can also
unpack the packet file to the earlier FAST system’s
header, results and samples files. This facilitates the
continued use of your own software in the manner you
are used to.
2.4 Sampling external signals
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Assume a comparison is to be made between a finger
and an intraarterial blood pressure recording. For
this purpose both signals need to be sampled simultaneously. Finometer records its plethysmographic
waveform on channel 4, but there is no interest in this
signal for the present study. Connect the intraarterial blood pressure signal to input--4 of the analog I/O
box. The following steps remove the plethysmogram
from channel 4 and replace it with the desired external input--4 signal (Note: The plethysmogram is still
present internally and is still evaluated, it is just not
stored in the packet file.):
5.
6.
7.
8.
9.
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If not already done switch on the Finometer.
From the Start display select Finometer--research by pressing the [Finometer--research] button twice, once to select, once to activate.
Press the [Configure] button. The arm cuff air
pump will start automatically and continue until
the full buffer pressure is reached.
Press 5 until the section external signals
is highlighted.
Press / to reach the Channel-nr column.
Press 4 or 5 until channel number 4 is highlighted.
Press / to reach the Source-mV column.
Press 5 to select external for that channel.
Note that the signal channel display just above
the Source mV--meter, facing page top display,
changed to show Ext 4. At the same time the
calibration waveform is removed from the analog
output 4 BNC connector and replaced by the
digitized input--4 signal.
Connect your signal source to input--4 on the
analog I/O box, assuming the box is still connected from the previous recording, section 2.1.
The green lettering on black background Source
mV--meter (facing page top display) indicates the
voltage read on channel 4. The input signal must
be within ±5 V.
2.5 External offset and sensitivity
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The external signal may not comply with the Finometer internal standard sensitivity of 100 mmHg/V and
offset equal to 0 V. To remedy there are two possible ways to go. Both routes can be taken as long
as the input signal amplitude remains within ±5 V.
The first is simplest. Just accept any offset and sensitivity that the external signal source has, but record
a calibration signal, and use the recorded signal to
calibrate afterwards in software yourself.
The other route is to let Finometer digitally preprocess the input signal by adjusting zero offset to 0 V,
and sensitivity to 100 mmHg/V, the values used in
Finometer. In that case follow these steps:
1.
Apply a voltage to the input--4 BNC connector
that represents a pressure of 0 mmHg.
2.
3.
4.
5.
6.
7.
Press / once to reach the Offset-mV column.
Press 4 or 5 until the Source mV--meter reads
0, see figure 2.5.
Next, apply a known voltage to the input--4 BNC
connector, here for example 1.033 V, equivalent
to 100 mmHg, see figure top panel, here performed on channel 1.
Press / once to reach the “Sensitiv-0/00 ” column.
Press 4 or 5 until the mV--meter reads
1000 mV, see figure bottom panel. The sensitivity is now reduced to 9670/00 or 0.967.
In case the input signal polarity is reversed with
positive pressures producing negative voltage excursions, change the polarity in the left most column and repeat adjusting offset and sensitivity.
2.6 Save & recall the configuration
After the effort to setup external channels you may
want to store (to later reload) this information in
the case that the set up is stable and will be used
frequently. Do the following:
1.
2.
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3.
4.
5.
Press the [Configure] button.
miscelPress 5 several times to select the
laneous section.
Press / twice to reach the Save config select
column.
Press 5 to select a configuration color, say Blue.
Press the [Configure] button to save this configuration, as suggested by the blue instruction on
screen. The configuration is saved under Blue on
disk and can be recovered at another occasion.
At the next occasion reload the blue configuration as
follows:
1.
2.
3.
4.
5.
Press the [Configure] button.
miscelPress 5 several times to select the
laneous section.
Press / once to reach the Load config select
column.
Press 5 to select the Blue configuration color.
Press the [Configure] button to load this configuration.
You are now ready for another finger pressure measurement recording an external pressure on channel
4. Press start/stop to start.
3 Introduction
This introduction presents a general description of Finometer in terms of methods used—with literature
references, features, available derived parameters from the blood pressure and flow waveform, and bias and
precision of the principal parameters: blood pressure levels and cardiac output.
3.1
3.2
3.3
3.4
3.5
3.6
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What is Finometer?
27
Methodology
28
Features
29
User interfaces
30
Derived parameters—beat--to--beat
Bias and precision
32
31
3.1 What is Finometer?
Finometer, like Finapres TM is a noninvasive hemodynamic cardiovascular monitor based on the measurement of finger arterial pressure. It is the successor
to the TNO Finapres--model--5 which has been the
basis of many methodological papers and space flight
models, and of the Ohmeda Finapres 2300e, no longer
available.
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Finometer has more options than its predecessors,
and can be used as a noninvasive hemodynamic monitor for trending of many arterial hemodynamic parameters. Yet, once set up it is still possible to wrap
a finger cuff and start a measurement by pressing the
start/stop button.
3.2 Methodology
The Finometer succeeds the popular Finapres TM device which was marketed by Ohmeda for many years.
Whereas Finapres meant finger arterial pressure, Finometer means Finapres with bias and precision and
tracking against intrabrachial artery pressures improved so that it approaches an intraarterial brachial
measurement in accuracy. To achieve this goal Finometer includes the methodological advances developed and published by TNO in cooperation with the
Academic Medical Center of the University of Amsterdam, the University of Florence Italy, and the
Erasmus University of Rotterdam over several years.
Some technology developed for the Portapres ambulatory finger blood pressure recorder is also included.
For references see appendix E on page 126.
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1.
2.
3.
4.
Continuous monitoring of the finger arterial pressure waveform with the volume--clamp
method of Peňáz 17 and the Physiocal criteria of
Wesseling 23, as in Finapres.
Reconstruction of brachial artery pressure waveform and level from finger pressure via generalized waveform inverse modeling 6, 7.
Automatic individual Riva--Rocci arm cuff return--to--flow pressure level calibration. 2
Stroke volume and cardiac output monitoring
with the Modelflow modeling method, 21 simulating a nonlinear, self adaptive, three--element
arterial model fed with a finger pressure wave to
output an aortic flow waveform similar to ones
measured with US Doppler or EM flowmetry.
3.3 Features
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•
Three instruments embedded in one hardware
environment:
− Research interface offering finger arterial
pressure recording with flexible displays and
all options;
− Clinique interface offering finger arterial
pressure recording with fixed display and a
few options;
− Classico interface offering upper arm auscultatory blood pressure with computer controlled cuff inflate and deflate and three types
of read out.
Three finger cuff sizes, fitting most patients
above the age of 6 years.
Low sensitivity to motion artifact.
Automatic hydrostatic height correction that
can adjust finger pressures to heart level.
26 cm (10 inch) diagonal, bright color TFT-LCD display featuring excellent viewing angle,
crisp, highly visible waveforms, selectable trend
displays, and large numerical readouts.
On screen, off--line graphics help pages showing
front panel operation, cuff application and hydrostatic height sensing.
On screen, on--line operator manual available.
Front panel mark button with markers entered
in the data file for easy reference.
24 hour internal storage of all recorded data
available for remote downloading to a PC, with
provided Finolink software.
On--line real time remote downloading of the da-
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ta stream with Finolink.
Remote control of important Finometer--research instrument functions via Finolink.
Sampling (at 200 Hz) of maximally four externally provided analog signal inputs.
Four analog signal outputs.
Square wave and pressure wave calibration signals available on the four analog signal outputs.
Displays configurable in medical units (mmHg)
and SI units (pascal).
Once configured the configuration can be stored
for easy recovery.
Upper arm Riva--Rocci cuff with automatic fast
inflation and slow, linear deflation and return-to--flow systolic pressure detected by the finger
cuff distal to the arm cuff, with the systolic pressure level used to calibrate finger pressure.
Calibrated reconstruction of continuous brachial
artery from the finger arterial pressure wave.
Cardiac output computed continuously from arterial pressure by simulating a nonlinear, self-adaptive model of human arterial circulation.
Fourteen beat--to--beat derived parameters computed from pressure and modelled flow waveforms are stored and available for trending.
User’s Guide available in paper and interactive
form.
Flexible postprocessing with the BeatScope software package.
3.4 User interfaces
Three user interfaces are available in the Finometer
by simple softkey selection. These user interfaces configure the display for the convenience of the user.
1.
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Finometer--research instrument offering full display programmability, consisting of three preprogrammed configurations (full featured Finometer, original Finapres, slave monitor using externally supplied analog pressure waveforms) and
2.
3.
two user programmed configurations. Configurations are color coded.
Finometer--clinique instrument with fixed displays and limited features and supreme ease of
operation.
Finometer--classico instrument providing a Riva--Rocci auscultatory blood pressure device
with automatic fast upper arm cuff inflation and
controlled linear deflation.
3.5 Derived parameters—beat--to--beat
Default, the pressure waveform is processed with two
automatic generalized procedures. These procedures
reconstruct a brachial artery pressure (reBAP) from
finger pressure (FinAP):
1.
2.
generalized finger to brachial waveform filtering, 6 and
generalized level correction. 7
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Default, 1 the following parameters are derived from
the reconstructed brachial artery pressure waveform:
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Furthermore, an individual patient level adjustment
called “calibration” can automatically be obtained
by a return--to--flow systolic pressure measurement. 2
Highest precision in blood pressure readings is obtained only after this calibration.
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SYS systolic pressure as the maximum pressure
in arterial systole,
DIA diastolic pressure as the low pressure just
before the current upstroke,
MAP mean arterial pressure as the true integrated
mean pressure between the current and the next
upstroke,
IBI pulse interval as the time between the current and the next upstroke,
HR pulse rate derived from the pulse interval,
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LVET left ventricular ejection time as the time
between the current upstroke and the dicrotic
notch,
SV stroke volume as the true integrated mean of
the simulated flow waveform between the current
upstroke and the dicrotic notch,
CO cardiac output as the product of stroke volume and heart rate,
TPR total systemic peripheral resistance as the
ratio of mean arterial pressure to cardiac output, assuming zero venous pressure (at the right
atrium),
D/SPTI diastolic to systolic pressure time index
ratio as an index of cardiac oxygen supply and
demand, always computed off a reconstructed
aortic pressure waveform,
PS*HR time--tension index (rate pressure product) as an index of cardiac oxygen demand, computed as the product of systolic pressure and
pulse rate,
dp/dt maximal steepness of the current upstroke
always computed on the finger pressure waveform,
Zao ascending aorta characteristic impedance at
the current diastolic pressure,
Cwk total arterial compliance at the current diastolic pressure.
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When the default reconstruction option is de--selected all parameters except two (D/SPTI and dp/dt) are obtained directly from
finger arterial pressure. The return--to--flow calibration procedure is then unavailable. Stroke volume and cardiac output are not
affected.
3.6 Bias and precision
Bias is the mean difference between value pairs obtained with two different methods of measurement of
a parameter and precision is the standard deviation
of the differences.
Level
systolic
diastolic
mean
bias
+4
+1
+1
(precision)
(7)
(5)
(5)
3.6.1 Arterial pressure
Finger arterial pressure (FinAP) shows waveform distortion and pressure decrements when compared to
brachial artery pressure (BAP) leading to bias and
imprecision. Compared to intrabrachial artery pressure the bias and precision are:
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Level
bias
(precision)
systolic
diastolic
mean
+1
−8
−10
(11)
(8)
(7)
Table 3.1 Differences
tween FinAP and BAP.
(mmHg)
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Numbers vary somewhat per study but the ones listed
are probably a fair resume. 12
After waveform reconstruction and Riva--Rocci return--to--flow level calibration a reconstructed brachial artery pressure (reBAP) results with reduced
errors:
The results are within the AAMI specification 1 which
Table 3.2 Differences (mmHg)
tween reBAP and BAP.
be-
requires bias to be less than 5 mmHg and precision
to be better than 8 mmHg. Clearly, waveform reconstruction reduces finger pressure uncertainty. 2
We have no data accumulated according to the BHS
protocol in comparison with Riva--Rocci/ Korotkoff
upper arm auscultatory pressure levels. Since auscultatory pressures differ systematically from intrabrachial levels (our reconstruction goal), we cannot
expect that reconstructed brachial artery pressure
levels will meet BHS auscultatory criteria closely.
3.6.2 Cardiac output
The Modelflow method used in the operating room
with intraradial artery pressure has +0.3 `/min bias
and 20% precision compared to thermodilution cardiac output. It can thus not replace thermodilution
as a monitor of absolute levels of cardiac output.
Once calibrated its bias is zero and precision is 8%. 13
as is
calibrated
bias
(precision)
+0.3
−0.1
(1.0)
(0.5)
Table 3.3 Differences (`/min) between
Modelflow and thermodilution C.O..
Thus, in tracking percentage changes it can replace
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a triple random thermodilution or any other clinical method presently in use. In addition, using noninvasive finger pressure instead of intraradial or intrabrachial pressure does not appear to reduce Modelflow tracking precision. 9
4 Help slides
Full screen help slides in Finometer are reachable from the Start display. Press the Help slides associated
button twice, then 5 repeatedly to view the slides in order:
1.
2.
3.
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4.
5.
6.
7.
the cuff sizing slide (section 4.1) shows how to select a properly sized cuff for a finger;
the cuff wrapping slide (section 4.2) shows the correct manner to wrap a FMS finger cuff, plus three
ways of incorrect wrapping;
the height sensing slide (section 4.4) presents the two simple steps towards a well nulled system, and
shows proper sensor placement;
the front panel slide (section 4.5) explains the functions of the Finometer control buttons;
the correction slide (section 4.6) presents the finger to brachial inverse modeling methods through
generalized filter and correction equation;
the calibration slide (section 4.7) presents the effect of an individual patient return--to--flow systolic
calibration in reducing bias and improving precision;
the available software slide (section 4.8) explains briefly which instruments can be selected to run in
Finometer.
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The Start display (figure left) honors two pioneers of blood pressure measurement: Landois, who demonstrated
for the first time the importance of the pulsatile component present in the blood pressure which had been
masked in earlier methods by sluggish instrumentation, and Riva--Rocci who invented the arm cuff method
which has proven so simple and reliable. The ideas of reliable cuff measurement and of faithful recording of
pulsatility are present in Finometer. For historical notes honoring Professor Jan Peňáz, 17 the inventor of the
servo--plethysmomanometer device, which lies at the root of Finapres, Portapres, and now the Finometer, see
Wesseling. 20
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Cuff selection & handling slide
35
Cuff and frontend mounting slide
36
Difficult situations
37
Height sensor nulling & placement slide
39
The Finometer front panel buttons slide
40
Waveform modeling & level correction slide
41
Level calibration by return--to--flow slide
42
Finometer instrument selection slide
43
4.1 Cuff selection & handling slide
The finger cuff is the sensory organ of Finometer.
It is in contact with the patient’s finger to detect
the smallest changes in finger artery size, at high
speed, and to control cuff pressure to oppose even
subtle changes in arterial pressure dynamically. Handle these sensors with care and they will provide years
of useful service.
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Selection of a proper size cuff is easy if finger circumference can be measured in centimeter. A table
lookup refers to the proper size. Otherwise you might
use the indications of a proper fit that are shown in
the slide.
To prevent damage to a finger cuff:
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•
Do not remove the finger cuff from a finger before the measurement is stopped and the air hose
is disconnected from the frontend. Even though
Finometer automatically deflates when the finger
cuff unwraps, the bladder may still become damaged.
• Do not apply air pressure to a finger cuff when
it is not wrapped around a finger or other solid
object. This may damage the finger cuff bladder.
• Do not flatten finger cuffs by in-- or outward bending since this may damage the electrical connections, the bonding of materials, and the electrical
shielding. Finger cuffs are preformed around a
conical mandrel during manufacture and best remain in this shape.
• Do not attempt to repair a defective finger cuff
since this will substantially affect measurement
accuracy.
4.2 Cuff and frontend mounting slide
Finger cuff positioning is shown in the figure in four
ways, three of which are incorrect. It is important
This is the mounting order that seems to work best:
1.
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that the conical cuff matches the conical finger,
that both knuckles are covered equally,
that the cuff mounted plethysmograph sees the
finger arteries well, and
that the cuff leaves no undue space between it
and the finger.
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2.
3.
4.
5.
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Figure 4.4 Click on figure to start a movie on finger cuff positioning.
Strap the frontend box to the back of the hand
or the wrist.
Place the finger cuff as shown in the slide. The
index, middle and ring finger are often your best
choice. Measurements on a thumb are possible
when the shape of the thumb is acceptable.
Lead the cable and air hose between two fingers
to the frontend box.
Match the red dots on the frontend receptacle
and the cable connector and insert the connector
as deeply as it will go.
Firmly insert the Luer attached to the air hose
to achieve a tight seat.
4.3 Difficult situations
Obtaining finger pressure readings can be difficult at
times, when patients feel uncomfortable, sense a cold
draft, are nervous, are cold, are in pain, or underfilled,
or under light anaesthesia.
4.3.1 Cold fingers
Differing somewhat per study, 95 to 100% success in
recording acceptable blood pressures is usually obtained in nonanesthetized patients. Special measures
have to be taken to get readings in the remaining few
percent. Here are the actions that we found to have
success, in no particular order:
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5.
Take the patient’s hand in your own warm hand,
speak a few comforting words, explain about the
device and how it behaves.
Try the right (dominant) hand; it tends to have
a higher pressure in the finger.
Wrap a warm--colored towel loosely around the
hand with the cuff. Place the hand simultaneously on a warmed pad or rubber flask filled with
warm water. Cover the other hand as well.
Raise the hand above the head for at least one
minute. One minute is the time constant for arterial smooth muscle tone to relax. Then lower
the hand to heart level and start a measurement.
Let your patient stand up and spread out their
arms. Then make a forceful horizontal circular
motion where you start with your arms spread
out, to move them rapidly (centrifugal force) to-
6.
7.
8.
wards each other and let them slap on the opposite sides of the back. This forces blood into the
hands. Repeat several times.
Blow warm air onto the back of the neck.
Have the person wear a sweater, have no arms,
shoulders, neck exposed.
Avoid air conditioning with cold air drafts coming from any side.
4.3.2 Arm arterial sclerosis
Arteriosclerotic plaques in subclavian, brachial and
radial arteries do not occur with great frequency, even
in elderly patients. In cases when the finger pressure
wave appears damped or has unexpectedly low systolic and diastolic levels, or when a return--to--flow
systolic calibration procedure causes level corrections
greater than +15 mmHg over and above the level
correction already applied automatically, it is recommended to switch to the other arm to see if conditions
improve. When a finger pressure curve is seriously damped a message will appear immediately above
the pressure pulse display, alerting to this condition.
4.3.3 Costo--clavicular cutoff
Infrequently, in some patients the subclavian artery
may become compressed between the ribs and the
clavicle. The result of this compression is a damped
pulse or a completely occluded artery and no pulse
at all, in which case Finometer cannot start. When a
patient reports about frequent occurrences of numbness or tingling sensations in the fingers this is often
an indication that such compression can be present.
The condition is easily remedied by changing the position of the arm until a pulse is palpated at the wrist.
4.3.4 Cyanotic finger tips
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Using finger cuffs cyanotic finger tips often become
visible after several minutes of monitoring. Obviously, venous congestion distal of a finger cuff does occur
and the venous blood visible in the plexuses appears
as a blue or a pink coloring of the skin. A pink color
is seen at a high degree of arterialization of the congested blood. In addition, numbing of tactile sense
is occasionally reported by some patients. Upon removal of the cuff, reddening of the skin under the cuff
always occurs. All phenomena disappear within a few
minutes after the measurement is stopped, suggesting that the method can be tolerated for very long
periods without harm. No obvious swelling of the
fingertip is observed and no long term effects have
been reported. Keeping the fingers and hand warm
during the measurement improves finger tip arterialization tending to change finger tip color to pink and
reducing the rate of occurrence of numbing the tactile
sense.
The theory of this is as follows: The arteries un-
der the finger cuff are dynamically unloaded and the
arterial walls float steady at their unstressed (slightly
smaller than normal) diameter. The unloaded arteries still have about 60% of their original distended
diameter. The veins under the cuff are collapsed and
block venous return flow. The finger tip distal of the
cuff thus contains a pool of blood in arteries, arterioles, capillaries, venules and veins all at arterial pressure. During systole blood flows in through the open
arteries under the cuff filling the distal circulation
and raising the pressure. Since this blood is arterial
it partially refreshes the congested venous blood. In
diastole some congested blood leaves the distal finger tip through the still open arteries in a retrograde
direction. This process is more thorough the easier
the blood can fill and empty the finger tip circulation. When in-- and outflow is so easy that it reaches
the venous blood in the small veins below the skin
the finger tip is seen to color pink. When in-- and
outflow is compromised due to arteriolar constriction
the finger tip colors blue. Relaxed arterioles can be
seen frequently during normal sleep.
