Skin pH Following High Voltage Pulsed Galvanic Stimulation

Skin pH Following High Voltage Pulsed Galvanic
Stimulation
Roberta A Newton and Terence C Karselis
PHYS THER. 1983; 63:1593-1596.
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Skin pH Following High Voltage
Pulsed Galvanic Stimulation
ROBERTA A. NEWTON
and TERENCE C. KARSELIS
Prolonged electrotherapeutic treatment increases the probability of skin irritation beneath the electrodes. One probable cause is acid and base formation
under the electrodes. It has been assumed that high voltage pulsed galvanic
stimulators do not produce these chemical reactions. The validity of this hypothesis was tested on 40 healthy subjects. Three groups of subjects received
stimulation with different high voltage pulsed galvanic units, and one group of
subjects served as a control group. Pretreatment and posttreatment measures
of skin pH revealed no chemical reaction under the electrodes.
Key Words: Electrotherapy, Skin.
One of the primary concerns with using electrotherapy is skin irritation caused by the polarizing
effects of a continuous or pulsed direct current. Applying such a current on the surface of the skin will
result in a migration of ions from dissociated salts.
Positively charged ions, such as sodium (Na + ), migrate to the cathode, whereas negatively charged ions,
such as chloride (Cl - ), migrate to the anode.1 The
constituent ions come from perspiration and minerals
in the water that moistens the electrodes.2 The result
is a chemical reaction: the formation of hydrochloric
acid (HC1) under the positive electrode (anode) and
formation of sodium hydroxide (NaOH) under the
negative electrode (cathode). Resulting chemical reactions can lead to localized skin irritation beneath
the electrodes. The extent to which the reactions
proceed is dependent on the total amount of current
flow per unit time. In the case of low volt therapy,
particularly iontophoresis or prolonged electrical
stimulation, skin irritation and a burn may result.3
Generally, a patient can tolerate 6 to 9 mA of direct
current delivered through 3-in by 3-in (7.62-cm X
7.62-cm) electrodes for 20 minutes of treatment.2
By definition, high voltage pulsed galvanic stimulation (HVPGS) units are devices that deliver more
than 100 V, have a microsecond pulse duration, a low
Dr. Newton is Associate Professor, Department of Physical Therapy, School of Allied Health Professions, Medical College of Virginia,
Virginia Commonwealth University, Richmond, VA 23298 (USA).
Mr. Karselis is Associate Professor, Department of Medical Technology, School of Allied Health Professions, Medical College of
Virginia, Virginia Commonwealth University, Richmond, VA 23298.
This article was submitted January 3,1983; was with the authors for
revision seven weeks; and was accepted May 27, 1983.
average current, and a twin peak waveform.4 Because
HVPGS units have a low average current, up to 1.5
mA, the amount of acid and base formed under the
electrodes should not be great.5 Although manufacturers6, 7 of HVPGS equipment state that no or negligible irritation is produced during treatment, this
postulate has not been tested nor reported in clinical
studies. The degree, if any, of skin irritation is of
clinical concern because the use of HVPGS, particularly for prolonged treatment times, has increased in
the past several years. This study was undertaken to
determine whether significant chemical reactions resulting in skin irritation occur under the active and
dispersive electrodes during a treatment of HVPGS.
One method for examining chemical changes on
the surface of the skin is to measure for pH. Blank
noted that the pH of exposed areas varied from four
to seven for healthy subjects, and the most frequently
occurring range was from 4.2 to 5.6 pH units.8 (Skin
pH varies more for women; the pH values for women
are approximately one-half pH unit higher than those
for men). Furthermore, the extensor surfaces tend to
be more alkaline than flexor surfaces. Jolly and colleagues9 noted slightly higher (alkaline) pH values in
healthy subjects than reported by Blank8 but attributed the difference to a warm, humid climate. Draize
observed that the pH of the hand was quite variable
and believed that this was caused by frequent hand
washing and application of lotions.10 Using a pH
meter with a micro-pH electrode designed to measure
small amounts of pH is a valid method for analyzing
acid and base reactions occurring on the surface of
the skin beneath the electrodes.
Volume 63 / Number 10, October 1983
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1593
Figure. A pH meter with a digital readout, reference
electrode (A), and micro-pH electrode (B).
METHOD
Instrumentation
We used a Beckman 3500 Digital pH Meter* with
a Ml-404 flat membrane micro-pH electrode† (Fig­
ure). Precision of this pH meter was ±0.01 pH units.
The reference electrode was a silver/silver-chloride
monitoring electrode.‡ Before recording, the pH
meter was calibrated with a standard buffer solu­
tion, pH 7.0 ± 0.02 at 25°C and a reference buffer
solution, pH 4.01 ± 0.01 at 25°C.11
We used three types of HVPGS units.**,††, ‡‡
Each was checked for reliability at 100 V across a
standard (10,000 Ω resistor).
Procedure
Thirty-three women and seven men, all of college
age, volunteered to participate in this study. None
of the subjects had a known dermatological dys­
function that would influence skin pH. The ventral
surface of the forearm near the elbow and the
ipsilateral lumbar region were cleaned with distilled
* Beckman Instruments Inc, 3900 River Rd, Schiller Park, IL
60176.
† Microelectrodes Inc, Londonderry, NH 03053.
