Basis of Respiratory System Mechanics

Respiratory System
13
The goal of these lectures is to discuss
basic respiratory physiology. This
lecture will introduce the topic and
discuss lung mechanics. The sections for this lecture are:
Introduction
Structure / function, gas laws, lung/chest wall relations, pressures / forces Life is a series of chemical reactions occurring in
compartmentalized environments.
Lungs mechanics
Ventilation, complience, capacities, pressures
Alveolar gas pressures, ventilation, blood flow
Gas exchange in tissues
Physiology, the study of how life works, is based on
the simultaneous occurrence of the following three
concepts:
levels of organization
structure / function relationship
homeostatic regulation
PCO2
PO2
pH
Pa
The main purpose of life is to keep itself alive
neural CV center
inputs
cardio +
cardio -
output
vasoconstriction
chemo & baroreceptors
extrinsic
heart
periphery
(local control)
baroreceptor mechanism
(e.g. carotid sinus)
intrinsic
lung
(local control)
where we would like to be at the end
of the cardiovascular and respiratory
sections, by the end of this week
1
Respiratory System
Introduction, today lecture
Structure / function, gas laws, lungs /
chest wall relations, pressures / forces
Lung mechanics, today lecture
Transport of O2, CO2 and H ions in blood, next lecture
Hemoglobin (Hb), effect of PO2 on Hb saturation
Blood PCO2, H+ conc, t°C, DPG on Hb saturation
Carbamino compounds and carbonic anhydrase
Total blood carbon dioxide and the Haldane effect
Ventilation, inspiration / expiration,
complience / resitance
Lung volume /capacities, alveolar
ventilation / dead space
Partial pressures of gases and their
diffusion in liquids
Alveolar gas pressures and alveolar blood exchange
Matching alveolar ventilation and
alveolar blood flow
Respiratory acidosis and respiratory alkalosis
Control of respiration, next lecture
Neural generation of rhythmical breathing
Control of ventilation by PO2, PCO2, and H+ conc
Control of ventilation during exercise
Other ventilatory responses
Hypoxia and non-respiratory functions of lungs, next lecture
Hypoxia and acclimatization to high altitude
Non-respiratory functions of the lungs
Gas exchange in tissues
Respiratory System
levels of
organization
structure
- function
homeostatic
regulation
2
Respiratory System
what it actually is (info from
feedback), is compared with what it
should be (info from set-point) in a …
Homeostasis, or constancy
of the internal environment,
is needed for chemical
reactions underlying life
to occur. It is maintained,
predominantly, through
negative feedback
mechanisms
S
comparator /
integrator
E
effect
error signal
amplification
effectors mechanism
integrators compare what it should be with what it actually is and generate an error signal
Respiratory System
Homeostatic
Control
central integration center
efferent
afferent
S
E
receptor
effector
negative feedback signal
integrators compare what it should be with what it actually is and generate an error signal
3
Respiratory System
Respiratory / cardiovascular
interaction
PO2
DR=PD x A x DC / D
(DC, CO2 = 20 DC, O2)
ventilatory
pump
chemoreceptors
CO=HR x SV
S
E
receptor
control of
amplitud &
frequency
CNS
baroreceptors
VA / Q
circulatory
pump
O2
content
O2
supply
V=RF x TV
venous
return
Hemoglobin
BP
blood
flow
integrators compare what it should be with what it actually is and generate an error signal
Respiratory System
S
E
receptor
integrators compare what it should be with what it actually is and generate an error signal
4
Respiratory System
NEURAL
RESPIRATORY
CENTER
AP
inspiratory
expiratory
AP
O2
O2
THORACIC
COMPONENTS
CO2
O2
CO2
DISTRIBUTION
CENTER
distribution
S
E
receptor
PCO2
pH
center
PO2
CO2
Pa
O2
inputs
CO2
METABOLIC
COMPONENTS
(all cells)
blood
related
AP
neurogenics
integrators compare what it should be with what it actually is and generate an error signal
Respiratory System
Why do we
need a
respiratory
system ???
S
E
receptor
integrators compare what it should be with what it actually is and generate an error signal
5
Respiratory System
“Functions of the Respiratory System:”
Introduction
structure / function
gas laws
lungs / chest wall relations
pressures / forces
6
Introduction
structure / function
gas laws
lungs / chest wall relations
pressures / forces
Functions of Airway Conducting Zone
Introduction
structure / function
Anatomy of respiratory zone
gas laws
lungs / chest wall relations
pressures / forces
7
Introduction
structure / function
gas laws
lungs / chest wall relations
Blood
supply
to
lungs
pressures / forces
Introduction
structure / function
gas laws
lungs / chest wall relations
pressures / forces
8
Introduction
structure / function
gas laws
lungs / chest wall relations
pressures / forces
Introduction
structure / function
gas laws
lungs / chest wall relations
pressures / forces
9
Introduction
structure / function
inspiration
expiration
gas laws
lungs / chest wall relations
pressures / forces
Introduction
structure / function
gas laws
lungs / chest wall relations
pressures / forces
10
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
(surfactant)
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
Some
important
alveolar
ventilationfacts
/ dead on
space
Pulmonary Surfactant
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
(volumes)
11
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resistance
Lung volume /capacities,
alveolar ventilation / dead
space
spirometry
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resistance
Lung volume /capacities,
alveolar ventilation / dead
space
spirometry
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
12
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resistance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
Effects
of Breathing
alveolar - blood
exchange
Alveolar
Matching alveolar ventilation
and alveolar blood flow
Patterns on
Ventilation
Gas exchange in tissues
13
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
14
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar bloodNormal
flow
Gas Pressure
Gas exchange in tissues
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
15
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Gas exchange as function of capillary length
Lung volume /capacities,
alveolar ventilation / dead
space
PO2
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
PCO2
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Effects of Various Conditions
on Alveolar Gas Pressure
Lung volume /capacities,
alveolar ventilation / dead
space
Condition
alvPO2 alvPCO2
Breathing air with low PO2
decrease
no change
Increase alveolar ventilation and
unchanged metabolism
increase
decrease
Decrease alveolar ventilation and
unchanged metabolism
decrease
increase
Increased metabolism and
unchanged alveolar ventilation
decrease
increase
Matching alveolar ventilation
and alveolar blood flow
Decreased metabolism and
unchanged alveolar ventilation
increase
decrease
Gas exchange in tissues
Proportional increase in alveolar
ventilation and metabolism
no change
no change
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
16
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
V/Q
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
Lung mechanics
Ventilation, inspiration /
expiration, complience /
resitance
Lung volume /capacities,
alveolar ventilation / dead
space
Partial pressures of gases
and their diffusion in
liquids
Alveolar gas pressures and
alveolar - blood exchange
Matching alveolar ventilation
and alveolar blood flow
Gas exchange in tissues
Fick's first law of diffusion
J= -DA dc/dx J= net rate diffusion, moles or grs per unit time A= area of the plane
dc/dx= concentration gradient across plane
D= diffusion coefficient (proportionality cte)
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