Gravenstein, et al. 8 reported a substantial capillary
oxygen pressure remaining in the finger tip distal of
a Finapres cuff of from 49 to 58 mmHg compared to
about 80 mmHg normally and Pulse Oximeter saturation of about 93% with much variability. Interspersing regular rest periods of 30 s every 5 minutes
during 30 minutes of monitoring did not improve capillary oxygen partial pressures.
4.4 Height sensor nulling & placement slide
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Blood pressure is referred to heart level since Hales.
The upper arm Riva--Rocci cuff is almost always near
heart level, but a finger cuff is not. Thus, to sense
the position of the finger with respect to the heart,
a height correction system is included in Finometer.
It has a sensor to be placed at heart level and another at the finger. The height of the liquid column
between the sensors is measured by a pressure transducer and automatically subtracted from the finger
pressure. Sensor placement and sensor nulling require
some attention.
4.4.1 Nulling
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Height system nulling normally is automatic from its
previous value. This null is essentially stable but may
show some drift with time. It is best, therefore, after
the Research or Clinique instrument has been selected
and activated, to check the height null before starting
a measurement. Follow the instructions on the help
slide (facing). Furthermore, renulling is required if
the height correction unit was removed and reinserted
or if another height correction unit is connected. An
on screen message alerts the operator to it. See the
depicted procedure.
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4.4.2 Sensitivity
The sensitivity (the gain) of the height correction sys-
tem may also show drift. This drift may have varying
causes and cannot be adjusted in the field. It can,
however, be checked as follows.
1.
2.
3.
4.
5.
From the Finometer--Start display start the Finometer--research instrument by pressing [Finometer--research] twice, it is the left most button under the display.
Press [Configure] once, it is the right most button
under the display; if [Configure] is not shown
you are doing a measurement and cannot check
height.
Press 4 or 5 to select ”transducer check”.
Press / and 5 to select ”height”. This card
shows a display of relative transducer height expressed in cm.
Follow the blue instructions displayed on the
card.
If the sensors are held 100 cm apart vertically, and the
indicated height is only 90 cm, the system has a 10%
error. This unit should be replaced. In the case that
no replacement is available, it is best to keep the hand
close — within 20 cm — to heart level. In that case a
hydrostatic height difference of no greater than 20 cm
is associated with an error of less than 2 cm (10% of
20 cm) water column or 1.5 mmHg in blood pressure
for the defective unit, which is often acceptable.
4.5 The Finometer front panel buttons slide
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Finometer embodies three instruments in one device,
the Research, the Clinique, and the Classico instruments (section 3.4 on page 30). The Clinique instrument has a simplified interface without tab cards.
The descriptions below and facing, therefore, apply
only partially to the Clinique instrument. The Research and Classico instruments, however, do have
tab cards to select options, to enter patient information, to configure displays. Their function is as
follows:
•
•
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the selection/confirmation buttons immediately below the display jump to the associated on
screen tab card or button,
the // and .. double arrow buttons move
between on screen tab cards or buttons,
the / and . arrow buttons move between
columns on a tab card, they thus have no function in the Clinique instrument,
the 4 and 5 arrow buttons move between dis-
•
•
played selection or change a displayed value,
the mark button places a marker in the results
file and in the trend display,
the start/stop button starts or stops a measurement.
The mark button also serves to null the height correction system when no measurement is ongoing. It
is recommended, however, to use the {Configure}
card in the Research instrument since it additionally allows the checking of system sensitivity, see
section 7.3 on page 69.
A special extra function is activated by pressing
the // and .. buttons simultaneously. This
allows to EXIT the currently running instrument
and to return to the Start display.
4.6 Waveform modeling & level correction slide
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Finger blood pressure pulsations are tens of milliseconds delayed with respect to intrabrachial ones
since they travel farther. In addition, their levels are
generally lower, and the waveforms appear more distorted 7. When we studied these distortions in detail
it appeared that they can be explained by a generalized “forward (i.e. brachial to finger)” transfer function or linear filter effect 6. Clearly, low frequencies in
the brachial pulse, those below 2.5 Hz, are attenuated and higher frequencies are amplified, in particular
those near 8 Hz. This is shown in the figure, left
panel thin curve.
Although this transfer function is not the same for
each subject the differences are so small that the distortion can be explained with little error by a single
generalized transfer function. To correct distortion
we thus could design a “reverse (i.e. finger to brachial)” or inverse filter with a shape such that the
natural, forward transfer function is precisely compensated. This inverse filter’s response is shown as
the thick line in the figure. It emphasizes lower fre-
quencies and has an anti-resonance near 8 Hz.
The original and the resulting inverse filtered finger
pressure pulses are shown in the figure, right panel
upper two boxes. The delay in the finger pressure
we did not compensate. After inverse filtering both
waveforms are nearly identical in shape, but the pressure levels are not compensated well.
Thus, we also studied the differences in the systolic,
diastolic and mean pressure levels 7. It appeared that
pulse pressure was correct on average after inverse
filtering but that all pressure levels were high. Using the inverse filtered systolic and diastolic levels we
next developed a generalized level correction equation
to return level differences to near zero on average, although not too well individually, and to slightly reduce the standard deviation of the differences 7. The
effect of generalized level correction on the pressure
pulses is shown in the figure, right panel bottom box.
In this particular case correction is nearly perfect but
this is not always so.
4.7 Level calibration by return--to--flow slide
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The level of the finger pressure waveform after generalized correction, statistically, is not or
is only marginally within AAMI requirements 1,
section 3.6.1 on page 32. That situation can be
improved by performing an individual upper arm cuff
systolic calibration 2. For this purpose an arm cuff is
wrapped on the ipsilateral arm and automatically inflated and deflated by a computer system upon operator command. When arm cuff pressure is suprasystolic no pulsations can be sensed in the finger. The
first pulsation that passes under the arm cuff signals
return to flow. It is sensed in the finger and detected
by software. Arm cuff pressure is read at that instant and the reconstructed brachial pressure of the
previous section is further shifted in level by an individual amount thereby improving bias and precision
substantially, page 32.
It is not clear at present if and when this calibration
needs to be repeated although there are indications
that the inverse filter and generalized level correction
take care of the variability over time in finger pressure
levels with respect to brachial. If this were true under all conditions a return to flow systolic calibration
would not need to be repeated. Presently, however, we recommend that the calibration procedure is
repeated at each major change in hemodynamics.
4.8 Finometer instrument selection slide
In the Start display softkeys allow selection of one of
three instruments by pressing its associated button
twice, once to select and once to activate. Once an
instrument is running return to the Start display is
by pressing // and .. simultaneously. When in
a measurement, however, stop it first by pressing the
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start/stop button.
The distinguishing features of each instrument are
described briefly on the slide, on page 6 and in
section 3.4.
5 The Start display
When Finometer is turned on the Start display shows up after a few seconds (facing page). The TNO logo (see
under FMS and TNO in the Glossary D on page 117) is shown upper left, a copyright note upper right.
The copyright note also presents the software build date as year and day--number of the year: (C) 2001.083
TNO, meaning the 83--rd day of the year 2001. At the screen bottom six soft keys are available, operated by
the hardware buttons just below, from left to right: [Finometer research], [Finometer clinique], [Help
slides], [Square wave cal], [Pressure wave cal], and [Finometer classico].
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The [Help slides] button is preselected. When you are new to finger pressure measurement with Finometer
please take some time to scan these slides, or this guide from page 34. To activate the help slides press
start/stop or press the [Help slides] button once, then press 4 or 5 . Exit by pressing any other button,
for example start/stop .
From the Start--display the four analog output BNC--type connectors located on the analog input/output
(I/O) box can be supplied with a calibration waveform to calibrate subsequent analog or digital recording
channels. See page 46.
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A Finometer software instrument (Research, Clinique or Classico) is selected by pressing one of the below
screen buttons twice. Try and press the [Finometer research] button twice to start the Finometer--research
instrument. Once its display has been built up press the // and .. buttons simultaneously to return to
the Start display.
Finally, it is possible to off--line download the packet files stored in Finometer. To do this you have to run
the supplied so--called “null modem” cable between the serial I/O port marked “RS232” on your Finometer
and a COM port on a Windows PC. On the PC execute the Finolink program, select the COM port to which
you connected and you have access to all the data files stored in the Finometer without deleting any files on
the Finometer. For further details on the Finolink program please refer to the Beatscope 1.1 User’s Guide,
and for Finometer file storage and recovery to page 54.
5.1
5.2
5.3
5.4
The Finometer selftest
45
The calibration signals
46
Off--line downloading of stored packet files
Failure to start—rebuilding the index
48
47
5.1 The Finometer selftest
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The Finometer performs selftests to check if the embedded computer is still running and if essential hardware is in operating order. The result of these tests
is not shown unless an error is detected. In the figure
(facing page) all errors are listed. Gray errors can be
corrected easily, yellow errors are serious hardware
errors but affect only upper arm cuff operations, red
errors are serious hardware errors. If a red or yellow
error occurs, or if a gray error persists you should
contact FMS immediately (see page 3).
Frontend not connected:
If the frontend cable connector is not inserted in its
receptacle (see figure 2.1 on page 19) this gray error appears. The error should disappear after the
connector is inserted and seated firmly.
Height sensor absent:
If the hydrostatic height sensor’s electronic connection (see figure 2.3 on page 21) is disconnected the
gray error appears. Reconnect and the error should
disappear.
Height sensor not nulled:
When the hydrostatic height sensor is not present
at start up Finometer assumes that a new unit will
be used. In that case it asks the operator to renull
manually.
Armcuff xdcr out of order:
Arm cuff pressure is transduced by a semi--conductor
pressure transducer within the device. It is automatically nulled. When this automatic null is not achieved
the yellow error is signalled. Return--to--flow systolic
calibration of finger pressure is not possible.
Buffer xdcr out of order:
The arm cuff is inflated from an air buffer. Pressure in
this buffer is measured by a semi--conductor pressure
transducer. Upon failure of the transducer this yellow
error appears.
Internal ground fault:
Finometer cannot perform normally.
Power supplies not well:
A/D converter not well:
5.2 The calibration signals
The square wave calibration signal has been designed to allow for checking the
•
•
•
•
•
sensitivity,
zero offset,
signal polarity,
recording speed, and
dynamic response characteristics
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of a subsequent analog recording channel and to manually adjust sensitivity and offset or to automatically
program such adjustments at a later time. The signal moves between three levels: 0, +1, and +2 V,
spending 60% of the period at zero and 40% of the
period at either positive voltage level. Check polarity
on this 40/60% property. Five cycles of exactly 1 s
duration, or 1 Hz, or 60 BPM are generated first. All
these numbers are displayed on screen.
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Check the recording channel’s rise time and overshoot
at this 1 Hz frequency. Rise time should preferably
be less than 5 ms, overshoot ideally 0%. Next a single
10 s square wave is generated. This is well suited to
manually adjust your recording channel’s zero offset
and sensitivity, providing ample time for an operator.
If a recording channel is AC coupled, as may be the
case for an ECG recording channel, a rising baseline
and drooping topline should then be observable at
this slow speed waveform. Such a recording channel
is not suitable for blood pressure signals.
The same calibration square wave is present at the
analog outputs after selecting the Research and Clinique instruments. Before a measurement with these
instruments is started the calibration square wave is
automatically supplied to the four analog output connectors, and automatically removed when a measurement is started or a channel is configured as an external input channel, see section 7.7 on page 73.
The pressure wave calibration is a single, exactly repeating finger artery pulsation, recorded in
a young adult subject. Its systolic pressure level is
1295 mV, diastolic is 710 mV, pulse interval is 930 ms
(exact) and calculated heart rate 64.5 BPM. These
values are also displayed on screen. The signal amplitude is specified in millivolt (mV) and for Finometer 1000 mV corresponds to 100 mmHg. Thus S/D is
129.5/71 mmHg. Your pulse wave detection software
should be able to closely approach these values if the
recording channel has adequate dynamic response, no
offset, and correct timing and sensitivity.
5.3 Off--line downloading of stored packet files
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Each finger arterial pressure measurement that is
made with the Finometer Research or Clinique instruments is stored in a revolving store on disk. In
a full revolving store a newly arriving packet automatically overwrites the oldest packet present. A revolving store, therefore, does not have to be erased.
Finometer’s store can hold maximally 4096 files of
maximal total duration of 24 h, in 512 byte packets
of 0.5 s storage each. If these packet files are needed
for later analysis they can be downloaded off--line by
Finolink as long as not overwritten by new packets.
other way to download files.
To perform off--line downloading the Finolink program must be started on a Windows personal computer linked to Finometer via the so--called “nullmodem” cable supplied with the device. There is no
•
•
•
In the Research and Clinique instruments both on-line (while a measurement is running) and off--line
downloading are possible. In the Start display only
off--line operation is possible and measurements cannot be started while downloading. If an analog output calibration signal has been started, however, it
will continue.
For further details on downloading see
section 2.3 on page 22,
section 6.4 on page 54,
5.4 Failure to start—rebuilding the index
When the power plug was accidentally pulled during
a measurement the system does not have time to update the pointer index file (a directory like structure)
and to properly terminate files. At the next Finometer power--up this is detected by the software. The
situation is quite similar to improperly terminating
Windows. The system detects which files are OK
and which need reconstruction or recovering. You select the action to be taken and are asked permission
before any operation is started. If you decide not to
act because you want to contact FMS first (page 3),
simply press the mark button and the Finometer will
go into a state of hibernation. Switch power off and
on to wake up.
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This screen is shown initially:
Pointer file corrupted...
[F1] to recover lost file
[F2] to reconstruct pointer file
[F3] to start new empty pointer file
[mark] to escape
^^Which?
[F1] pressed: will recover lost file...
[start/stop] to confirm, [mark] to escape?
[start/stop] pressed: recovering lost file...
...
Lost data recovered.
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[start/stop] pressed: reconstructing pointers...
hr 0 ......
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...
hr 23 ......
Pointer file reconstructed.
Progress is shown by typing a . for each minute of
data packets reconstructed. Thus, per hour reconstructed 60 . are typed. Your interrupted data file
is also recovered (as far as it was written to internal
memory) and properly terminated. The total operation takes approximately 10 min. After successful
completion of either process return is to the Start
display to start a measurement.
The recommended approach is to first try [F1]. This
operation is fast and when successful does the trick.
When the recovery operation shows errors try [F2]
which will almost always work. Try [F3] if nothing
else works but the next time you do a measurement
you overwrite even recent earlier files. After this action is successful you may, therefore, want to try [F2]
again since no data file is yet erased, and still keep
previous files.
In summary, [F1] is fast and usually successful. [F2]
can always be done but is time consuming. [F3] is
also fast but destroys data files unless reconstructive
action is taken.
6 The Finometer--research instrument
The Finometer--research instrument was designed with a researcher in mind who is in need of full control of all
the options that Finometer offers. Even remote control of some functions is available. Yet, relative simplicity
of operation is maintained by grouping various options logically on Tab cards on screen. For example, the
entering of patient information is grouped on the second tab card from the left and data entry is not more
complex than selecting an information column on the card and pressing the 4 and 5 keys to select and
change a value.
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On--line context sensitive help is available. Press the [Help] button and the relevant help text appears. Press
the [Help] button a second time and a table of contents is shown. Use the 4 and 5 keys to highlight a
topic, then press the [Help] button once more to move to that help paragraph.
Five of the 15 derived parameters can be trended on screen of which three of the pressure parameters are
fixed. Convenient vertical and time scales can be selected by the pressing of a few buttons. Twelve derived
parameters are displayed numerically on the right most tab card, with values updated every second of time.
Four signal channels can be viewed, one at a time, with selectable vertical and time scales. A special calibration
tab card shows information on Physiocal (left side) and on return--to--flow calibration (right side), and pushing
a button turns either one off or on.
When not in a measurement, all pressure transducers in Finometer can be checked interactively for zero and
sensitivity. Furthermore, once you configured the screen display to your needs the configuration can be stored
by moving to the configuration tab card and saving under a “color”. Loading a configuration is just as easy.
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Running the Finolink program on a remote PC it is possible to place the Finometer near the patient with the
display closed. Connected via a serial cable an almost complete copy of the Finometer--research display can
be viewed on the PC screen. From the remote PC you may start and stop a measurement, turn Physiocal
off and on, start and stop a return--to--flow systolic calibration, place markers in the Finometer packets and
download this file at the same time.
After selecting and activating the Research instrument in the Start display a first screen is shown always with
the second tab card from the left {Describe subject} preselected. This should be interpreted as a reminder of
the importance of entering correct patient data first. Treatment of the Finometer--research tab card system,
however, is in the left to right order in which the cards appear on screen. The left most is the {Help} card.
In the accompanying texts the notation that is followed is:
?
?
a front panel button is marked by [ ],
an on screen tab card is marked by { }.
When a button is pressed its action is immediate. When by exception action is not immediate but a confirmation is needed this is always indicated by a message in blue lettering displayed on the tab card.
For example, when entering patient data on the {Describe subject} card, a message appears: Press [Describe] to confirm changes. Correct patient data is essential since the SV/CO/TPR values depend critically on it. Confirm, therefore, any changes made.
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6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
6.12
6.13
6.14
Entering patient data—research
51
Layout of the Research display
52
The error message display—research
53
Files downloading and remote control
54
The Help card
55
The Describe subject card
56
Setting a subject’s data
57
The pressure--volume diagrams
58
The Select trends card
59
Cardiac oxygen supply/demand
60
The Select A/D signal card
61
The Physiocal card
62
The Return--to--flow--cal card
63
The Derived variables card
64
6.1 Entering patient data—research
After starting Finometer--research the most noticeable line displayed is: “Enter Age and gender”.
Knowing the exact age and gender of the subject is
important information for an optimal pattern recognition, but is essential for setting up the Modelflow
simulation with correct model parameter values to
compute cardiac outflow.
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subject descriptive data by reselecting the {Describe
subject} card and changing the settings. In that case
part of the packet file will contain stroke volume and
cardiac output data computed with an incorrect patient description. In subsequent evaluations with our
Beatscope software this is detected and you are asked
if you want to recompute the results.
To change any of the displayed values:
Although to enter this information at the start is not
enforced, the first display screen draws attention to
the missing subject information and induces an operator to enter the patient data first. When a rapid
start is required or when the information is not available Finometer software assumes the current values
to be acceptable.
1.
2.
3.
4.
In the case that no gender is selected gender is shown
as decide and an intermediate setting is assumed.
In the Finometer--research instrument it is possible
at any time during the measurement to adjust the
5.
press / or . to move to the desired parameter
column on the tab card,
press 4 or 5 to change the value of the parameter,
press / or . to move to the other parameters,
and change their values,
press the [Describe subject] button below the
screen to enter the data,
check in the right model information display panel the entries
Pat:
BSA:
6.2 Layout of the Research display
The Research screen has five horizontal layers, from
the top:
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•
•
•
•
the software identifier and status line,
the (flow--)derived parameter trend display layer,
the pressure parameter trend display layer,
the miscellaneous information layer,
the tab card program control layer.
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The status line shows the TNO logo, the time, and
a copyright note. When an error occurs time is replaced by an error message which remains for 10 s.
During a measurement the copyright note is replaced
by the Physiocal state. The time display shows clock
time and time lapse since the start of the current measurement or when off--line the idling period. Clock
time can be adjusted via the {Configure} card date
and time section, see section 7.9 on page 75.
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The derived parameter layer left panel shows the
Modelflow curve. The vertical scale is from −250 to
+1000 ml/s. The horizontal scale is 1 s, with 0.1 s
tick marks. The middle panel is a trend display of two
selectable derived parameters, section 6.9 starting
on page 59. The dual numeric display shows two
trended parameters as eight--beat running averages.
The pressure parameter layer left panel shows
the processed pressure waveform. The vertical scale
is the same as in the trend panel. The horizontal
scale spans 1 s. The middle panel is a trend display
of the three pressure levels (S/D--M) measured on the
processed pressure waveform at the left. The vertical
and time scales are selectable, see section 6.9 starting on page 59. The dual numeric display shows
the eight--beat running average systolic and diastolic
levels.
The miscellaneous information layer left panel
shows todays date, the beeper state, the unit system,
the active finger cuff (1 or 2), the time lapsed and
the total measurement time available on this finger
before the next finger switch (here 3/30 min). Also shown are the current file name and size, and the
finger height (here −15 mmHg, which is below the
heart). The middle panel shows one of the four sampled signals that are also stored on internal memory.
Normally they are finger arterial pressure (FinAP),
finger hydrostatic height (Height), arm cuff pressure (Armcuf), and finger plethysmogram (Pleth).
An internal signal can be replaced by an externally
supplied signal for display and storage, if so configured, see section 7.7 on page 73. The right panel
lists patient information and model parameter values.
The three Modelflow parameters are framed in white.
BSA (body surface area) is according to Dubois and
Dubois.
The tab card instrument control layer is treated
in following sections.
6.3 The error message display—research
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Normally the top status line shows clock time and
time lapse since measurement start in green letters on
a black background. When an error occurs the time
display is replaced by an error message in red color. Typically, an error message signals a condition in
which Finometer cannot function properly and from
which it cannot recover automatically. The measurement is stopped and the error message is displayed
10 s. At the start 3 beeps are sounded, followed by
another 3 beeps after 5 s. After another 5 s the message disappears and another start can be attempted.
.
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.
.
.
.
.
.
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.
In the case shown the finger cuff air hose got dislodged
and must be reinserted. After the forward slash (/),
the procedure where the error was detected is named.
The message is also stored in the last packet of this
measurement’s file on disk. Here are some of the error
messages:
Error messages, unlike alerts or alarms, represent situations that are not considered dangerous. They have
to do with dislodged connectors, contracted finger arteries, or worn cuffs.
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Connect frontend/startAutolock
Check air supply/steadyPressure
Check armcuff air supply/fillRivabuffer
Unstable pressure/steadyPressure
No plethysmogram/failAutolock
Finger too thin/checkFrontgainDn
Check cuff cable/centerPlet
Connect cuff cable/checkLEDcurrent
Faulty finger cuff/setLEDcurrent
cuff--LED problem/checkLEDcurrent
For a list of annotated error messages see “Error
messages” on page 114
6.4 Files downloading and remote control
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made with the Finometer--research or clinique instruments is stored in a revolving store on disk. In a full
revolving store a newly arriving packet automatically overwrites the oldest packet present. A revolving
store, therefore, does not have to be erased. The files
can be downloaded off-line by a remote PC with
program Finolink. Files downloading can be done
while the Finometer is doing a measurement. This is
called on-line downloading. For on--line downloading you must start the Finolink program and click its
“Monitor” button, see figure 2.4 on page 22. This
is completely invisible to the Finometer operator.
Off--line files downloading was discussed briefly in
section 2.3 on page 22. Any measurement file
present can be selected for off--line downloading. It
requires full control over the Finometer packet store
so that no new packets can be stored. Thus, off-line files downloading and doing a finger blood pressure measurement are mutually exclusive. A warning
is issued in that case that a measurement cannot be
started, see facing page.
To start either form of downloading:
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2.
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Get a “null-modem” cable. There is one supplied
with your Finometer.
Plug one end of the cable into the Finometer
3.
4.
5.
6.
serial I/O connector marked “RS232”, located
at the rear.
Plug the other end into one of the PC serial ports
possibly labelled COM1:, etc. In the case that
the supplied cable is of insufficient length you
may extend it with ordinary (non-null-modem)
serial cable.
Start Finolink on the PC by double clicking on
its icon, or go via Beatscope.
If not done configure the COM port number:
click on ‘Configure’, the ‘Serial port’, and select
the desired COM port. Click on ‘Select’.
For on--line downloading click on “Monitor”. A
display is shown quite similar to the Finometer-research display. If the Research instrument is
running on Finometer you can control four of its
actions remotely:
• start and stop a measurement run,
• start and stop a return--to--flow upper arm
cuff cycle,
• turn Physiocal off and on,
• place a marker.
For details see the Beatscope 1.1 User’s Guide
Finolink chapter. These four items allow the remote operations that might be needed in case the
subject and the Finometer are not in the same
room as the experimenter.
6.5 The Help card
The Finometer--research instrument has more than
100 help paragraphs built--in. They explain some of
the methodology and ways to control the Research
instrument.
1.
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2.
3.
4.
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5.
6.
7.
Press the [Help] button once to bring up the
{Help} card to display the first help paragraph,
see facing page.
Press the 4 or 5 to display the previous or
next help paragraph.
Keep the 4 or 5 depressed to leaf through the
paragraphs in greater steps.
Press the [Help] button again to display a table
of contents.
Press 4 or 5 to highlight a topic of interest.
Press the [Help] button once more to jump to
the selected topic.
Press one of the other Tab selection buttons then
8.
press the [Help] button again to display help for
that {Tab card}.
Some {Tab cards} have subsections. Move to
the subsection and then press the [Help] button
to display more detailed help.
Throughout these help paragraphs
[]
{}
()
<>
signify
signify
signify
signify
Finometer front panel buttons,
tab cards,
miscellaneous information,
literature references.
Thus: [Help] -- a button, {Configure card} -- a tab
card on screen, (Files downloading) -- some miscellaneous information, <Langewouters> -- a literature
reference.
6.6 The Describe subject card
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Finometer provides for finger arterial blood pressure
measurement but the reason we searched for a noninvasive method to give us calibrated phasic blood
pressure waves around 1975 was that we needed it as
input to a pressure pulse contour algorithm to compute cardiac stroke volume and output. Later, as
a successor to pulse contour methods, we developed
the Modelflow method for computing a cardiac flow
curve. One of the reasons that Modelflow shows better precision than earlier pulse contour methods is
that it uses a patented, nonlinear, self-adaptive simulation model based on aortic hemodynamic properties measured never before with such precision by
Langewouters. 15
Langewouters showed that human aortic properties
were substantially nonlinear and that nonlinearity depended strongly on a subject’s age and gender, and
slightly also on height and weight. Hence the im-
portance of entering the patient parameters from the
start, so that the Modelflow method will be better
in estimating and trending stroke volume and cardiac output. It would be expected that properties
also depended on degree of arterio-sclerosis but it appeared from Langewouters’ studies that the stiffening
of the arterial wall in sclerosis is compensated by an
enlarged diameter in such a way that hemodynamically they are behaving almost identically.
In the Research instrument it is also possible to enter these patient data at a later time while doing the
measurement, but this means that if stroke volume
and cardiac output are needed they must be recomputed, with the correct patient data for the entire
file, in off--line analysis using the original pressure
waveforms. The Beatscope software alerts the user
to this situation and will perform this analysis when
so instructed.
6.7 Setting a subject’s data
6.7.1 Thermodilution cal
To set any of the values gender, age, height or weight:
1.
2.
3.
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4.
5.
6.
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press / or . to move to the desired parameter
and column on the tab card,
press 4 or 5 to change the value of the parameter,
press / or . to move to the other parameters
and change their values,
note that in the right model information panel
the entries Pat: BSA: have not yet changed.
press the [Describe subject] button just below
the screen to enter the data,
check that the entries Pat: and BSA: did
change.
The fifth parameter that can be adjusted on this tab
card is Calib-%. Entering gender and age sets the
aortic cross--sectional area, A, to an average value for
the population of that age and gender, with fine adjustments for height and weight possible. In contrast
to the other aorta parameters, the ‘A‘-parameter has
a rather poor precision of somewhat less than 20%.
Unfortunately, the absolute level of the stroke volume
and cardiac output computed is directly proportional
to A. A 10% wider aorta than the population means
a 10% greater cardiac output for the same pressure
level and waveform. The ‘A’-factor should be calibrated out, but this requires an extra measurement,
for example by thermodilution or US Doppler aortic
diameter.
If, during a measurement, a thermodilution cardiac
output estimate is 4.5 l/min and Modelflow indicates
5.0 l/min, then set Calib-% to: (4.5/5.0) × 100 =
90%.
1.
2.
3.
press / or . to move to the Calib-% column
on the tab card,
press 5 several times to change the value from
100 to 90,
accept the changed value by pressing [Describe
subject].
6.7.2 Aortic diameter cal
If an US scan measures a thoracic aortic diameter at
the current pressure of 29.3 mm, but in the left model
information panel the diameter shown is 25.4 mm,
then:
1.
2.
3.
press / or . to move to the Calib-% column
on the tab card,
press 4 or 5 until Dao: shows the same value,
accept the changed value by pressing [Describe
subject].
6.8 The pressure--volume diagrams
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The small diagrams shown on the {Describe subject}
card at the far right serve to show the importance
of entering proper age and gender. The resultant
aortic pressure--volume diagram is shown in black
and the associated pressure--compliance diagram in
purple color. Pressure ticks on the horizontal axis
are at 50 mmHg increments; pressure span is 0 to
200 mmHg. Both curves are clearly nonlinear. The
compliance curve for the young adult is rather wide,
peaks at 50 mmHg to decline moderately at higher pressures. For the elderly subject the compliance
peaks at 10 mmHg, peaks higher, and decreases more
quickly with increasing pressure.
The importance of this nonlinearity can perhaps best
be clarified with a numerical example. Given aortic
compliance we can compute the volume pressed into
the aorta by measuring its associated pressure rise. If
this compliance is 2 ml per 1 mmHg pressure increment then a pressure rise of 40 mmHg during the systolic pressure upstroke means a stroke volume of 40
× 2 is 80 ml. The aorta’s compliance at low distending pressure is, as indeed shown, substantial but at
higher distending pressures compliance progressively
decreases. Typically, for a 50 year old patient aortic
compliance could be 3 at 50 mmHg distending pressure, 1.1 at 100 mmHg and 0.5 at 150 mmHg. Thus
the same 40 mmHg pulse pressure equates to 120,
44 and 20 ml stroke volume depending on pressure.
Moreover, the numbers change with the patient’s age
and nonlinearity is more severe in the elderly. Aortic
compliance is no solid physiological basis for a pulse
contour method unless carefully modelled. 16
6.9 The Select trends card
The fundamental Finometer signal is pressure. It is
always displayed in the lower trend panel and cannot be deselected. On display are the pressure pulsation left, the systolic, diastolic, and mean level trends
at selectable sensitivity, and S/D numerically in selectable units (mmHg, hPa or kPa). The vertical
scale for the pulse display and for trending are always
the same, see facing page top diagram. Depending on
configuration (see section 7.6 on page 72) direct
finger arterial pressure or a processed, reconstructed
pressure pulse are displayed. This is indicated above
the pressure trend panel. Default it is Brachial
from FIN before RTF-cal initially. The currently
configured unit of measurement is also shown, here
the mmHg.
and 8 h full scale. Only the most recent period data
are shown. Thus, when viewing the past it appears
as increasingly compressed with further averaging applied. To select a time scale:
The relationships between the selection columns on
the {Select trends} card and the derived parameter
and display scales is shown on the facing page. To
select any parameter or scale:
index
Any two of fifteen available parameters can be selected for trending in the upper trend panel. All are
derived from pressure: MAP, CO, SV, TPR, HR, IBI,
LVET, D/SPTI, PS*HR, CI, SVI, PRI, dp/dt, Zao,
Cwk. Trends and numeric displays show 8--beat running average values. The numeric values are updated
in pairs once every other second. Their meaning and
computation details are described in section 3.5 on
page 31.
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There are four time scales: spanning 6 and 30 min, 2
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1.
2.
3.
Press the [Select trends] button once.
Press . until the Time scale select column is
highlighted.
Press 4 or 5 until the desired time scale is
displayed. The selection effect is immediate.
The time span displayed offers the most recent window on a possibly larger recording. The displayed
period since measurement start is shown below the
time axis in both trend panels.
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1.
2.
3.
Press the [Select trends] button once.
Press / or . until the desired select column is
highlighted.
Press 4 or 5 until the desired parameter or
display scale is shown. The selection effect is
immediate.
6.10 Cardiac oxygen supply/demand
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The build-up of tension in muscle is associated with
great oxygen consumption. The shortening of muscle
and ejection of blood consumes much less. Thus, the
height of the generated systolic pressure points to the
level of cardiac oxygen demand per beat. The higher
the heart rate is, the more often this amount of oxygen is demanded per minute. Thus, PS*HR is considered an index for cardiac oxygen demand per min.
Finometer computes this index for display, trending
and output.
principally proportional to systolic pressure maintained in systole (systolic pressure time index) on the
other, their ratio (DPTI/SPTI) is considered an index of cardiac oxygen supply/demand. This index we
labeled D/SPTI, expressed in %. Levels below 50%
are often associated with ST-segment depression. For
the computation of D/SPTI in Finometer a reconstructed aortic pressure waveform is used obtained
by inverse filtering, and independent of the choice of
pressure reconstruction that is made.
The product of systolic pressure and heart rate is expressed in meters--mercury--per--minute and selected
as the right trended parameter, facing page. The
unit of m Hg/min is equivalent to k--mmHg/min, thus
7.57 m Hg/min as displayed means 7570 mmHg/min.
Inverse filtering is the process whereby a waveform
passing by in real time is subjected to an inverse
transfer function. The effect is the same as applying an inverse transfer function in off--line computer
analysis but is achieved in a different way. The inverse finger to aorta transfer function in Finometer is
experimental in that it is obtained over a somewhat
smaller population than usual. Its shape, however, is
essentially identical to ones published in literature.
With the perfusion of cardiac muscle mainly taking
place in diastole and being proportional to diastolic
pressure (diastolic pressure time index) on the one
hand, and cardiac effort and hence oxygen demand
6.11 The Select A/D signal card
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The waveform display in the signal information panel is like an oscilloscope. It displays one of the four
Finometer original signals as in the table below, or
external signals when they are connected and chosen for sampling. At the same time these signals are
stored in the packet files and output via the analog
I/O box. For the oscilloscope, the channel, its vertical sensitivity, zero line position and time scale can
be selected. The left vertical scale shows which internal signal or external channel number is viewed.
Thus the oscilloscope display, the analog output signal, and the packet stored signal are identical.
beled Ext 1..4. Each pixel represents several samples. All samples are taken and a vertical line is
drawn between the minimum and the maximum value. Thus no fast oscillations are missed.
To display a channel:
1.
2.
3.
4.
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Channel
Label
Signal
1
2
3
4
FinAP
Height
Armcuf
Pleth
Finger pressure
Finger hydrostatic height
Arm cuff pressure
Finger plethysmogram
Table 6.1
5.
6.
7.
Press the [Select A/D signal] button.
Press / to highlight the Channel select column.
Press 4 or 5 to select one of the channels
[1..4]. Note that it is possible to select dsp off
in which case the display area is blanked.
Press . to reach time axis setup column T
[s/div]. The fastest speed is 0.5 s/div. A division is marked with a black dot and is about
1 cm wide.
Press . to set the position of the zero. Three
choices are: at top, middle, bottom.
Press . to set full scale (FS) sensitivity.
The effect of all selections can be seen immediately.
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Note that the reconstructed brachial artery pressure
(reBAP) is not shown here, is not stored in the packets, and is not available as an analog output. reBAP
is reconstructed later in Beatscope from FinAP with
the same algorithms as are used in Finometer.
When an external analog signal is selected it is preprocessed for offset and sensitivity, displayed, and la-
A typical setting for the channel 1 display (FinAP)
to judge waveform quality is:
•
•
•
•
channel = 1
time scale = 1 s/div
Zero at bottom
FS = 2.5 V ≡ 250 mmHg
6.12 The Physiocal card
This tab card has a left or Physiocal--side, a middle diagram panel used by both sides, and a right or
RTF--cal--side. Emphasized here (facing page) is the
Physiocal side. It shows that Physiocal was turned
off possibly to perform a Valsalva maneuver without
having it interrupted by a Physiocal. The off state is
also shown top right in the Finometer display:
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Physiocal off ! Physiocal is normally on. When
Physiocal remains off for more than a few minutes
the top right display will flash reminding you.
•
•
•
To switch Physiocal states:
1.
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From its present state press 4 or 5 or press the
[Physiocal & RTF-cal] button. Either action
switches state.
Press any one of these buttons again and switch
Physiocal state once more, and so forth.
From any situation in the Finometer--research
instrument press the [Physiocal & RTF-cal]
button once to select it and once more to switch
Physiocal states.
The Physiocal side presents Physiocal diagnostics information:
•
Physiocal excellent. This is the best grade
•
•
•
available. The other levels are great, good, useful, sufficient, adequate, inadequate, very
inadeq, uncertain.
setp 334 indicates a good size finger on which
measurements are made easily. But any servo
setpoint level is in principle acceptable.
pleth 90 indicates a good size artery on which
measurements are made easily. This number
may be seen to vary from 4 to 400 between subjects. The larger the better.
gain 106 indicates a well performing servo loop.
Gain preferably is some 20 to 50% greater than
pleth. If much greater then an oscillation may
have occurred on which the servo system automatically reduces gain, which results in a larger
gain number.
shape 4 indicates well formed plethysmograms.
Values may range from 0 to 16. Lower values are
better.
state LOG indicates the state of the adaptive
servo control system. Possibilities are L/S, O/F,
G/Q.
The dual diagram in the middle panel shows the
finger arteries pressure--volume curve in black
and a Marey oscillogram in blue. The horizontal scale has 100 mmHg tick marks, the vertical
scale is arbitrary.
6.13 The Return--to--flow--cal card
That no RTF has been done yet can be seen just
above the pressure trend panel where is written Brachial from FIN before RTF-cal. To perform a return--to--flow systolic calibration take the following
steps:
1.
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2.
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3.
4.
5.
Wrap the upper arm cuff provided with your Finometer (it should have two air hoses) tightly on
the arm where finger pressure is measured. Return--to--flow will be detected automatically by
the finger cuff.
Insert the tube sockets into the Finometer front
side, either way is right, see figure 4.6 on
page 40.
Press the [Physiocal &RTF-cal] button.
Press . to activate the RTF--cal side.
Press 5 to select a cuff inflation type. A step
inflation is often found more pleasant since it is
quick and reduces congestion distal of the upper
arm cuff. In about 50% of the subjects pooling
is so small that finger pressure after stepwise inflation drops to values too low to be measured
with Finometer. In such cases select a
ramp
inflation, and/or hold the hand below heart level.
6. Wait at least two minutes since the previous
RTF--cal. This can be monitored on the tab card
as Ago 10 min
7. During the 30 s before inflation starts ask the
patient to be quiet, without movement or talking.
8. Press the [Physiocal &RTF-cal] button. This
starts inflation. Inflation is smooth and deflation linear. To emergency--stop press this button
again.
9. While deflation progresses observe the middle
panel. A first RTF level is detected after which
a reinflate takes place. Both RTF levels detected
are displayed in yellow.
10. Upon successful completion the RTF and Tot =
RTF + cor level shifts will be computed and updated. Positive values mean up--shifts of finger
pressure.
6.14 The Derived variables card
The {Derived variables} card replaces the {Configure}
card during a measurement run. On this card there is
nothing to control or adjust. Configuration of options
is not possible during a run.
On the {Derived variables} card 12 variables are displayed numerically, lined up in four columns, from
the left:
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1.
2.
3.
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4.
pressure levels derived from the processed waveform,
time intervals derived from the unprocessed
waveform,
flow related values derived from the computed
flow waveform,
flow related values indexed for body surface area
(BSA) according to Dubois and Dubois.
All values are 8--beat running averages updated ev-
ery 1 s. The units are added, and depend on the
unit system originally configured. The colors of the
values correspond to the trend colors. In fact, all
derived variables colors are fixed and the same and
coordinated throughout the displays, (appendix C
on page 116). The symbols indicating the variables
are shortened to 2 characters due to lack of space.
Some unusual ones: PI is pulse interval (IBI), ET is
left ventricular ejection time (LVET), RI is peripheral
resistance index (PRI). The big white arrows indicate
corresponding parameters. The values are not identical at all times since the big numbers displays are
updated less frequently.
These are 12 parameters, selected from the pool of
beat--to--beat derived variables available and considered most useful for normal monitoring. More exotic
ones can be displayed with the {Select trends} card,
see page 59.
7 Configuring the Research instrument
The {Configure} card is only available off--line and used to check the calibration of pressure transducers,
and to set various process parameters in order to adapt to various tasks and situations. The possibilities are
grouped into five sections:
u
t
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u
t
u
t
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t
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t
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transducer check: The Finometer has pressure transducers whose zeroing is automatic but whose
sensitivities need to be checked. Erroneous sensitivities cannot be adjusted in the field. These four
sensitivities can be checked:
1. the upper arm air supply buffer can be checked to reach the appropriate level;
2. the hydrostatic height sensor zero and sensitivity can be checked and the zero offset can be nulled;
3. the finger cuff pressure transducer can be checked for sensitivity and linearity against a calibrating
manometer;
4. the arm cuff pressure transducer can be checked similarly.
pressure reconst: Pressure reconstruction is the conversion from finger pressure to brachial artery
pressure. Its details can be chosen under Configure.
external signals: Finometer allows the sampling of external analog signals to be stored simultaneously with finger pressure. In addition, finger pressure itself can be replaced by an external analog
pressure signal, optionally recorded at another anatomical site.
date and time: For accurate event recording all clocks should be synchronized. Finometer clock date
and time can be set under Configure.
miscellaneous: Five personal, color coded Finometer configurations can be stored and recalled; finger
switching intervals can be set (not in the present nullseries); the internal beeper can be turned off or on;
the system of display units (mmHg, hPa, or kPa) can be chosen.
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7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
Transducer check—buffer pressure
67
Transducer check—height nulling
68
Transducer check—height calibration
69
Transducer check—finger cuff
70
Transducer check—arm cuff
71
Pressure reconstruction
72
External signal input
73
Which channel to choose?
74
Setting date and time
75
7.10
7.11
7.12
7.13
7.14
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Miscellaneous—finger switching
76
Miscellaneous—display units selection
Miscellaneous—the beeper
78
Miscellaneous—saving a configuration
Miscellaneous—loading a configuration
77
79
80
7.1 Transducer check—buffer pressure
To check arm cuff buffer pressure:
1.
2.
3.
4.
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5.
6.
If not already done, switch Finometer on.
Select and start the Finometer--research instrument.
Press the [Configure] button once to select it.
Press 4 or 5 to highlight section transducer check
Press / to reach the Select xdcr column.
Press 4 or 5 to highlight Buffer. The display on the facing page should now show.
A simulated mercury column indicates arm cuff air
buffer pressure. In rest, buffer pressure cycles between 750 and 800 mmHg by automatic switching of
the air pump. This can be heard. A pump on/off
cycle should be nearly 1 min. If the pump cycle is
much shorter an air leak may be present.
The upper arm cuff is inflated from this air buffer.
This allow a smooth and controlled, almost pleasant
inflation. Although buffer pressure is higher, actual
arm cuff pressure is limited to 300 mmHg, both by
a hardware circuit and a software guard. In the case
that a higher arm cuff pressure is reached circuitry
tries to reduce arm cuff pressure to zero immediately
and to switch off the pump. When this process is
insufficiently effective, or when the procedure takes
too much time (in compliance with CEI IEC 601-2--30) a visual warning is displayed, accompanied by
30 beeps. In that case you are to remove the upper
arm cuff at once.
7.2 Transducer check—height nulling
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In the white field at the left the current height difference value is displayed in cm. On the left information
panel Hite: is also shown in mmHg. Both indicate
0. Note the blue text on the card, explaining what to
do to zero the system and to check its sensitivity.
The more involved way is by using the {Configure}
card:
Height correction nulling is normally automatic from
the stored value of a previous run. It is only when the
frontend or height system became disconnected that a
manual re-null is required. Nulling can be carried out
only when Finometer does not measure finger pressure. Nulling can be done in two ways. The quick
way is to hold both sensors together (as shown in
section 4.4 on page 39) and press the mark button.
3.
4.
1.
2.
5.
Press 4 or 5 to highlight Height. The display on the facing page should now show.
Hold both sensors together (see section 4.4 on
page 39) and press the [Configure] button.
Height should now read 0 cm.
7.3 Transducer check—height calibration
To check the height sensor system sensitivity:
mm.
1.
2.
If the sensors are held 100 cm apart vertically, and
the indicated height is only 90 cm, the system has
a 10% error. This unit should be replaced. There
are no field serviceable parts here. In the case that
no immediate replacement is available, it is best to
keep the hand close — within 20 cm — to heart level. In that case a hydrostatic height difference of no
greater than 20 cm is associated with an error of less
than 2 cm (10% of 20 cm) blood column or 1.5 mmHg
in blood pressure for the defective unit, which is often acceptable, and 90% of the height error is still
corrected.
3.
4.
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5.
6.
7.
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Press 4 or 5 to highlight Height. The display on the facing page should now show.
Hold both sensors together (see figure 4.5 on
page 39) and verify that height reads 0 cm.
Hold both sensors 50 or 100 cm or any known
vertical distance apart, and verify that the
Height indicator reads the same distance.
In the left information display, for a 50 cm distance, Hite: should indicate −50 × 0.78 which
is −39 mmHg.
The factor 0.78 arises from the density ratios of blood
(ρ = 1.06) and mercury (ρ = 13.6), adjusted for the
fact that one column is measured in cm, the other in
The height correction system removes the hydrostatic
errors that are caused by small shifts in finger position that otherwise go unnoticed. Since a 1.3 cm shift
in finger height already causes and error of 1 mmHg
the importance of this system is clear.
7.4 Transducer check—finger cuff
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The Finometer generates setable air pressure at the
frontend box so you don’t need another source of air
pressure:
10. Linearity can be checked by measuring at each
50 mmHg level increment up to 250 mmHg maximal pressure.
1.
2.
When Finometer is set to generate a certain pressure, such as 100 mmHg, its built--in servo system
attempts to reach that pressure. This attempt will
be unsuccessful when there is a leak in the system
and Finometer indicated pressure will then be less
than the set level. If, in an airtight system, the
calibrating manometer and the Finometer indicated
pressures differ by more than 3 mmHg then either one
or both transducers have a sensitivity error. If you are
certain of your own calibrating manometer then the
Finometer transducer requires servicing. This cannot be done in the field and the frontend has to be
returned to FMS, Finapres Medical Systems BV (see
page 3). If, however, your calibrating manometer
also has a 1% error the errors of both transducers
add and you should allow for a 6 mmHg difference
between the two.
3.
4.
5.
6.
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7.
8.
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Press 4 or 5 to highlight Finger.
Press / to reach the setable air pressure column
equipped with the simulated mercury column.
The display on the facing page top panel should
now show, but with null selected.
Verify that the numeric display shows Finger 0
mmHg. This nulling is automatic. If a 0 is not
shown there may a fault in the system.
Insert a Luer into the frontend air outlet and run
an air hose to your calibrating manometer.
Press 4 twice to set a 100 mmHg air pressure,
indicated as Finger 100 mmHg, see facing page
bottom panel. If a lower pressure is shown there
may be a leakage in the air system just connected.
Check that your calibrating manometer also indicates 100 mmHg or its equivalent 133 hPa,
or 13.3 kPa. Differences should be less than
3 mmHg or 4 hPa or 0.4 kPa.
Handle transducers carefully, do not expose to extreme pressures or drop tests and mechanical shocks.
With some care solid state transducers keep their calibration for the life of the device.
7.5 Transducer check—arm cuff
The arm cuff transducer is located in the main instrument behind the air hose receptacle marked ‘s’
in figure 4.6 on page 40, bottom left.
1.
2.
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3.
4.
5.
6.
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7.
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8.
Press 4 or 5 to highlight Armcuf.
Press / to reach the setable air pressure subsection with the simulated mercury column. The
display on the facing page top panel should now
show, except with null selected.
Get the air hose and connector assembly shown
in the facing page upper panel.
Insert the Luer into the frontend air outlet and
the other side into the main instrument receptacle marked ‘s’, front side, bottom left.
Verify that the numeric displays show Finger 0
mmHg and Armcuf 0 mmHg. This nulling is auto-
matic. If a 0 is not shown there may a fault in
the system.
9. Press 4 four times to set a 200 mmHg air pressure, indicated as Finger 200 mmHg, see facing
page bottom panel. If a lower pressure is shown
there may be a leakage in the air system just
connected.
10. Check that the Armcuff transducer also indicates 200 mmHg. Differences should be less than
6 mmHg since each transducer may have a 1%
of 300 mmHg full scale error.
The arm cuff pressure transducer can also be
checked with the Finometer--classico instrument, see
section 9.2 on page 94. This is theoretically a better way since the transducer is then checked directly
against your calibrating manometer and not indirectly against the finger pressure transducer.
This concludes the section on transducer check.
7.6 Pressure reconstruction
The Finometer--research device allows to select the
details of finger--to--brachial waveform reconstruction
as follows:
1.
2.
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3.
4.
5.
6.
7.
Press 4 or 5 to highlight section pressure
reconst
Press / twice to reach the Filter column.
Press 4 or 5 to highlight
to brachial.
This is also the default setting.
Press / and 5 to reach the Level cor column
and select yes.
Press / and 5 to reach the Level CAL column
and select yes.
Press the [Configure] button to confirm.
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You have now set Finometer to what is already its default: full reconstruction. You may select any combination of filtering and level correction and calibration,
but to level correct filtering must be selected:
1.
Press
. twice to reach the Filter column.
2.
3.
do not, see figure top
Press 4 to highlight
panel.
Press the [Configure] button to confirm.
You have now set Finometer to no reconstruction at
all. Finger arterial pressure will then be displayed
as with a Finapres device, see figure bottom panel. Without finger--to--brachial waveform filtering no
level correction or calibration is defined.
The four reconstruction options are:
1.
2.
3.
4.
Waveform filtering to brachial artery pulsations
only. 6
Waveform filtering plus level correction. 7
Waveform filtering plus level calibration. 2
Full brachial artery pressure reconstruction. Full
reconstruction includes the generalized waveform filter, the generalized level correction and
a further individual level calibration from a return--to--flow systolic determination added.
7.7 External signal input
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Finometer--research normally records four internal
analog signal but each one can be replaced with an
external signal. Channels 2, 3 and 4 can sample any
signal (always at 200 Hz sample rate). When channel 1 is configured “external” the normal Finometer
finger pressure measurement cannot be started. Instead the external signal is analyzed after pressing
start/stop . It must be an arterial pressure waveform
of proper calibration:
1.
2.
3.
4.
5.
6.
Connect the external pressure signal to the
analog I/O box input--1 BNC connector, see
figure 2.2 on page 20 and section 2.4 on
page 23 for instructions.
Press 4 or 5 to highlight section external
signals
Press / to reach the Channel-nr column.
Press 4 or 5 to highlight 1=pressure.
Press / and 5 to select external. The message
Set pressure reconstruction...
7.
8.
9.
10.
11.
12.
13.
is displayed, see facing page top panel. Defer this
to last.
Apply a zero pressure signal to input--1. If the
Source-mV voltmeter does not read 0 then:
Press / to reach the Offset-mV column.
Press 4 or 5 until the Source-mV reads 0, facing page, bottom panel. A 1 mmHg offset shows
up as 10 mV.
Next, apply a known fixed pressure to input-1, say 100 mmHg. The Source-mV voltmeter
should now indicate 1000 mV, see figure 7.9
upper panel. The Source-mV shows 1033 mV,
however, which is interpreted by Finometer as
103.25 mmHg, an error of +3.25%.
Press / to reach the Sensitivity- 0/00 column.
Press 5 until the Source-mV reads 1000, see
figure 7.9 lower panel. The channel is now
ready for recording.
Move to pressure reconst to set the anatomical recording site and the required pressure reconstruction, section 7.6 on page 72.
7.8 Which channel to choose?
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To Finometer--research you may connect up to four
(4) external signals for input, sampling and simultaneous internal storage in the packet file. Except for
input--1 which is always treated as a pressure signal,
these channels are not analyzed, they are just recorded. Think of ECG leads, 2 respiratory signals, tilt
table tilt angle, rectified MSNA recordings or rectified EMG, Doppler flow velocity, ergometer exertion
level, an analog marker signal, etc. The sample rate
is 200 Hz. The input voltage range is from −5.12 to
+5.12 V with a resolution of 2.5 mV. Milli--volt amplitude signals, therefore, should be amplified first.
Each one of the following four Finometer internal signals normally stored can be replaced with an external
analog signal.
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Channel
Label
Signal
next page
1
2
3
4
FinAP
Height
Armcuf
Pleth
Finger pressure
Finger hydrostatic height
Arm cuff pressure
Finger plethysmogram
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Table 7.1
index
Consider which of these internal signals to best omit.
Normally one would be least interested in the plethysmographic signal of channel 4 since it is near zero
most of the time, then least in the only sporadically (during a return--to--flow calibration) nonzero arm
cuff pressure signal of channel 3, then least in the
height signal of channel 2 whose value is already used
internally to correct the finger pressure for hydrostatic level errors. Replacing the finger pressure signal of
channel 1 with an external signal, however, results in
pulse feature detection and Modelflow cardiac output computation being performed on the externally
provided pressure waveform.
Even though, for example, the arm cuff pressure is replaced by an external signal, Finometer still has the
arm cuff pressure signal available internally and will
read its value at the instants of return--to--flow systolic detection as usual. In other words, the normal
functioning of Finometer--research is not affected by
configuring the signal channels 2 to 4 externally, as
long as channel 1 is configured as internal.
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2
An ECG sampled at 200 Hz is undersampled for fine diagnostic purposes. For heart rate variability computations 200 Hz suffices
if (parabolic) interpolation is used to refine the R wave fiducial point (see page 359 of 19).
7.9 Setting date and time
To set the date and time:
1.
2.
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3.
4.
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5.
6.
Press 5 or 4 to highlight section date and
time. In six columns from left to right the current date and time are shown updated each second, facing page.
Press / thrice to reach the Hour column.
Press 4 once to change 16 to 17 h going from
summer (daylight saving time) to winter (standard) time.
Press / or . to move to another column.
Press 4 or 5 to change its value. Changes
take effect immediately and are reflected in the
on screen date and time displays.
as follows:
year mo da hh mm ss
2000 10 22 16 44 33
0OC22P16.445
Of the year only the last digit is used (0); the month
is translated to a two character mnemonic: (JA FE
MR AP MY JN JL AU SE OC NO DE); the date is taken in full; next follows a unique file type identifying
character, which is a P for a Finometer packet file;
this character is followed by the hour; the first two
digits of the extension is the minute; the last digit is
seconds divided by 6. Note that 33 divided by 6 is 5,
and seconds 30 to 35 also produce a 5.
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Date and time are used internally in the Finometer
software as a file signature. For this purpose the date
and time at the start of a measurement are taken
and combined into a signature string which is stored
in each packet of a file on disk. Further, date and
time are used to construct an 11 character file name
When off--line downloading a file with Finolink you
are thus able to see on which date and time a file was
generated. Finolink also shows the patient description to more easily recognize a patient file from the
directory listing.
7.10 Miscellaneous—finger switching
In the present Finometer devices switching between
cuffs is not available. In the software it has, however,
been prepared:
1.
2.
3.
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4.
5.
6.
7.
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8.
9.
miscelPress 4 or 5 to highlight section
laneous.
Press / five times to reach the Switching column.
Press 4 or 5 to highlight off.
Press the [Configure] button to activate. Finger switching is now inactive.
Press 4 or 5 to highlight 60 min, see facing
page.
Press the [Configure] button to activate. Finger switching will now occur every 60 min.
Press 4 or 5 to highlight now.
Press the [Configure] button to activate. Finger switching will immediately occur to move
monitoring to the other finger. Can be used to
test the proper functioning of finger switching.
Automatically timed finger switching can be suppressed in the 10 s just before the actual switch instant by pressing mark . A warning message and beep
alert the operator to a coming switch. After a period of uninterrupted monitoring on the same finger of
1 h the Cuff: message will change from dark gray
to orange color. After 12 h of uninterrupted monitoring Finometer will stop the measurement and this
cannot be prevented by the operator. Twelve hours
of monitoring on a single finger has not been seen to
do harm. 18
Frontend cuff switching may reduce irritation at the
finger in awake patients, see a note on cyanotic finger
tips in (section 4.3.4 on page 38).
Pressures may differ between fingers. 11
7.11 Miscellaneous—display units selection
The Finometer--research instrument can display its
results in two unit systems: a “medical” unit system
(MU) and the “SI” unit system. In the SI unit system
pressures can be displayed as hPa or kPa:
1.
2.
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3.
4.
5.
laneous.
Press / four times to reach the Display column.
Press 4 or 5 to highlight hPa (SI). The display changes immediately according to the new
choice, see facing page.
mmHg (MU), to
restore the default unit.
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The world wide measurement unit system since 1960
is the Système International d’Unités or SI system. In
this system the mmHg was accepted only temporarily. Thus the official unit of pressure since 1960 is the
pascal (Pa). The conversion factor from mmHg to
pascal is 133.3224 or very nearly 400/3 and to hectopascal (hPa) it is nearly 4/3. Finometer internally
uses the mmHg. The factor of 400/3 is used for conversion to pascal units.
The m` for volume and acronym units such as lpm
and bpm are used in both systems without change.
The total peripheral resistance (TPR or SVR or Rp )
of a patient is a quantity that cannot be measured
directly but is derived from the simultaneous measurement of pressure (p) and flow (q) by division:
Rp = p/q. In medical units pressure is expressed
as mmHg and flow as m`/s. Thus the medical unit
for Rp is mmHg.s/m`. On the display and in the
output results file pressure is in mmHg and cardiac
output in `/min. Peripheral resistance, however, is
often expressed in CGS (the now obsolete centimetergram-second system) units. In this system pressure
is expressed in dyn/cm2 and flow in cm3 /s, and consequently resistance in dyn.s/cm5 . To convert from
mmHg to dyn/cm2 use 4000/3. To convert from
`/min to cm3 /s use 1000/60. Thus, to compute Rp
from pressure and cardiac output divide the numbers
and multiply by 4000/3 × 60/1000 = 80. For example, mean arterial pressure is 100 mmHg and cardiac
output is 4 `/min. Resistance then is 100/4 × 80 =
2000 dyn.s/cm5 .
7.12 Miscellaneous—the beeper
Finometer has a built--in beeper which produces a
repetition of brief sounds at 2047 Hz for 80 ms. To
turn it off:
1.
2.
3.
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4.
laneous.
Press / three times to reach the Beeper column.
Press 4 or 5 to switch states on--off or off--on.
The resulting beeper state is also shown in the
left information display under Beep: off.
The beeper is used principally to alert the operator to
developing error states. Three beeps are then given.
Confirmation of certain selections is also associated
with beeps.
Typically the beeper would be turned off when the
operator is not in the same room, or during night
time monitoring, or when a subject should not be
distracted from his/her task.
7.13 Miscellaneous—saving a configuration
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Preparation of a configuration might typically involve
a physiologist with Finapres experience who wants
Finometer to mimic an Ohmeda 2300e Finapres, no
warning beeps, displays in SI and kPa, view trends
of heart rate and stroke volume, and to work with
young adults. He wants to save this configuration for
later use. He achieves this as follows:
7.
8.
9.
1.
12.
13.
2.
3.
4.
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5.
6.
Press the [Describe subjects] button once to
select it.
Press / or . several times to reach the Age
column and press 5 until 25 is shown.
Press the [Describe subjects] button once to
confirm.
Press the [Select trends] button and set the
Left signal to SV, stroke volume. Set the
Right signal to HR, heart rate.
Press the [Configure] button once to select.
Press 4 or 5 to highlight pressure reconst.
10.
11.
14.
15.
16.
17.
Press / twice to reach the Filter column.
Press 4 to highlight do not.
Press the [Configure] button to confirm. Selecting no filtering automatically disables Level
cor and Level CAL.
Press 4 or 5 to highlight miscellaneous.
Press / five times to reach the Switching column.
Press 4 or 5 to highlight off.
Press . once, then 5 twice to highlight kPa
(SI).
off for
Press . once, then 5 to highlight
the beeper.
Press . to reach the Safe config column.
Press 4 or 5 to highlight Blue.
Press the [Configure] button to activate and
to save all your settings and selections under the
Blue color.
7.14 Miscellaneous—loading a configuration
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On another day a Red configuration must be loaded:
5.
1.
2.
3.
4.
After a colored configuration has been loaded the
startup or ‘white’ configuration can only be restored
by exiting from and restarting Finometer--research.
Press the [Configure] button once to select.
Press 4 or 5 to highlight miscellaneous.
Press / once to reach the Load config column.
Press 4 or 5 until Red is highlighted.
Press the [Configure] button to load the Red
configuration.
8 The Finometer--clinique instrument
The principal objectives of the Finometer--clinique instrument are simplicity of control and operation, and
stability of display. Instrument control, therefore, is by six buttons below the display screen. Each button has
one function during off--line idling when no measurement is done and another function during a measurement.
During idling buttons are yellow colored and during a measurement they are blue colored for distinction.
Displays have fixed scales and present fixed signals.
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The essentials of Finometry, however, remain the same. Thus, the Clinique instrument has brachial artery
waveform reconstruction by default, and includes a return--to--flow calibration. Modelflow cardiac output is
computed for later analysis, but not displayed. Entering correct patient data, therefore, is again essential
since the SV/CO/TPR values and their correct trending depend critically on it. The Clinique instrument’s
first screen display (figure 8.2 on page 82) reminds the operator of this requirement by providing a series
of four buttons to enter patient data and by highlighting the second button from the left, labeled [Gender
[up]|[dn]]. Further buttons set [Age-y], [Height-cm], and [Weight-kg].
Finometer--clinique uses the same software procedures as Finometer--research. Thus it is guaranteed that the
same pressure waveform analysis generates the same beat--to--beat derived parameters with both instruments,
that the same error messages are generated, that the packet file is identical. On--line and off--line files
downloading are identical also. In contrast with the Research instrument, however, no remote control of the
Clinique instrument is possible. A measurement start/stop, Physiocal off/on, or a return--to--flow procedure
cannot be controlled from a remote PC, and external markers cannot be entered via the serial interface.
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
Entering patient data—clinique
82
The error message display—clinique
83
Files downloading from a remote PC
84
Show trends
85
The control buttons during off--line idling
86
Layout of the Clinique display
87
The control buttons during a measurement
88
Scale compression
89
Performing a return--to--flow calibration
90
8.1 Entering patient data—clinique
Enter the patient descriptive data before a measurement starts to get correct, scalable cardiac output
values and trending:
1.
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2.
3.
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4.
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5.
6.
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9.
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If not highlighted press the [Pat-f/m] button
once or use // or .. to move to this button.
Its current setting is shown just above the button
on screen in white on a dark gray background.
Here, facing page, it is decide.
Press 4 or 5 to change the setting of the parameter from decide to male or female. The
Pat: parameter in the right information is highlighted and the display changes in accord with
the changed setting.
Press the [Age-y] button or use .. to move to
this button.
Press 4 or 5 to change the value of the Age
parameter.
Press the [Height-cm] button once.
Press 4 or 5 to change the value of the Height
parameter.
Press the [Weight-kg] button once.
Press 4 or 5 to change the value of the Weight
parameter.
Check that the entries in the right information
display panel have obtained the correct value.
All four patient descriptive data have now been entered. Do this before a measurement starts since
these buttons are not available during a measurement.
Although cardiac output is computed it is not displayed. Thus, there is no need for and no way
to set cardiac output calibration in Finometer--clinique. But calibration can be linearly scaled in post-processing, without deteriorating tracking precision.
This is true only, however, when the patient descriptive data were set correctly.
For example, when during a head--up tilt uncalibrated Modelflow stroke volume drops from an initial 120
to 80 ml when tilted up, but a thermodilution estimate shows initial stroke volume to be 96 ml, the
scaling factor is 96/120=80%. After calibration the
initial Modelflow stroke volume of 96 ml now drops to
64 ml when tilted up. This drop is 33% in both cases.
The 33% is only correct if age and gender, height and
weight were set correctly.
8.2 The error message display—clinique
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Normally the top status line shows clock time and
time lapse since measurement start in green letters on
a black background. When an error occurs the time
display is replaced by an error message in red color. Typically, an error message signals a condition in
which Finometer cannot function properly and from
which it cannot recover automatically. The measurement is stopped and the error message is displayed
during 10 s. At the instant that the error occurs
3 beeps are heard, followed by another 3 beeps after
5 s. After another 5 s the message disappears and
another measurement start can be attempted.
In the case shown the finger cuff air hose got dislodged
and must be reinserted. After the forward slash (/),
the procedure that detected the error is named. The
error message is also stored in the last packet of this
measurement’s file on disk. Here are some of the error
messages that may show:
.
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Connect frontend/startAutolock
.
.
.
.
.
.
.
.
.
.
.
Check air supply/steadyPressure (facing page)
Check armcuff air supply/fillRivabuffer
Unstable pressure/steadyPressure
No plethysmogram/failAutolock
Finger too thin/checkFrontgainDn
Check cuff cable/centerPlet
Connect cuff cable/checkLEDcurrent
Faulty finger cuff/setLEDcurrent
cuff--LED problem/checkLEDcurrent
Error messages represent situations that are not considered dangerous. They have to do with dislodged
connectors, or with contracted finger arteries, or worn
cuffs. They do not represent alarm conditions such as
may be present when the hemodynamic parameters
of a patient move out of a preset safe range.
For a more complete list of error messages, causes
and possible actions see appendix B on page 114.
8.3 Files downloading from a remote PC
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made with the Finometer--clinique instrument is
stored in a revolving store on disk. In a full revolving store a newly arriving packet automatically overwrites the oldest packet present. A revolving store,
therefore, does not have to be erased. These files can
be downloaded off--line after the measurement by a
remote PC with program Finolink. Files downloading can also be done while the Finometer is doing
a measurement. This is called on--line downloading and regards only the currently generated file. For
on--line downloading you must start the Finolink program and click its “Monitor” button, see figure 2.4
on page 22. Finometer will allow this and cooperate
fully behind the screens, and without a distracting
message. It has no effect on the measurement.
To start either form of downloading:
Off--line files downloading was discussed briefly in
section 2.3 on page 22. In this case any measurement file in store can be selected for downloading.
This requires full control over the Finometer packet
store so that no new packets can be stored. Thus, off-line files downloading and doing a finger blood pressure measurement are mutually exclusive. A warning message is issued that a measurement cannot be
started, see facing page.
6.
1.
2.
3.
4.
5.
Get a “null-modem” cable. There is one supplied
with your Finometer.
Plug one end of the cable into the Finometer
serial I/O connector marked “RS232”, located
at the rear.
Plug the other end into one of the PC serial ports
possibly labelled COM1, etc. In the case that
the supplied cable is of insufficient length you
may extend it with ordinary (non--null--modem)
serial cable.
Start Finolink on the PC by double clicking on
its icon, or go via Beatscope.
If not yet done configure the COM port number:
click on ‘Configure’, the ‘Serial port’, and select
the desired COM port. Click on ‘Select’.
For on--line downloading click on “Monitor”. A
display is shown on the PC that is quite similar to the Finometer--research display. With the
Clinique instrument running on Finometer you
cannot remote control some of its functions as
was possible for the Research instrument, see
8.4 Show trends
When a measurement is finished the trend display
continues to be displayed for a brief period. After
this period a message is shown prominently “Start a
measurement”, to indicate that the device a ready for
another measurement, see figure 8.6 on page 86.
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The trend display just overwritten by this message,
however, is still available in the background. It is
recalled by pressing the [Show trends] button once
to highlight the button and a second time to activate.
8.5 The control buttons during off--line idling
When no measurement is in progress Finometer is
idling and called off--line. The on screen buttons
are colored yellow and the control buttons below the
screen from left to right have the following functions:
u
t
u
t
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t
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u
t
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t
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u
t
[Show trends] Press this button twice to redisplay the trend panel when it was replaced by
the message “Start a measurement”.
[Pat-f/m] Press to set a patient’s gender. This
is very important for cardiac output computation precision. When pressed a dark gray window is opened presenting the presently selected
gender. Press 4 or 5 to change the selection.
[Age-y] Press to set a patient’s age. This is
very important for cardiac output computation
precision. When pressed a dark gray window is
opened presenting the presently set age. Press
4 or 5 to change the age.
[Height-cm] Press to set a patient’s height.
This is important for cardiac output computation precision. When pressed a dark gray
window is opened presenting the presently set
height. Press 4 or 5 to change the height.
[Weight-kg] Press to set a patient’s weight.
This is important for cardiac output computation precision. When pressed a dark gray
window is opened presenting the presently set
weight. Press 4 or 5 to change the weight.
[use FinAP] Used to select either unprocessed
finger artery pressure (FinAP) or reconstructed
brachial artery pressure (reBAP) for display and
derived parameters computation. First the [use
FinAP] button is pressed to select it, then a second time to activate it. This causes the display
labeling to change. The button text changes to
[use reBAP]. Press once again to return to the
default reBAP based display.
The action of these buttons is immediate. No confirmation needs to be given. Once a measurement is
started by pressing the start/stop button these functions are no longer available and remain fixed during
the measurement.
The height system can be nulled when still off-line by following the instructions in section 4.4 and
figure 4.5.
8.6 Layout of the Clinique display
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The status line shows the TNO logo, the time display and a copyright note. During a measurement
the copyright note is replaced by the Physiocal state.
The time display left shows the system clock time
and right shows the time lapse since the start of the
current measurement or off--line idling period. The
system clock time can be adjusted in Finometer--research, see section 7.9 on page 75. When an error
occurs the time display is replaced by an error message.
BAP) waveform. The yellow trace is beat--to--beat
heart rate, except during a return--to--flow procedure
when it is replaced by arm cuff pressure. The vertical
scale is fixed and the same as that in the trend panel.
The time scale is nearly 100 s. With the [Hi speed
waveform] button the time axis is expanded 10× and
the waveform has the begin upstroke instants marked,
see figure 8.8 on page 88.
The information panel lists from the top:
The pressure parameter layer left panel shows
a trend display of the three pressure levels (S/D-M). The white dot is mean pressure. The blue dot is
heart rate. The vertical scale is fixed and the same for
all four derived parameters. The time scale is compressed automatically each time it reaches the end,
see figure 8.9 on page 89. The quadruple numeric display at the right shows from above the eight-beat running averaged systolic, diastolic and mean
levels and heart rate updated each second, computed on finger (FinAP) or reconstructed brachial artery
pressure (reBAP).
•
•
•
•
•
•
•
•
The waveform and information layer left panel shows the selected unprocessed finger (FinAP) or
processed reconstructed brachial artery pressure (re-
The program control buttons are treated in later
sections.
•
•
•
todays date (Date: Apr 06)
beeper on/off state (Beep: on)
present date/time filename (Filename:)
current file size (Size: 177 k)
patient gender and age (Pat: male 50)
patient height (H-cm: 175)
patient weight (W-kg: 75)
active cuff, minutes on this cuff and switch period (C2: 3/off)
finger hydrostatic height (Hite: -5 mmHg)
total level correction shift (Shft: 18 mmHg)
Physiocal quality factor (QF: great)
8.7 The control buttons during a measurement
When a measurement has begun the control buttons
below the screen have the functions shown just above
each button on the display screen. From left to right:
u
t
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u
t
t
u
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t
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[Stop plotting] Press this button to stop the
trend plot. The trend plot is halted although the
finger pressure measurement continues. The button text changes to: [Start plotting]. Press
again and the trend plot is cleared and a new
trend plot started. These actions have no effect
on the measurement, or on the result packet file,
which both continue normally.
[---] Not presently used.
[Hi speed waveform] Press this button to increase the plot speed of the waveform display.
The plot clears and starts at the left side at
a 10 times increased velocity, see facing page.
When reaching the right side, plotting returns
automatically to normal speed. Keep the button
depressed to continue high speed plotting.
[Turn off Physiocal] Press this button to
suppress the Physiocal procedure. This is then
marked in the status line upper right section.
The button text changes to [Turn on Physio-
u
t
u
t
cal]. Use this button to display uninterrupted
Valsalva and other short term maneuvers. Turn
Physiocal back on as soon as possible. Physiocal
should not be off for more than a few minutes
preferably.
[Start RTF calibrate] Press this button to
start a return--to--flow systolic calibration of reconstructed brachial artery pressure. The procedure is started and the button text changes to
[Stop RTF]. In the case that something is wrong
the procedure can be broken off by pressing the
button again. After a procedure completes another cannot be started until at least 2 min have
passed. During these two minutes the button
is blanked: [---]. A typical procedure is described in section 8.9 on page 90.
[Turn off beeper] Press this button to turn off
the beeper. The beeper is silenced and the button text changes to [Turn on beeper]. Press
again to turn the beeper back on. This is accompanied with a beep.
The action of these buttons is immediate. No confirmation needs to be given.
8.8 Scale compression
In the Finometer--clinique instrument vertical and
time scales cannot be freely chosen. The vertical
scales are fixed. The time scale of the waveform display is expanded by pressing the [Hi speed waveform] button.
The time scale of the trend display is compressed automatically as follows:
•
end of the display area is reached.
The clearing and compression cycle repeats with
30 min, 1 h, 2 h, etc. as full scale values.
The rationale is that a short experiment is shown at
maximal time resolution. A more extended test such
as a tilt table test which may last one hour is also
shown in full with its maximally possible resolution.
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After measurement start the display is cleared
and the time scale is set to run from 0 to 7.5 min
full scale.
Trend data is written every 1 s until the end of
the display area is reached.
Now the display is cleared and the time scale is
set from 0 to 15 min full scale.
The data already accumulated is averaged by
two and redisplayed, filling the display from 0
to 7.5 min.
The remaining space from 7.5 to 15 min is filled
with trend data written every 2 s, again until the
In case a series of short tests must all be displayed
at maximal resolution the plotting can be stopped by
pressing the [Stop plotting] button once to highlight and once more to activate. Press this button
now labeled [Start plotting] again and the display is cleared and started at highest resolution on a
time scale from 0 to 7.5 min.
This starting and stopping has no effect on the measurement, or on the result packet file, which both
continue normally.
8.9 Performing a return--to--flow calibration
The display, facing page, represents the state after
the return--to--flow calibration procedure took place.
To perform a return--to--flow systolic calibration take
the following steps:
1.
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4.
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7.
the arm where finger pressure is measured. Return--to--flow will be detected automatically by
the finger cuff.
page 40.
Wait until the [Start RTF calibrate] button
shows up.
During the 30 s before inflation starts ask the
patient to be quiet, without movement or talking.
Press the [Start RTF calibrate] button to
start inflation.
The waveform display is cleared and restarted.
During the RTF procedure beat--to--beat HR is
replaced by arm cuff pressure, initially in blue,
later in yellow color.
The ramp inflation is smooth and deflation lin-
ear. To emergency--stop press the [Stop RTF]
button as indicated in the waveform panel.
8. While deflation progresses observe the waveform
panel. A first RTF level is detected after which
a reinflation takes place for a second detection.
9. Upon successful completion the two RTF arm
cuff pressure levels detected are displayed as
RTF=success(144 & 134).
10. The level shift will be updated and displayed in
the information panel as Shft: 18 mmHg. Positive values mean up--shifts of finger pressure.
11. The [Start RTF calibrate] button is blanked.
To repeat the procedure wait at least 2 min until
the button reappears.
After a 5 s priming period at 20 mmHg, the Clinique instrument always does a ramp inflate and no
choice is offered. When the arm cuff pressure trace
turns yellow this indicates that the return--to--flow
detection is working. The two arm cuff pressure levels at which detection of return--to--flow took place
are stored in the packet file at their instants of detection. Any specific return--to--flow error messages are
displayed in the waveform panel, replacing the Press
[stop RTF] alert.
9 The Finometer--classico instrument
The Classico instrument uses part of the Finometer hardware to control upper arm cuff inflation and linear
deflation to the specifications as set up by the operator. When the cuff is inflated and deflated you do
your Korotkoff sound detection as usual and (mentally) record the associated cuff pressures. Cuff pressure is
displayed on a simulated mercury column and a digital readout is also available. When the mark button is
pressed the instantaneous cuff pressure is stored, or rather the value averaged over the 1 s before the marker.
Upon termination the list of marked values is displayed.
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Three forms of blood pressure reading are provided: the normal mercury sphygmomanometer type readout,
the blinded London School of Hygiene type readout, and the Hawksley Random Zero type readout.
For epidemiological purposes the London School of Hygiene sphygmomanometer was developed, featuring
blinded detection and cuff pressure storage at three phases of the Korotkoff sounds, followed by measured
readout on three mercury columns. This system is programmed in the Classico instrument. Press the mark
button at each detected phase and read pressure levels from a list displayed upon termination.
The LSH instrument was shown later to provide biased results for two reasons. First, the instrument read systematically low.
Second, it was thought that observers were late in pressing the buttons since there were no mercury column oscillations alerting
the observer. 5 Classico does not have the first error and tries to compensate for the second by recording the cuff pressure that
effectively existed 0.5 s earlier.
The successor of the LSH instrument was the Hawksley Random Zero sphygmomanometer. In this instrument
a random zero offset was created, to be subtracted later once the memorized pressures were noted down. This
system is also programmed in the Classico instrument. Zero offsets are chosen in the range from −15 to
+15 mmHg and, if the mark button is pressed at the Korotkoff detection instants, the offset cuff pressures
are recorded and automatically corrected upon display of the list of marked values. Thus no computations
need to be done.
The Hawksley Random Zero instrument had various subtle mechanical errors which rendered it inaccurate. 3 These are not present
in the Classico instrument due to its electronic nature.
The Classico instrument in its three modalities has, as yet, not been tested for bias and precision and should
not, therefore, be used for blood pressure epidemiology.
9.1
9.2
9.3
9.4
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Setting the in-/deflate and readout parameters
The Classico calibration waveform
94
The normal Riva--Rocci/Korotkoff measurement
The Classico random zero measurement
96
93
95
9.1 Setting the in-/deflate and readout parameters
The Classico instrument offers automatic fast inflation to a preset level, or slower manual inflation by
pressing the 4 button. There are a slow and a fast
linear deflation at setable rates. Finally, three types
of readout are offered: normal, random zero, and
blinded. All settings are stored and the next time
you start Classico it will preload your latest settings.
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1.
2.
3.
4.
5.
Press the [Setup inflate] button.
Press . to reach the Inflate column.
Press 4 or 5 to highlight to preset level.
Press / to reach the Preset level column.
Press 4 or 5 to increase or decrease the level
(range 20 to 300 mmHg).
Deflation: To set deflation:
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The fast deflate rate is often used after systole
has been detected. Keep 5 depressed during
deflation to activate.
Readout: To set a readout type:
1.
2.
Press the [Setup read] button.
Press 4 or 5 to highlight a readout type.
Inflation: To set inflation:
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6.
Press the [Setup deflate] button.
Press / to reach the Slow deflate rate column.
Press 4 or 5 to increase or decrease the rate
in mmHg/s (range 1.5 to 7.5 mmHg/s).
Press . to reach the Fast deflate rate column.
Press 4 or 5 to change that rate in mmHg/s
(range 5 to 20 mmHg/s).
The top status line presents clock time and time lapse
since start, and any error messages that occur. Below it, the summary panel shows the current settings
of the instrument. The narrow mercury column left
indicates the pressure in the air buffer. The mercury
column at the right shows arm cuff pressure. It has
a resolution of 1 mmHg, as does the digital readout.
Measurement results can be downloaded to a PC with
Finolink. Finometer must first be set to run the Finometer--classico instrument. Finolink then recognizes this instrument automatically. Once set up Finolink automatically requests and receives the results
of each new measurement. Results are fully documented with date and time, all the settings for that
measurement, and all marked arm cuff pressure levels. It is, therefore, necessary that you press the mark
button at the Korotkoff phases you detect. A total
of 10 markers can be stored per measurement.
9.2 The Classico calibration waveform
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The calibration waveform steps pressures up from a
50 mmHg initial level in 50 mmHg increments until the 250 mmHg level is reached, then switches
to 50 mmHg decrements until the 50 mmHg level
is again reached, then deflates. For patient safety
the calibration cycle does not automatically repeat.
At each level the pressure is maintained during 10 s.
With a calibrating manometer connected you may
verify Finometer--classico’s calibration.
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4.
5.
6.
7.
To calibrate:
1.
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3.
2.
Get several 50 cm long sections of 6×1 mm plastic tubing, a T or Y air hose connector, and two
Kuhnke sockets, see figure 7.6 on page 71, and
assemble.
Insert one Kuhnke socket in the arm cuff inflate
8.
9.
outlet marked “i”, see figure 4.6 on page 40.
Insert the other Kuhnke socket in the arm cuff
sense outlet marked “s”. These two steps connect the inflate and sense ports as would normally be achieved with a two-tubed arm cuff.
Connect the third air hose to your calibrating
manometer.
Press the [Setup inflate] button.
Press . to reach the Inflate column.
to calibration
levels.
Press the start/stop button.
Compare the pressure levels on screen with those
on your calibrating manometer. They should be
within ±3 mmHg. When the difference is greater
please contact FMS, see page 3.
9.3 The normal Riva--Rocci/Korotkoff measurement
The Classico normal RRK measurement includes controlled inflation and deflation of the arm cuff, optional mark button cuff pressure storage, and display of
a list of marked levels upon termination of the measurement. Up to ten instants can be stored.
To perform a measurement:
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either arm.
page 40.
Setup the various inflate, deflate and readout parameters according section 9.1 on page 93.
Note in the Summary panel that Inflate to
170 mmHg was chosen. This causes a step-wise
cuff inflation which is often found more pleasant
by the patient since it reduces distal venous congestion. Reduced congestion enhances Korotkoff
sound generation as well, and reduces effects of
an auscultatory gap.
Note in the Summary panel that slow deflation
has been set to 2 mmHg/s and fast deflation to
10 mmHg/s.
6. Note in the Summary panel and on the {Setup
read} card that Read column normally has
been chosen.
7. Press the start/stop button to start inflation. Inflation is smooth and deflation begun immediately. To emergency--stop and deflate press the
start/stop button again.
8. Optionally press the mark button at the instants
of detection of the various Korotkoff phases.
9. Press the start/stop button after the last Korotkoff sound was heard.
10. A list of maximally 10 cuff pressure levels is now
displayed, recorded just 0.5 s before the instants
when the mark button was pressed.
This finishes a normal auscultatory sphygmomanometric blood pressure measurement. The blinded
measurement runs identical except no display of arm
cuff pressure is shown and the sphygmomanometer
remains frozen. For blinded measurements you must
press the mark button to record the detection instants.
9.4 The Classico random zero measurement
The random zero measurement includes controlled inflation and deflation of the arm cuff, optional mark
button cuff pressure storage, and display of a list of
marked levels after termination of the measurement.
Up to ten instants can be stored.
To perform a measurement:
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either arm.
page 40.
Setup the various inflate, deflate and readout parameters according section 9.1 on page 93.
Note in the Summary panel that Inflate with
[up] key was chosen. This causes a smooth
ramp cuff inflation. Use palpation of the radial
pulse to determine the moment to stop inflation.
Note in the Summary panel that slow deflation
has been set to 2 mmHg/s and fast deflation to
15 mmHg/s.
Note in the Summary panel and on the {Setup
read} card that Read column random zero has
been chosen.
Press the start/stop button to start inflation. Inflation is first to 20 mmHg, then to 30 mmHg.
At that time the 4 button may be depressed to
increase cuff pressure. To emergency--stop and
rapidly deflate the cuff press the start/stop button again.
8. Automatic deflation begins immediately when
the 4 button is released. Press 4 again to
further inflate as needed.
9. While deflation progresses observe the simulated
mercury column and press the mark button at
selected Korotkoff phases.
10. Press the start/stop button after the last Korotkoff sound was heard.
11. A list of cuff pressure levels is now displayed
recorded at instants when the mark button was
pressed. These levels are already corrected for
random zero offset.
12. Assume you remember reading S/D as 147/85.
Now subtract 11 mmHg as instructed in the display. The result is 136/74. When you pressed
the mark button the instrument recorded 146/86
and duly subtracted 11 mmHg to display 135/75.
7.
This completes a random zero blood pressure measurement.
A Specifications
This device fulfills the provisions of the EC directive 93/42/EEC (Medical Device Directive), and the European
Standards EN 60601--1, EN 60601--1--1, and EN 60601--1--2.
0344
Manufacturer:
Simon Stevinweg 48
NL-6827 BT ARNHEM, The Netherlands
phone
fax
email
web
:
:
:
:
+31 26 3849080
+31 26 3849081
[email protected]
www.Finapres.com
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Important note: Specifications are subject to change without notice.
A.1
A.2
A.3
A.4
A.5
A.6
A.7
A.8
A.9
A.10
A.11
A.12
A.13
Unpacking—The Finometer components
Patient safety measures
100
Protective measures
101
Analog Input/Output
103
Environmental specifications
104
Electrical specifications
105
Mechanical specifications
106
Instrumental information
107
Instrumental accuracy
108
Connecting external equipment
109
Remote control
110
Safe data storage—Data durability
111
Unpacking—The data packets
112
99
A.14 Cleaning
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113
A.1 Unpacking—The Finometer components
Each Finometer consists of the units listed below:
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•
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Main unit.
A box holding the principle
electronic and pneumatic components, the embedded computer, the front panel control buttons (section 4.5), and the display. A three-pronged grounded power cord is included.
Frontend. A box to be worn on the back of the
hand or the wrist and containing connectors for
the finger cuff and the height correction system
(section 2.2).
Height system. A liquid filled tube with sensors at both ends measuring their relative vertical distance (section 4.4).
Analog Input/Output box. Eight BNC connectors provide for four--channel analog signal
input and output (section 2.1).
Six finger cuffs. Two each of three sizes of
finger cuff: white, S--size, small; beige, M--size,
medium; blue, L--size, large (section 4.1).
Arm cuff. A normal upper arm blood pressure
cuff with two air hoses to be wrapped around
the same arm as the finger cuff and used to accomplish the return--to--flow calibration of reconstructed brachial artery pressure.
Serial I/O cable.
A null modem cable to
connect Finometer to a remote PC’s COM port
for data downloading and remote control, using
Finolink software (section 2.3).
Calibrating air hose.
A length of 6 mm
•
•
•
•
outer diameter, 1 mm wall thickness plastic
tube equipped with Kuhnke socket and Luer
(figure 7.6), used to calibrate Finometer transducers.
Finolink.
A Windows software program to
download data from Finometer to a remote PC,
offering a remote monitor screen and some remote control of Finometer functions. Finolink
may unpack Finometer--type packed data files.
Finometer User’s Guide.
The document
you are presently reading.
FMS Finger Pressure Reference Guide. A
document containing background information on
finger arterial pressure measurement.
Beatscope. The Beatscope Windows software
program is present on CD-ROM to view waveforms and beat--to--beat derived data on a PC
screen.
The guides are available on CD-ROM as PDF files
in printable format and in interactive screen display
format. Use Acrobat version 4 or later for viewing.
Further copies are obtainable from FMS (page 3).
Upon unpacking a quick inspection of proper functioning is obtained by following the instructions
in chapter 2 on page 19. Transducer calibration
may be checked with the procedures described in
section 7.1 beginning on page 67. Please contact
FMS (page 3) immediately in case of malfunction.
A.2 Patient safety measures
•
•
•
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•
The data produced by Finometer or BeatScope
software is intended as an adjunct in patient assessment and should not be used as the sole means
for determining a patient’s diagnosis.
Finometer is a finger blood pressure monitor. Do
not use the finger cuffs on other members of the
body, such as a toe or the wrist of an infant. Performance on a toe is undocumented. Use on the
wrist of a neonate or small infant substantially reduces flow to the hand, causes venous congestion
and can be maintained only for very short periods
of not more than one (1) min.
Finometer can only be used on adult humans and
on children of 6 years or older. 14 Performance on
younger children is undocumented.
To maintain the designated operator and patient
•
•
•
•
safety only use accessories, such as finger and arm
cuffs, that are provided by FMS, Finapres Medical
Systems BV.
(U.S.A.) Federal law restricts this device to sale
by or on the order of a physician.
To maintain the designated operator and patient
safety, peripheral equipment that is connected to
Finometer or one of its components, must be certified according to EN 60601--1 for electromedical
equipment.
Use Finometer only with a properly grounded AC
power outlet.
Obey the voltage rating mentioned at the rear
panel near the line power connector.
A.3 Protective measures
Finometer electrical circuits do not touch the skin and are not in galvanic contact with body fluids. Finger cuff
pressure is zero during idling and not higher than intraarterial blood pressure during a measurement. Such
pressures can be tolerated for at least 12 hours of continuous monitoring. The highest pressure that can be
reached is 350 mmHg which is practically painless and does no harm but should not be applied continuously
for many hours. Still, further measures are taken for the safety and comfort of the monitored patient and for
the safety and convenience of the operator.
Electrical protective measures
•
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•
•
•
Low finger cuff LED voltage (approximately 1.4 V) and power dissipation (approximately 50 mW) reduce
electrical hazard and prevent undue heating which might cause skin irritation.
An electrical short circuit in the cuff or in the instrument cuts off cuff pressure within 1 s.
An interrupted frontend or cuff cable cuts off cuff pressure within 1 s.
A self test of essential instrumental functions and parameters is performed every second of time.
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Finger cuff pressure protective measures
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•
Compressed air fed to the Frontend unit is pressure regulated to 350 mmHg (0.5 bar).
A watch dog timer cuts off cuff pressure and resets the Finometer built--in computer and software in case
of internal computer malfunction.
A finger cuff pressure greater than 250 mmHg sustained for 2.5 s cuts off cuff pressure.
During the start procedure finger cuff pressure is limited to a maximum of 295 mmHg to last less than
2 s.
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•
An arm cuff pressure greater than 300 mmHg sustained for 5 s cuts off the cuff pressure pump and rapidly
•
•
deflates the arm cuff.
A return--to--flow procedure typically does not take more than 30 s, and cannot be repeated within 2 min.
During a return--to--flow procedure the arm cuff is fully deflated automatically if detection of return--to-flow fails within 1 min.
General system protective measures
•
•
•
•
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A watch dog timer cuts off cuff pressure and resets the Finometer built--in computer and software in case
of internal computer malfunction.
If finger cuff pressure oscillates during a measurement the software takes action to remove the oscillation,
although such oscillations present no hazard or discomfort to the patient.
When fully contracted finger arteries are detected during the start procedure, allowing no pressure monitoring, Finometer issues an error message to the display, and shuts off cuff pressure.
Increases in the contractional state of the finger arteries can be followed by inspection of the Physiocal and
servo control parameter display. A quality factor expresses from ‘excellent’, via ‘great’, ‘good’, ‘useful’,
‘sufficient’, and ‘adequate’, to ‘uncertain’ the state of the finger arteries below the cuff. This information
is stored every 0.5 s in the data file on disk.
A.4 Analog Input/Output
I/O voltage range
I/O Resolution
Input zero offset
Output zero offset
Internal impedance input
Internal impedance output
Output current
Output approximation
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−5 to +5 V
2.5 mV
< ±5 mV
±1% of value or ±20 mV, which ever is greater
200 kΩ
<1 Ω
max 2 mA
channel 1 & 2: linear interpolation
channel 3 & 4: staircase
A.5 Environmental specifications
Operating temperature
Storage temperature
Humidity
Ambient pressure
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10 to 40◦ C
−20 to 70◦ C
5 to 90% non--condensing
700 to 1100 hPa
A.6 Electrical specifications
Power requirements
(optionally)
Main unit fuses (two)
(optionally for 110 V)
Power cord
Protection against electric shock (EN 60601--1)
Protection against the ingress of objects or water
Power dissipation
CMOS back--up battery
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220--240 V, 50/60 Hz, 100 VA
100--120 V, 50/60 Hz, 100 VA
IEC 127, 0.8 A slow blow
IEC 127, 1.6 A slow blow
IEC 320 to local mains plug
Degree: type B applied part,
Type: Class I equipment
IP20
In Main unit: < 100 W,
in Frontend unit: 1 W,
in finger cuff: < 50 mW
3.6 V non--rechargeable Lithium,
type Sonnenschein SL--389
energy content: 1 Ah
expected life time: 20 year
A.7 Mechanical specifications
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Finometer main unit
weight
depth
width
height
Frontend
weight
depth
width
height
Arm cuff
bladder size
weight
Analog I/O connector box
d×w×h
Finger cuff
weight
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Note: all specifications rounded upwards.
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11.5 kg
45 cm
40 cm
16/41 cm (closed/open)
900 g (plus cables)
7 cm
5 cm
3 cm
Speidel & Keller
12 × 28 cm (width × length)
270 g (with two rubber tubes)
15 × 9 × 4 cm
18 - 23 g (depending on size)
A.8 Instrumental information
Product category
Product type
Measurement method
Finger cuff pressure
Arm cuff pressure
Height sensing
Data storage
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Display
VGA connector
RS--232C connector
LPT (not used)
Analog signal I/O connector
Finger cuff pump system
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Arm cuff pump system
Finometer finger blood pressure measuring device,
with Finolink and BeatScope PC--based software
Model 1
Arterial volume--clamp method of Peňáz 17; Physiocal
criteria of Wesseling 23; brachial waveform reconstruction of Bos, Gizdulich and Wesseling 2 ,6 ,7; Modelflow method of Wesseling 21; see appendix E and
the patent literature.
maximally 350 mmHg
maximally 300 mmHg
range ± 128 mmHg
On a built--in 88 MB hard disk for 24:00:00 hours,
4096 measurements maximally
10 inch VGA 640 × 480 × 16 TFT--LCD
RGB, 15 pin female, D--type
Serial port, 9 pin male, D--type
Centronics printer port, 25 pin female, D--type
4 input, 4 output, 15 pin male, D--type, ±5 V max.
Pressure regulated at 350 mmHg;
maximum pressure: 380 mmHg;
maximum air flow: 70 `/h @ 200 mmHg
Buffer pressure regulated at 800 mmHg;
maximum buffer pressure: 1150 mmHg;
maximum arm cuff pressure: 300 mmHg
A.9 Instrumental accuracy
Finger cuff pressure accuracy
Arm cuff pressure accuracy
Height accuracy
Rate accuracy
Interbeat interval accuracy
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1% of full scale (max 3 mmHg), zeroing automatic
1% of full scale (max 3 mmHg), zeroing automatic
2% of full scale (max 3 mmHg), zeroing manually
(Rate [BPM] / 60)%, thus 1% at 60 BPM
10 ms (peak, non--accumulating)
A.10 Connecting external equipment
External analog signal sources may be connected to
the analog input/output (I/O) box for sampling, and
a personal computer may be connected to the serial RS232 connector for remote data downloading.
Connecting such equipment represents a hazard to
the patient and operator as well since this equipment
may fail or may not be designed for medical usage.
Specifications have been written by the IEC for such
peripheral equipment to meet when connected indirectly, here via Finometer, and/or directly via sensors or electrodes to a patient. They are the Euro-
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pean EN 60601 standard for electromedical devices
and the IEC 950 standard for data processing devices. The department of Medical or Clinical Physics
of your hospital can advise you on how to achieve a
safe, interconnected system.
Please note that the configuration when within the
EC has to meet standard EN 60601--1--1. He who interconnects such devices is responsible for adherence
to the EN 60601--1--1 standard.
A.11 Remote control
The Finometer offers two built--in instruments to
measure finger blood pressure: the Finometer-research and the Finometer--clinique instruments
(section 4.8). The Research instrument is designed
for investigators that appreciate Finometer for the
safety from its noninvasive character, generally know
well what they are doing, and might apply Finometer to subjects under circumstances such as in an experimental laboratory or a human centrifuge. The
Clinique instrument is designed in situations when
minimal control is needed but constancy of displays
and the ability to view and appreciate the patient data presented at a glance, and operation by personnel
not specifically trained for this equipment.
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For situations when a subject has been instrumented by an investigator but must be left alone for experimental reasons, Finometer--research offers limited remote control over its operation. Only via an
externally connected personal computer running the
Beatscope or Finolink software is this control possible. Note the requirements for connecting such equip-
ment mentioned in section A.10 on page 109. The
Beatscope/Finolink software exactly reproduces the
screen interface present on Finometer allowing full
remote observation of the waveforms and data generated, with a delay not greater than 1 s of time. In
addition, the following actions can be remotely controlled from the PC by mouse or PC keyboard interaction:
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Start or stop a measurement;
Turn Physiocal off/on;
Start or stop an RTF calibration;
Record a marker signal.
It is recognized that these are the actions that may
be required during an experiment. They are the same
actions that are available from the Finometer keyboard, and can be corrected, redressed, annulled and
overridden from this Finometer keyboard or from a
remote PC acting in parallel. Note that the packet
data generated by Finometer is downloaded simultaneously by the PC and displayed.
A.12 Safe data storage—Data durability
The data packets that Finometer generates when
measuring blood pressure are stored on a built--in
storage device which presently is an ordinary PC
harddisk. On this storage medium an area is devoted uniquely to the storage of data packets. The size
of this area is such that exactly 24 hours of storage
is provided. Since packets have a size of 512 byte
and since two packets are generated each second of
time the data rate is 1024 byte/s or 1 kB/s. To store
24 hours of data the total file size is 24×60×60×1 kB
= 86.4 MB.
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Upon receiving your Finometer this file has been created and holds just empty data packets. With your
first measurement data packets are stored consecutively starting at position 0. When a measurement
is terminated a final packet is written with special
termination information.
rately maintains an index or pointer file indicating at
which position a measurement starts and stops, and
the most recent position written. If this pointer file
becomes corrupted it can be recreated (section 5.4).
When 24 hour of data packets has been written there
is no more room left and the earliest packet written,
the one at position 0, is overwritten with new data and the original file at that position is no longer
complete. This fact is also recorded in the pointer
file. Thus needed data must be downloaded regularly
to a PC using Beatscope or Finolink software. This
can be done during the measurement or afterwards.
The advantages of this system are:
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Each packet of a measurement has a unique identifier code identical for each packet. Each packet,
in addition, has a CRC, a cyclic redundancy check
(see Glossary D), to facilitate the checking of the
integrity of the packet. This checking can be used
when storing data, when transmitting it, etc.
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The system of storage is fully self contained. By inspecting the packets in a file it can be determined
where each file begins and ends, and the identifier code further allows to determine which file is the
most recent. That process is time consuming, however, since an 86 MB file has to be read sector by
512 byte sector. The storage system, therefore, sepa-
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The storage medium (the harddisk) never fills to
completion and consequently does not have to be
erased and does not require any maintenance.
The storage is very reliable such that power failures do not cause the system to crash with all
data lost.
The wear on the storage medium is minimal since
packets are always stored consecutively without
reference to file directories.
The pointer system can recover itself when corrupted.
Each packet can be checked separately for integrity.
The system operates unattended. When the
stored data is not needed no operator attention
is asked.
A.13 Unpacking—The data packets
Finometer produces data packets when measuring
finger pressure, which are stored internally and are
downloadable to a PC with the Finolink software
and/or Beatscope. Both on--line (when measuring)
and off--line downloading is possible. Each Finometer generated packet is a “molecule” of measurement
data of 512 byte size covering a 0.5 s measurement
period. Thus data is stored at a rate of 1kB/s. A
packet includes a measurement identifying signature,
a serial number, instrument diagnostics data, heart
beat derived data, four signals sampled at 200 Hz,
a marker, finally, a CCITT cyclic redundancy check
(CRC) allowing verification of the integrity of each
packet.
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Normally, the four signals stored are: finger cuff
pressure (FinAP), hydrostatic finger height (Height),
upper arm cuff pressure (Armcuf), and servo system error signal (Pleth). These signals are listed in
table 6.1. When the latter three have been replaced
by externally applied analog signals (page 73) this is
signalled in the packets, and Beatscope knows what
to do. The first (FinAP) can also be replaced by an external signal but it must be an arterial pressure wave.
In that case the external pressure signal is analysed
for beats and processed as finger cuff pressure would
be. This fact is also stored in each packet.
A packet file thus contains all the information that
used to be stored in the FAST system and in the
subsequent Beatscope system in header, samples and
results files. But packet files are more compact and
can be further compressed to ZIP files, by factors
often greater than 3. A total compression factor of
5 or more is achievable. Thus a standard CD-ROM
may hold as much as 24 days of 24 hour of continuous
monitoring.
Beatscope reads and unpacks packet files transparently and is able to display all stored data. In case
you don’t use Beatscope, however, you may still recover the header, samples, results and ASCII extended results files with Finolink. Finolink works without
a license. Start Finolink and use it to unpack the
Finometer packet files. For details see the Beatscope
1.1 User’s Guide Finolink chapter.
The header file and the ASCII results files that are
available after unpacking are readable with a text editor. It is best NOT to use proportional fonts since
information is lined up in columns. The ASCII results file can be imported directly into a spreadsheet.
The results and the samples files, however, are binary files and cannot be viewed directly except with
Beatscope.
A.14 Cleaning
The Finometer housing is made of materials that do
not easily attract dust. If cleaning is needed:
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Always first unplug the power cord.
Wipe clean using a soft, slightly moist cloth.
Never apply any liquids directly to the device or
its associated units such as frontend or analog
I/O box.
Do not immerse the device or its units in a liquid.
Never use alcohol, refined petrol, thinner or any
other chemical agents that could damage the Finometer housing.
Do not allow water or any other liquid to enter
the Finometer or its units.
Use the same cautions when cleaning the height correction system, arm cuff and finger cuff. Should water
accidentally enter a finger cuff or air hose, then try
to shake it out and allow enough time to dry.
B Error messages
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Setup errors:
− Configuration not found, save one first. You tried to load a configuration color that was not
first saved. All colors were factory pre-saved. Move to the configuration save column, highlight the
required color and press the [Configure] button. This error should not occur.
− Version incorrect, save anew. You used an older version configuration file on newer software.
Please setup this configuration again and save. This error should not occur.
Startup errors:
− Cannot start w/o frontend.
− Check air supply. No air is supplied to the finger cuff. Check if airhoses are disconnected, are
kinked or stepped on.
− Check cuff cable. Possibly a finger cuff cable hardware error. Try another finger cuff.
− Connect cuff cable. Finger cuff cable not properly connected to frontend.
− Connect frontend.
− Cuff artifact. An externally caused cuff pressure instability. Restart.
− cuff-LED problem. The LED driver servo could not set a proper LED current. Try another finger
cuff.
− Faulty finger cuff. A finger cuff hardware error. Try another finger cuff.
− Finger too thin. Too much light passes through the finger. Remove the finger cuff. Wrap a dark
colored thin cloth or plastic sheet around the finger then reapply the finger cuff.
− Gain switch malfunction. A hardware error. If it occurs repeatedly please contact FMS, see
page 3.
− No plethysmogram. No plethysmogram was observable, possibly due to full finger artery contraction.
Try to warm the hand, see section 4.3 on page 37.
− Nonstop switch malfunction. A hardware error. If it occurs repeatedly please contact FMS, see
page 3.
− Pointer file not updated, this file lost. A hardware error. For recovery turn Finometer off,
then on; see section 5.4.
− Unstable pressure. The finger cuff air pressure servo could not stabilize pressure in the required
amount of time. Check if air hoses are disconnected, are kinked or stepped on.
Run time errors:
− Mean pressure too high. The mean finger cuff pressure was too high for 1 s. This may be an
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artifact but could be a potentially serious error. Try once more.
− Measured 12 h on this finger. An uninterrupted measurement of 12 h on a single finger possibly
approaches a safe limit. Wrap the cuff on another finger or allow a rest period of at least 5 min.
Restart.
− Premature operator stop. You stopped the measurement while it was in startup. Restart.
− Pressure low--check air hose. The finger cuff air hose may have become dislodged. Reinsert
firmly. Restart.
− Pressure too low. The run time finger cuff pressure reached unphysiologically low levels. This may
be a movement artifact. Restart.
− Reconnect front end. The frontend cable was removed during a run. Reinsert the connector firmly,
see section 2.1 on page 20. Restart.
− Reconnect height sensor. The hydrostatic height correction system was disconnected while measuring rendering erroneous finger pressures. Reconnect and restart
− Semaphore overrun. A hardware error. If it occurs repeatedly please contact FMS, see page 3.
− Unacceptable plethysmogram. The plethysmogram values moved out of range. This may be a
movement artifact. Restart.
Arm cuff errors:
− Arm cuff overinflated. An arm cuff pressure of greater than 300 mmHg was maintained too long.
Usually a serious hardware error. Please immediately contact FMS, see page 3.
− Arm cuff still inflated. After an arm cuff over pressure situation deflation to zero pressure has
taken too long. Remove arm cuff immediately. Usually a serious hardware error. Please contact FMS,
see page 3.
− Calibration cycle compleat. An arm cuff calibration cycle went up and came down, then stopped.
This is not an error but a safety measure. Restart for another cycle.
− Check arm cuff air supply. The arm cuff air buffer does not reach proper pressures. There may
be a leak or the pump malfunctions. Please contact FMS, see page 3.
− Connect both cuff tubes to Finometer.
− Cuff deflation not linear. May be due to artifact. If the error is systematic it is a hardware
error. Please contact FMS, see page 3.
− Deflation stopped, cuff pressure<20 mmHg. A Classico measurement stops when cuff pressure
moves below 20 mmHg. This is not an error. Usually the operator would have stopped the measurement manually.
− Measurement stopped, taking too much time. Inflation to a high pressure and deflation at a very
slow rate may take longer than normal. A safety measure.
C Derived parameters
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Symbol
Color
Meaning
SYS
DIA
MAP
Red
Red
White
IBI
HR
LVET
Gray
Red
Gray
SV
White
CO
TPR
Cyan
Yellow
SPTI
—
DPTI
—
systolic pressure as the maximum pressure in arterial systole
diastolic pressure as the low pressure just before the current upstroke
mean arterial pressure as the true integrated mean pressure
between the current and the next upstroke
pulse interval as the time between the current and the next upstroke
pulse rate derived from the pulse interval
left ventricular ejection time as the time between the current upstroke and the dicrotic notch
stroke volume as the true integrated mean of the simulated flow waveform between
the current upstroke and the dicrotic notch
cardiac output as the product of stroke volume and heart rate
total systemic peripheral resistance as the ratio of mean arterial pressure to cardiac
output, assuming zero venous pressure (at the right atrium)
systolic pressure time index, the area under the reconstructed aortic pressure waveform in systole, between begin upstroke and the dicrotic notch, not separately available
diastolic pressure time index, the area under the reconstructed aortic pressure waveform in diastole, between the dicrotic notch and begin upstroke of the next beat, not
separately available
diastolic to systolic pressure time index ratio as an index of cardiac oxygen supply
and demand, always computed off a reconstructed aortic pressure waveform
time--tension index (rate pressure product) as an index of cardiac oxygen demand,
computed as the product of systolic pressure and pulse rate
maximal steepness of the current upstroke always computed on the finger pressure
waveform
ascending aorta characteristic impedance at diastolic pressure
total arterial compliance at diastolic pressure
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D/SPTI
Green
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PS*HR
Magenta
dp/dt
Blue
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Zao
Cwk
Green
Magenta
Table C.1 Finometer derived parameters. All parameters when displayed are 8--beat averages. Indexed
parameters have a darker shade. The clinique waveform display shows beat--to--beat heart rate in Yellow.
D Glossary
A/D converter see “converter A/D”.
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baroreflex sensitivity Expresses the change in
interbeat interval, in ms, for a simultaneously occurring change in blood pressure, in mmHg. It is
thought to principally represent the sensitivity of vagal heart rate control upon blood pressure changes
and to a lesser degree on sympathetic control. Its
value in normal subjects tends to depend on blood
pressure, on heart rate, and subject age. The measurement can be performed in various ways, evoked or
spontaneous, sequential or spectral. The distribution
of a number of BRS observations is almost always
log--normal and non--parametric statistics are called
for. If a mean value is computed the best approach
usually is to take the geometric mean.
Beatscope
A computer program available from
FMS featuring ”click and go” connection of a PC
to Finometer (or to Portapres), display of waveforms and derived parameter trends, extraction of
data epochs to separate files for analysis with spreadsheets, Matlab, computation of descriptive statistics
and production of publishable graphics.
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bias The mean difference between the results of
measurements of the same parameter with two methods in several subjects. The method under test
may show biased results with respect to a reference
measurement. For example, finger diastolic pressure
shows a negative bias with respect to intrabrachial
artery pressure.
BNC connector A coaxial type connector designed
originally for high frequency signals but also used
with advantage to pass low frequency signals such
as ECG, EEG, BCG, BAP, EMG, respiration in a
continuously shielded manner. Easy to connect and
disconnect.
COM port A communications port of a PC which
is available under most operating systems and which
passes data serially, and asynchronously, in start/stop
mode. These ports follow the RS-232 standard in
personal computers.
converter A/D Converts an analog voltage signal to a digital data stream. Measures the value of
an analog, continuously variable signal at fixed increments of time converting its instantaneous value to a
number which can be handled by a digital computer.
The numbers are usually stored in a file on harddisk
and when displayed interconnected with straight lines
restore the impression of the original continuous signal. At the sample rate used in Finometer of 200 Hz
the fixed time increment is 0.005 s or 5 ms.
converter D/A Changes a stream of numbers at
fixed increments of time usually to a step wise varying
analog signal for plotting and viewing. The two Finometer analog output ports labelled output 1 and
output 2 use linear interpolation, not step wise variation, for a smooth output signal. This requires special analog output circuitry and causes a 5 ms delay
since the line can be “drawn” to the next point only
when it is known.
cyclic redundancy check A system used to secure
communication of data streams in packets between
computers and allowing to test after transmission of
the packet if transmission occurred without error. In
case of an error a repeat transmission can be requested. Finometer applies a CCITT (the telecommunications standards committee) CRC for all its data
packets. It is generated and added to each packet
before storage to disk or transmission over a port
to an external device such as a personal computer.
When Finolink is used for communication this program checks the CRC and in case an error is detected requests re-transmission by Finometer until the
packet is received correctly.
D/A converter see “converter D/A”.
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deflation rate The speed with which a Finometer
arm cuff is deflated expressed in mmHg/s. Deflation is linear for the Finometer, controlled by a servo
system. For best precision a slow deflation is chosen.
For return--to--flow calibrations at normal blood pressures the deflation rate is near 2 mmHg/s, for higher
blood pressures it is slightly faster.
derived parameters Measurements made on the
pressure or flow pulsation available in Finometer.
The pressure pulsation (figure D.1), default, is the
reconstructed brachial artery (reBAP) pulse, but the
original finger pressure (FinAP) pulse may optionally
be chosen. The flow pulse used is generated by the
Modelflow algorithm and does not depend on brachial pressure reconstruction. Derived parameters de-
Figure D.1
Some derived parameters.
scribe a patient’s state. Finometer provides for many
such parameters mostly measured on a beat--to--beat
basis.
downloading The process by which data is received
from another (central) computer system and loaded
into local store. In Finometer’s context downloading
is performed by a PC running Finolink software to
obtain packet files from a Finometer. The process is
initiated from and controlled by Finolink. Finometer
takes care that the requested packet is transmitted
over the cable.
Finapres Finapres TM, acronym for FINger Arterial PRESsure, was the first commercially available
device to measure finger blood pressure continuously according to the volume--clamp method of Peňáz
and the Physiocal criteria of Wesseling. Portapres
and Finometer are successors of Finapres. Finapres
is no longer marketed.
Figure D.2
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A finger cuff.
finger cuff A conical shaped inflatable cuff, with an
extremely thin bladder, coming in three sizes fitting
most fingers from the age of 6 years. On the inside an
infrared plethysmograph is mounted to monitor the
size of the arteries under the cuff (figure D.2).
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Finolink A Windows software program provided by
FMS to be used to download the packet files generated by Finometer. Downloading with Finolink can
be done off--line (when Finometer is not connected
to a patient performing a measurement) or on--line.
When off--line downloading each and every file can
be selected for downloading. When on--line only the
file and packets currently being generated and stored
can be downloaded.
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Finometer The commercial successor of Finapres
but with many extras such as hydrostatic finger to
heart level compensation, brachial artery pressure
reconstruction, return--to--flow calibration and Modelflow cardiac output computation. These methodologies are described in corresponding papers in the
scientific literature and implemented. They aim at
improved accuracy of measurement. Many derived
parameters are computed on the pressure and flow
waveforms and can be selected for display and trending.
FMS FMS, Finapres Medical Systems BV. A company established under the law of the Netherlands
with its seat in Arnhem, to manufacture, market,
sell and service Finapres based devices and software.
FMS is a spin off of TNO TPD Biomedical Instrumentation at the Academic Medical Centre in Amsterdam. The current product line consists of Portapres, Finometer, Beatscope, and WinCPRS, the
latter in collaboration with AA Oy in Finland.
frontend A small box to be mounted near the patient’s cuffed finger containing amplifiers, a pressure
transducer and a fast air pressure control valve, implementing the volume--clamp method of Peňáz. The
hydrostatic height correction system is also operated
from the frontend box.
generalized A method or result valid for a population of subjects on average with little interindividual
spread. The transfer function from intrabrachial to
finger pressure, for example, is nearly identical for
most subjects, and independent of clinical condition
and, therefore, generally correct.
heart rate variability A term to describe variations of both instantaneous heart rate and RR inter-
vals. Heart rate variability represents a marker of autonomic activity which has a significant relationship
with cardiovascular mortality. HRV can be measured
in many different ways, in the time domain and in the
frequency domain, and many computed parameters
increase in value with the duration of the record. In
1996 a report was published by an international Task
Force, bringing order in this complex matter and recommending that at least four measures be computed
in the time domain: SDNN as an estimate of overall HRV; HRV triangular index as another estimate
of overall HRV, based on the RR interval histogram;
SDANN as an estimate of long--term components of
HRV; RMSSD as an estimate of short--term components of HRV. NN represents consecutive intervals
between sinus beats.
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hydrostatic height A vertical column of liquid
has a higher pressure at the bottom than at the top.
Thus, finger pressure measured with the arm hanging
down is higher than when the finger is at heart level.
The effect is substantial. A 1.3 cm difference in height
causes a 1 mmHg difference in pressure. The hydrostatic height correction system measures the relative
vertical positions of hand and heart and automatically compensates for any measured difference. This
removes a major source of uncertainty in finger blood
pressure measurement.
I/O Input/Output. A general term denoting the
transfer of information between two (computer) systems. A person may input information to a computer
by typing on an attached keyboard. A computer outputs information by displaying it on a screen.
I/O analog Input and/or output of analog signals to and from a system such as Finometer. It is
performed with A/D and D/A converters and the information transferred is an analog signal such as a
voltage proportional to a blood pressure pulsation.
I/O parallel Input/output of digitally coded information when not bits but words are transferred over
a number of parallel wires, usually between two computers or between a PC and the computer embedded
in Finometer. Parallel I/O is often transferred via
printer ports. Potentially faster than serial I/O.
I/O serial Input/output of digitally coded information as a modulated voltage bit stream over a single wire usually between two computers or between a
PC and the computer embedded in Finometer. Serial
I/O is transferred via a COM port and is subjected
to strictly standardized protocols.
inflation rate The speed in mmHg/s with which an
upper arm cuff is inflated. Finometer uses a special
pneumatic circuitry to allow full arm cuff inflation
in only one or two seconds. Such fast yet smooth
inflation limits the pooling of blood in vessels distal
of the cuff and thus is often considered more pleasant
than slow inflation. In addition it provides for clearer
Korotkoff sounds and reduces the auscultatory gap.
level correction A procedure that shifts finger
pressure usually in an upwards direction to approach
brachial artery pressure levels more closely, thus correcting for the pressure decrement that generally exists between brachial and finger blood pressures. The
amount of correction depends on the relative levels of
systolic and diastolic pressure.
light emitting diode An electronic component
that transmits almost monochromatic light when an
electrical current is passed through it. Finometer finger cuffs contain an LED that transmits light in the
infrared. Infrared light is invisible.
the area under the flow pulse in systole. Cardiac output is the product of stroke volume and heart rate.
Total systemic peripheral resistance equals the sum
of Z0 and Rp . In Finometer TPR is computed and
averaged differently and displayed in different units.
Modelflow provides close tracking of changes in cardiac stroke volume and output. Entry of patient gender, age, height and weight are required for best precision.
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Figure D.4
Figure D.3
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Nonlinear curves.
The Modelflow model.
Modelflow A method and algorithm to compute
an aortic flow curve from an arterial pressure pulsation by simulating a nonlinear, self--adaptive model of
the aortic input impedance. The three--element model (figure D.3) is well known from physiology for its
ability to compute stroke volume. The aortic characteristic impedance, Z0 , and Windkessel compliance,
Cw , are nonlinearly depending on arterial pressure,
p, the peripheral resistance, Rp , adapts to changes in
mean flow, q̄. Stroke volume is computed by taking
nonlinear A relationship is nonlinear when the plot
of a dependent variable against an independent variable is curvilinear. For example aortic volume, V,
when plotted against blood pressure is nonlinear since
aortic volume does not increase linearly with increasing pressure but at higher pressures increases less and
less. Compliance, C, plotted against pressure is also
highly nonlinear. Furthermore, aortic nonlinearity is
age dependent as can be seen by comparing the curves
for an elderly (upper left) and a young adult subject
in the above diagrams D.4.
nulling Reducing the zero offset of a transducer to
null. Devices such as semiconductor pressure transducers convert pressure into voltage, and do that linearly. However, at zero applied pressure there may
already be a positive or negative voltage output also
called zero offset. This should be removed (nulling)
and is done by first measuring and then subtracting
the zero offset such that the resultant output is 0 V
at 0 mmHg.
measurement information. Each packet is given a
cyclic redundancy check value (CRC) as soon as it
is assembled. Thus at any storage or transfer action
the packet’s integrity can be verified. Packets are
grouped into files. A measurement file consists of a
number of packets with each packet having a sequential number and the file being terminated with a last
packet containing extra information not present in a
normal packet.
null modem cable A computer is designed to communicate in serial fashion over a COM port with passive, non--computer attached devices such as printers
or a modem. If computers want to communicate to
each other instead of to a passive device they get confused unless they are connected via a ‘null-modem’
cable. This applies to the Finometer embedded computer when it needs to communicate with a PC.
Peňáz method The Czech professor of Physiology Dr Jan Peňáz working in Brno, invented the volume--clamp method whereby the volume of the arteries under a finger cuff, as observed by a photo--electric plethysmograph, is dynamically held constant by
precisely measured counter pressure in the finger cuff
during the pulsation, using a pneumatic servo system.
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off--line A device is called ‘off--line’ when it is operating independently of a central computer. For Finometer we use the expression when it is not connected to a patient performing a finger pressure measurement.
photocell An electronic component or device which
responds to light by generating an electrical current. In a Finometer cuff a photocell is mounted
which is principally sensitive in the infrared to observe changes in light from an LED proportional to
changes in arterial volume.
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offset A steady, systematic difference or shift between the actual value and the reference or ideal value.
on--line The opposite of ‘off--line’. Finometer is
on--line when connected to patient and performing a
measurement.
packet For Finometer a packet is 512 byte of data in a predefined format and representing 0.5 s of
Physiocal Acronym for Physiologic Calibration.
The algorithm that calibrates the finger arterial size
at which finger cuff air pressure equals finger arterial
blood pressure. During a Physiocal cuff air pressure
is held at varying levels and the plethysmogram is
observed that is caused by the pulsating intraarterial
pressure. The amplitude and shape of the plethysmogram determine the volume--clamp level.
plethysmogram
A graphic representation of vol-
ume changes with time of a part of the body such as a
finger or arm. In Finometer the finger arterial volume
changes (finger plethysmogram) are recorded in the
infrared. Red blood cells absorb infrared light strongly. A larger vascular volume contains more red cells
and absorbs more infrared. Thus, a more distended
blood vessel is recorded as a decreased brightness.
precision The amount of scatter in the difference
between values of a variable such as blood pressure
measured by two independent methods. For example, when blood pressure is measured intraarterially
in the brachial artery and noninvasively in the finger
the systolic levels may differ each beat. The difference can be expressed statistically as the mean difference and the standard deviation of the difference.
The mean difference is also called bias. The standard
deviation is also called precision.
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random zero A zero offset of unknown and random value is introduced to the mercury column of the
Hawksley Random Zero sphygmomanometer. This
causes the readout of cuff pressure to be in error.
At the completion of a measurement the zero offset is measured separately and subtracted from the
readouts to obtain correct measurement values. The
procedure reduces operator bias and digit preference.
In the Finometer--classico instrument, when set to
‘random zero readout’ the zero offsets range in value between −15 and +15 mmHg. Their randomness
or unpredictability is guaranteed by using a digital
random number generator. After the measurement
the zero offset is subtracted automatically from any
marked cuff pressures.
receptacle Usually the chassis mounted part of a
connector to receive the cable mounted part of the
connector.
return--to--flow
A method, different from Korotkoff sounds but similar to palpation, to detect the
instant that cuff pressure equals intraarterial systolic
pressure. The term originates from the detector used,
an ultrasound Doppler flow meter. In Finometer the
finger pressure distal of the occluding cuff is monitored for return of pressure pulsations.
revolving store A storage area or buffer in computer memory or on harddisk which is addressed in a
circular fashion starting at the beginning, moving towards the end, then restarting at the beginning, and
so forth. In Finometer, such a storage area is reserved
on harddisk. It consists of 24 × 60 × 60 × 2 packets
of 512 byte size to a total size of 172800 packets or
88,473,600 byte. Finometer maintains an index into
the store holding the starting points of each separate
file. When this pointer file is disturbed, for example
by switching the power off during a measurement, it
has to be recreated. This is a time consuming process. Because the store is a revolving store which
overwrites itself, it does not have to be erased. Hence,
there is no need for erasure facilities.
rise time The time it takes for a pulse to rise from
bottom to top or, more precisely, from 10% up to 90%
up. The rise time of a finger pressure pulse is typically
100 ms or 0.1 second. When it is much slower than
100 ms the operator is alerted. Slow rise times may
occur due to proximal plaques or other hemodynamic
obstructions.
RS-232
An international standard for asynchronous serial communication of digital information
over a COM port. Among other things it sets communication rates expressed in baud or in BPS for bit
per second, number of start and stop bits and parity checking. All this is automatically set up between
Finometer and a PC running the Finolink software.
RTF calibration A technique used in Finometer to compare the return--to--flow systolic pressure
with the waveform filtered finger pressure. An optimal pressure increment or decrement is computed
to make reconstructed brachial pressure levels nearly
identical to intrabrachial levels.
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sensitivity One pressure transducer may react to
a 1 mmHg pressure variation by changing its output by 8, another by 15 mV. Thus sensitivity is 8
or 15 mV/mmHg. For Finometer it is a requirement
that sensitivity is exactly 10 mV/mmHg or 1 V per
100 mmHg. Finometer pressure transducer sensitivity can be checked but if it deviates more than the
specification it cannot be adjusted in the field but
must be returned to the manufacturer. It is believed
that the semiconductor pressure transducers in Finometer maintain their calibration over many years.
serial I/O see “I/O serial”.
square wave A waveform that changes stepwise in
time from a low to a high level. A square wave is well
suited as a calibration signal since many properties
of a recording system can be tested with it. Finometer outputs a square wave on all four analog output
connectors when it is not performing a measurement
Figure D.5
Square wave calibration.
(when it is off--line). For best performance it moves
between three (0, 1 and 2 V) not two levels, and at
the two frequencies, 1 and 0.1 Hz (figure D.5).
TNO The Dutch Organization for Applied Scientific Research. TNO operates a number of Institutes.
TPD is the TNO institute of Applied Physics having its seat in Delft, The Netherlands. Biomedical
Instrumentation (BMI) is a division of TPD and is
located at the Academic Medical Center of the University of Amsterdam. The Finapres, the Portapres,
the Modelflow method, the Beatscope software, and
the Finometer were developed at BMI and are now
available from FMS, Finapres Medical Systems BV.
transducer A device or component that changes
one mode of physical power into another. Finometer
can be called a transducer. It changes blood pressure
into air pressure and further into an electrical voltage that can be amplified, filtered, sampled digitally,
displayed, etc..
transfer function A mathematical equation describing how frequencies in one waveform, for example the brachial pressure waveform, are amplified or
the arterial walls in the finger under the cuff.
Figure D.6
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Transfer functions.
attenuated in another related waveform such as the
finger pressure. The brachial to finger pressure transfer function (thin line in figure D.6) shows attenuation for low and amplification for higher frequency
components, in particular near the frequency of 8 Hz.
unloading Removing the load of a construction or
component. Arterial walls carry the load of the blood
pressure that tries to expand the arteries from the
inside. By applying a counter pressure from the outside the arterial wall can be unloaded. The counter
pressure then carries the load. If blood pressure has
a pulsatile component on top of a mean distending
pressure then unloading can be done statically, only compensating for the mean pressure, or it can be
done dynamically, thus also countering the pulsatile
component. Finometer does a dynamic unloading of
waveform filtering Applying a frequency dependent filter to a waveform to change its shape in a
predetermined way. Waveform filtering is used in Finometer to change a finger to a brachial artery blood
pressure waveform. This includes amplifying frequencies below 2.5 Hz by a factor slightly greater than one
and attenuating frequencies near the 8 Hz resonance
peak that occurs in the transmission path between
brachial and finger artery sites. Waveform filtering is
akin to applying a transfer function to a signal but
it is done in real time almost without delay and does
not use Fourier transforms.
Wesseling criteria
Noninvasive blood pressure
measurements with an occluding cuff require a criterion to detect when cuff pressure equals an intraarterial
pressure level. For the oscillometric method of Marey,
MAP is the cuff pressure at maximum cuff pressure
oscillations. The volume--clamp method of Peňáz
dynamically unloads finger arterial volume, and the
Wesseling criteria establish the (setpoint) volume at
which finger cuff pressure equals intraarterial blood
pressure. Since this setpoint volume is under sympathetic influence the calibration has to be repeated
regularly. Physiocal is the computer implementation
of these criteria.
zeroing
see “nulling”.
E Literature references
1. AAMI: American national standard ANSI/AAMI
SP10--1992: Electronic or automated sphygmomanometers. Association for the Advancement
of Medical Instrumentation, 1993, Arlington, VA.
2. Bos WJW, van Goudoever J, van Montfrans GA,
van den Meiracker AH, Wesseling KH: Reconstruction of brachial artery pressure from noninvasive finger pressure measurement. Circulation
1996; 94:1870--1875.
3. O’Brien E, Mee F, Atkins N, O’Malley K: Inaccuracy of the Hawksley random zero sphygmomanometer. The Lancet 1990; 336:1465--1468.
page 126
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4. Castiglioni P, Parati G, Omboni S, Mancia G,
Imholz BPM, Wesseling KH, DiRienzo, M: Broadband spectral analysis of 24 h continuous finger blood pressure: comparison with intra-arterial
recordings. Clin Sci 1999; 97:129--139.
5. Fitzgerald DJ, O’Malley K, O’Brien E: Inaccuracy of London School of Hygiene sphygmomanometer. BMJ 1982; 284:18--19.
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6. Gizdulich P, Imholz BPM, van den Meiracker AH,
Parati G, Wesseling KH: Finapres tracking of systolic pressure and baroreflex sensitivity improved
by waveform filtering. J Hypertens 1996; 14:243-250.
7. Gizdulich P, Prentza A, Wesseling KH: Models of
brachial to finger pulse wave distortion and pressure decrement. Cardiovasc Res 1997; 33:698-705.
8. Gravenstein JS, Paulus DA, Feldman J, McLaughlin G: Tissue hypoxia distal to a Peňáz finger
blood pressure cuff. J Clin Monit 1985; 1:120-125.
9. Harms MPM, Wesseling KH, Pott F, Jenstrup
M, van Goudoever J, Secher NH, van Lieshout
JJ: Continuous stroke volume monitoring by modelling flow from non-invasive measurement of arterial pressure in humans under orthostatic stress.
Clin Sci 1999; 97:291--301.
10. Imholz BPM, Wieling W, Langewouters GJ, van
Montfrans GA: Continuous finger arterial pressure: utility in the cardiovascular laboratory. Clin
Autonomic Res 1991; 1: 45--53.
11. Imholz BPM, Langewouters GJ, van Montfrans
GA, Parati G, van Goudoever J, Wesseling KH,
Wieling W, Mancia G: Feasibility of ambulatory, continuous, 24-hour finger arterial pressure
recording. Hypertension 1993; 21:65--73.
12. Imholz BPM, Wieling W, van Montfrans GA,
Wesseling KH: Fifteen years experience with finger arterial pressure monitoring: assessment of
the technology. Cardiovasc Res 1998; 38:605--616.
13. Jansen JRC, Schreuder JJ, Mulier JP, Smith NT,
Settels JJ, Wesseling KH: A comparison of Modelflow cardiac output derived from the arterial
pressure wave against thermodilution in cardiac
surgery patients. Br J Anaesth 2001; 87:212--222.
14. de Jong-de Vos van Steenwijk CCE, Wieling W,
Johannes MD, Harms MP, Kuis W, Wesseling
KH: Incidence and hemodynamic characteristics
of near-fainting in healthy 6 to 16 year old subjects. JACC 1995; 25:1615--1621.
15. Langewouters GJ, Wesseling KH, Goedhard WJA:
The static elastic properties of 45 human thoracic
and 20 abdominal aortas in vivo and the parameters of a new model. J Biomech 1984; 17:425-435.
of two prototype devices producing noninvasive,
pulsatile, calibrated blood pressure measurement
from a finger. J Clin Monit 1985; 1:17--29.
19. Task Force: Heart rate variability. Standards
of measurement, physiological interpretation, and
clinical use. Eur Heart J 1996; 17:354--381.
20. Wesseling KH: A century of noninvasive arterial
pressure measurement: from Marey to Peňáz and
Finapres. Homeostasis 1995; 36:50--66.
21. Wesseling KH, Jansen JRC, Settels JJ, Schreuder
JJ: Computation of aortic flow from pressure in
humans using a nonlinear, three-element model.
J Appl Physiol 1993; 74:2566--2573.
16. van Lieshout JJ, Wesseling KH: Continuous cardiac output by pulse contour analysis? Br J
Anaesth 2001; 86:467--469 (Editorial II).
22. Wesseling KH, Smith NT: Availability of intraarterial pressure waveforms from cathetermanometer systems during surgery. J Clin Monit
1985; 1:11--16.
go back
17. Peňáz J: Photoelectric measurement of blood
pressure, volume and flow in the finger. Digest
10th Int Conf Med Biol Engng. Dresden, 1973; p
104 (abstract).
23. Wesseling KH, de Wit B, van der Hoeven GMA,
van Goudoever J, Settels JJ: Physiocal, calibrating finger vascular physiology for Finapres.
Homeostasis 1995; 36:67--82.
index
18. Smith NT, Wesseling KH, de Wit B: Evaluation
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F Index
24 h measurement store
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111
a
A/D converter—Glossary 117
Accessing files 22, 111
Accuracy 108
Analog I/O
blood pressure signal 21
BNC connectors 21
calibration selection 46
calibration signal 19
calibration signal properties 46
calibration waveforms 46
configurability 73, 74
connector 20
external input 23
external pressure wave 73
external signals 23
external signal safety 18, 109
height signal 21
off--line calibration 46
sampling rate 29, 74
specifications 103
Analog input 103
Analog output 103
Arm cuff over pressure protection 67, 101
Arm cuff wrapping 63
Arteriosclerosis 37
Auscultation 91
Availability of finger pressure 17
Averaging 52, 59, 64, 87, 89, 91
Avoiding injury 18, 109, 110
b
Baroreflex sensitivity—Glossary 117
Battery 105
Beatscope 5, 22, 29, 44, 51, 56, 84, 100, 111, 112
Beatscope—Glossary 117
Bias and precision
arterial pressure 32
cardiac output 32
Classico 91
definition 32
Bias—Glossary 117
Bibliography 126
BNC connector—Glossary 117
Brachial pressure reconstruction
derived parameters 31
level calibration 42
level correction 41
setting up 72
Browsing with mouse and buttons 7
BRS—Glossary 117
Buffer 67
Button functions of Interactive User’s Guide 7
c
Calibration
arm cuff transducer 71, 94
buffer pressure 67
Classico waveform 94
external signal 73
finger pressure transducer 70
Finometer pressures 28
height transducer 69
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Modelflow 16, 82
Modelflow
by aortic diameter 57
by thermodilution 57
not possible 45
physiologic 62
pressure level 42, 72
pressure transducers 18, 65
pressure wave 46
return--to--flow 31, 32, 63, 88, 90
return--to--flow display 90
service 3
signal during downloading 47
signals 29, 44, 46
signal selection 46
slide 42
square wave 46
transducer stability 70
use other arm 37
Cannot start 48
Cautions 17
CE marking 97
CGS unit system 77
Chapter
classico instrument 91
clinique instrument 81
customer support 3
Dear Guide user 7
disclaimer 5
error messages 114
glossary 117
help slides 34
introduction 26
literature references 126
quick start 19
research configuration 65
research instrument 49
specifications 97
start display 44
warnings 16
Classico instrument
auscultation 95
blinded readout 95
calibration 94
display layout 93
Hawksley Random Zero 96
introduction 91
London School of Hygiene 95
random zero 96
results download 93
Riva--Rocci/ Korotkoff 95
setup deflate 93
setup inflate 93
setup readout 93
Cleaning 113
Clinique instrument
control
idling 86
measuring 88
off--line 86
describe subject 82
display compression 89
display layout 87
error message display 83
files downloading 84
height nulling 86
hidden Modelflow 81
introduction 81
return--to--flow 90
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setting patient data 82
show trends 85
status line 87
Clock setup 75
Cold fingers 37
COM port—Glossary 117
Configuration
date and time 75
display units 77
external signal channel 74
external signal input 73
finger switching 76
load 80
miscellaneous 76
overview 65
pressure waveform reconstruction 72
save 79
system beeper 78
time and date 75
transducer check
arm cuff 71
buffer pressure 67
finger cuff 70
height calibration 69
height nulling 68
Connecting external equipment 109
Control
buttons 21, 40, 88
Clinique 86, 88
Finometer 40
remote 18, 54, 81, 84, 109, 110
Research 52
servo system state 62, 102
tab cards 52
Converter A/D—Glossary 117
Converter D/A—Glossary 117
Costo--clavicular cutoff 37
CRC—Glossary 118
Cuff application 36
Cuff sizing 35
Customer support 3
Cyanotic finger tips 38
Cyclic redundancy check—Glossary
d
D/A converter—Glossary 118
Data file erasure 111
Date and time 75
Deflation rate—Glossary 118
Derived parameters 31, 116
Derived parameters—Glossary 118
Describe subject
Clinique 82
Research 51, 56, 57
Dimensions 106
Disclaimer 5
Display layout
Classico 93
Clinique 87
Research 52
Downloading 22, 44, 109, 110, 111
Downloading
Clinique 84
Finolink 5
off--line 47, 54, 84
on--line 54, 84
Research 54, 110
Start display 47
Downloading—Glossary 118
118
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e
ECG 74
Electrical hazards 109
Electrical safety 101
Electrical specification 105
Environmental specification 104
Error message
list of 114
Error message display
Classico 93
Clinique 83
Research 53
EXIT 40
External signals
analyze pressure waveform 74
channel select 74
offset 73
polarity 73
sampling 23
sensitivity 73
f
Failure 48
Features 29
Files downloading 111
Files downloading, see Downloading
FinAP 31, 32, 52, 61, 74, 86, 87
Finapres
cuff 38
Finometer mode 30, 72, 79, 80
Ohmeda Model 2300 27
oxygen saturation 38
trade mark 5
Finapres and Finometer 28
Finapres—Glossary 118
5
Finger cuff over pressure protection 101
Finger cuff—Glossary 119
Finger switching pressure differences 76
Finolink 107, 112
Finolink
approved software 18, 110
Classico download 93
Clinique download 84
file name 75
off--line download 47
packets 54
remote control 29
Research download 54
setting up 22, 110
Start display 44
trade mark 5
Finolink—Glossary 119
Finometer
application safety 16
cannot start 48
description 27
ease of use 6
EXIT 40
features 29
instruments 30
level calibration 42
level correction 41
methods 28
three built--in instruments 6
trade mark 5
user interfaces 30
Finometer and Finapres 28
Finometer component parts 99
Finometer in a system 109
Finometer—Glossary 119
FMS 3
FMS—Glossary 119
Frontend—Glossary 119
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g
Generalized—Glossary 119
General system protection 102
Glossary
A/D converter 117
baroreflex sensitivity 117
Beatscope 117
bias 117
BNC connector 117
BRS 117
COM port 117
converter A/D 117
converter D/A 117
CRC 118
cyclic redundancy check 118
D/A converter 118
deflation rate 118
downloading 118
Finapres 118
finger cuff 119
Finolink 119
Finometer 119
FMS 119
frontend 119
generalized 119
heart rate variability 119
HRV 119
hydrostatic height 120
I/O 120
I/O analog 120
I/O parallel 120
I/O serial 120
inflation rate 120
LED 121
level correction 120
light emitting diode 121
Modelflow 121
nonlinear 121
nulling 122
null modem 122
off-line 122
offset 122
on-line 122
packet 122
Peňáz method 122
photocell 122
Physiocal 122
plethysmogram 122
precision 123
random zero 123
receptacle 123
return-to-flow 123
revolving store 123
rise time 123
RS-232 124
RTF 123
RTF calibration 124
sensitivity 124
serial I/O 124
square wave 124
TNO 124
transducer 124
transfer function 124
unloading 125
waveform filtering 125
Wesseling criteria 125
zeroing 125
h
Hawksley Random Zero 91
Heart rate variability 74
Heart rate variability—Glossary 119
Height correction 39
Height system
nulling 39, 40
sensitivity 39
Help slides 34
Hibernate 48
HRV 74
HRV—Glossary 119
Hydrostatic height system 69
Hydrostatic height—Glossary 120
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i
I/O analog—Glossary 120
I/O parallel—Glossary 120
I/O serial—Glossary 120
I/O—Glossary 120
IEC standard 601 109
IEC standard 950 109
Impedance internal 103
Inflation rate—Glossary 120
Input 103
Inspection incoming 99
Instruction slides 34
Instrumental accuracy 108
Instrumental specification 107
Instruments 30
Introduction
Classico 91
Clinique 81
Finometer 26
Research 49
Start display 34
k
Korotkoff
91
l
LED—Glossary 121
Level calibration 42, 72
Level correction 41, 72
Level correction—Glossary 120
Light emitting diode—Glossary 121
Litterature 126
Loading a configuration 25, 80
London School of Hygiene 91
m
Mark button 40
Mechanical specification 106
Medical unit system 77
Methods in Finometer 28
mmHg 77
Modelflow
bias and precision 32
calibration from aortic diameter 57
calibration from thermodilution 57
Clinique 81
flow curve 52
from external signal 74
head--up tilt 82
linear scaling 82
methodology 28
not displayed 81
patient data 51, 56
trade mark 5
Modelflow—Glossary 121
n
Nonlinear—Glossary 121
Nulling—Glossary 122
Null modem 22, 44, 109, 110
Null modem—Glossary 122
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o
Off-line—Glossary 122
Offset—Glossary 122
On-line—Glossary 122
Ordering parts 3
Output 103
Over pressure
arm cuff 67, 101
finger cuff 101
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p
Package checklist 99
Packet file
A/D signals 61
accessing 5, 22
Clinique trend plot 88
contents 111, 112
date and time 75
display compression 89
downloading 44, 47, 84, 111
erasing data 111
erasing memory 47, 54
error message 53, 83
identical 81
index 111
internal signal not stored 23
naming convention 75
return--to--flow data 90
size 111
stop plotting 88
unpacking 22, 112
Packet—Glossary 122
pascal 77
Patient data
Clinique instrument 82
Research instrument 51
Patient safety 100, 109
Patient sensors 21
Peňáz method—Glossary 122
Peripheral resistance 77
Photocell—Glossary 122
Physiocal 28
Physiocal
Clinique 88
diagnostics 62
displayed 61
grading quality 62
off/on 54, 62, 110
Research 62
Physiocal—Glossary 122
Plethysmogram—Glossary 122
Pointer file
corrupted 48, 111
recreation 48, 111
Power dissipation 105
Precision—Glossary 123
Protective measures 18, 109, 110
q
Quick start
accessing files 22
equipment setup 19
external signals 23
loading a configuration 25
patient sensors 21
saving a configuration 25
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r
Random zero—Glossary 123
Readout Classico
blinded 95
calibration 94
markers 95, 96
normal 95
random zero 96
reBAP 31, 32, 72, 86, 87
Receptacle—Glossary 123
References 126
Remote control 18, 54, 81, 84, 109, 110
Repairs 3
Research instrument
calibration by aortic diameter 57
calibration by thermodilution 57
cardiac oxygen 60
context sensitive help 55
control 52
derived parameters display 52
derived variables card 64
describe subject 51
describe subject card 56
display layout 52
error message display 53
files downloading 54
help notations 55
help paragraphs 55
introduction 49
miscellaneous information 52
notation 49
opening display 51
Physiocal card 62
pressure-compliance diagram 58
pressure-volume diagram 58
pressure parameters display 52
remote control 54, 110
return--to--flow card 63
select A/D signal card 61
select trends card 59
setting patient data 57
status line 52
Return-to-flow—Glossary 123
Return--to--flow
Clinique 90
Research 63
Revolving store—Glossary 123
Rise time—Glossary 123
RS-232—Glossary 124
RTF calibration—Glossary 124
RTF—Glossary 123
s
Safe data storage—Data durability 111
Safety
arm cuff pressure 101
avoiding injury 18, 109, 110
electrical 101
finger cuff pressure 101
general system 102
patient 100
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Saving a configuration 25, 79
Screen layout of Interactive User’s Guide 7
Self test 45
Sensitivity—Glossary 124
Serial I/O—Glossary 124
Serial port
downloading 54, 84, 109
I/O 44, 109, 110
RS-232 54, 109, 110
selecting 22
specification 107
Service 3
SI unit system 77
Slides
available instruments 43
buttons 40
cuff application 36
cuff size 35
Finometer control 40
front panel layout 40
height sensing 39
help 34
Software License rights 5
Specification
accuracy 108
analog I/O 103
electrical 105
environmental 104
instrumental 107
mechanical 106
Sphygmomanometer 91
Square wave—Glossary 124
Standard EN 60601--1--1 109
Start display
available options 44
calibration signals 46
off--line downloading 47
selftest 45
State of servo control 102
Status line
Classico 93
Clinique 83, 87
Physiocal 88
Research 52
Suggested order of reading 6
SVR 77
Systemic vascular resistance 77
Système International d’Unités 77
t
Tab card
Derived variables 64
Describe subject 56
Help 55
Physiocal 62
RTF cal 63
Select A/D signal 61
Select trends 59
Technical support 3
Three built--in instruments 6
Time and date 75
TNO—Glossary 124
Total systemic peripheral resistance
TPR 77
Trademarks FMS 5
Trademarks Ohmeda 5
Transducer check
arm cuff 71
77
buffer pressure 67
finger cuff 70
height calibration 69
height nulling 68
overview 65
Transducer—Glossary 124
Transfer function—Glossary 124
u
Units
pressure 77
resistance 77
Unit system—CGS 77
Unit system—medical 77
Unit system—SI 77
Unloading—Glossary 125
Unpacking—The data packets
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Unpacking—The Finometer components
Upstroke 31, 87, 88
User’s Guide
button functions 7
how to browse it 7
screen layout 7
w
Warnings, cautions, protective measures
Warranty 4, 5
Waveform filtering 72
Waveform filtering—Glossary 125
Weight 106
Wesseling criteria—Glossary 125
112
z
Zeroing—Glossary 125
99
16
Colophon
Title:
Text:
Karel H Wesseling
Design:
PRAGMA ADE
Ridderstraat 27, NL - 8061 GH HASSELT, THE NETHERLANDS
Software:
Context
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Illustrations:
Allard P Wesseling
Novice Finometer operator:
Mischa R Guelen
Copyright:
Simon Stevinweg 48, NL-6827 BT ARNHEM, The Netherlands
Date:
2002.05.06

Finometer User`s Guide

Transcription

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