‡ Medical Products Division/3M, St. Paul, MN, 55144.
** EGS, Electro Med Health Industries Inc, 6240 NE 4th Ct,
Miami, FL 33138.
†† DynaWave Model 12, Dynawave Corp, 2520 Kaneville Rd,
Geneva, IL 60134.
‡‡ DynaMax II, JA Preston Corp, 60 Page Rd, Clifton, NJ 07012.
1594
water. This procedure does not alter skin pH but
removes any surface material.10 We took pH read­
ings on three consecutive days at the same time as
a baseline measure. On the fourth day, the subject
was randomly placed in either the Control Group
or one of three HVPGS Groups. Each group had 10
subjects. The skin was cleaned with distilled water,
and pH was measured. The sponge and outer cov­
ering were removed from the active electrode. We
used the electrodes that accompanied each unit. All
active electrodes were 4 in by 4 in (10.11 cm x 10.16
cm) and the dispersive electrodes were 8 in by 10 in
(20.32 cm x 25.4 cm). A single sheet of paper towel
moistened with distilled water was placed over the
electrode (the pH of the moist towel did not differ
from the pH of the distilled water). We used paper
toweling so that the same material was placed
between the electrode and skin.
We used elastic straps to secure the active elec­
trode firmly on the ventral surface of the forearm
and the dispersive electrode firmly to the lumbar
region. Each subject in the HVPGS Groups re­
ceived a 30-minute treatment with stimulation
characteristics of 100 V, 80 to 82 Hz, and cathodal
current to the active electrodes. The Control
Group's equipment was set up in a similar fashion
but not turned on. Because these stimulation char­
acteristics could produce a sustained contraction in
most of the upper extremity musculature, the sub­
jects were told to contract and relax periodically
during treatment to avoid muscle cramping. Im­
mediately after the treatment, the pH was remeasured under both active and dispersive elec­
trodes.
Data Analysis
Pretreatment mean pH was compared across
groups and to expected values obtained from the
literature. To determine if pH values for the study
differed from those reported by Blank, confidence
intervals for the 95 percentile were constructed
about the pretreatment mean pH values from the
sample of men and women in this study.12
One-way analysis of variance (ANOVA) was used
to determine if the difference between surface pH
before and after treatment was significant at the p
= .01 level.12 An ANOVA was performed on data
from both the active and the dispersive electrodes.
RESULTS
The mean pretreatment values for each group are
found in Table 1. The confidence intervals for both
male and female subjects include the values reported
by Blank: 4.45 pH units for men and 5.15 pH units
for women for the forearm flexor surface; and 4.65
PHYSICAL THERAPY
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RESEARCH
TABLE 2
Analysis of Variance of pH Change on the Forearm
TABLE 1
Pretreatment pH Values for Each Group
Back
Forearm
s
Control
(n = 10)
HVPGS1
(n = 10)
HVPGS2
(n = 10)
HVPGS3
(n = 10)
All groups
(N - 40)
Source
S
5.17
.55
5.14
.40
4.85
.40
4.94
.39
5.05
.57
4.94
.45
5.00
.22
4.99
.37
5.01
.45
5.00
.40
Treatments
Error
(within)
Totals
a
pH units for men and 5.11 pH units for women for
lumbar region.8 The sample can be considered representative of the population surveyed by Blank (p
= .05).
No statistically significant change in skin pH on
the forearm or lumbar region occurred after a
HVPGS treatment (p < .01) (Tabs. 2 and 3).
DISCUSSION
Skin irritability caused by electrotherapy is a primary concern of clinicians.13 When irritation occurs,
either the electrode placement must be moved to
another less effective site, or treatment must be discontinued until the irritation disappears. Because the
degree of skin irritation is dependent on the total
amount of current flow per square inch of pad, several
options are available to decrease the probability of
irritation occurring as a result of acid and base formation: 1) clean the skin before and after treatment;
2) decrease the total amount of current flow per
square inch of pad by decreasing the milliamperage
using a pulsed stimulus, increasing the size of the
pads, and securing the electrode to the skin firmly
(adjustments that still allow electrotherapeutic treatment to be effective); and 3) use a unit with symmetrical biphasic waveform.
For HVPGS, the average current is low—less than
1.5 mA,5 and the pulse duration is extremely short.
Furthermore, the total area of the active pads and
dispersive pads is relatively large. As a result, the
degree to which chemical reactions occur under the
active and dispersive pads should be low. Our study
demonstrated that when a tetanic HVPGS current
was used for an average treatment time of 30 minutes,
no significant acid and base formation as measured
df
MS
F
0.70
3
.23
.78a
10.51
11.21
36
39
.29
SS
NS.
TABLE 3
Analysis of Variance of pH Change on the Back
Source
SS
df
MS
F
Treatments
Error
(within)
Totals
0.74
3
.25
1.92a
4.83
5.57
36
39
.13
a
NS.
by surface pH existed. We used maintained tetanic
current to produce a greater amount of current flow
per unit time than would be produced if we used a
lower frequency at the same intensity. In clinical
situations, a reciprocating mode of current flow is
commonly used to produce a series of muscle contractions, or a current that is subthreshold to produce
muscle contractions is used to avoid producing a
sustained contraction.
Because the procedure used to measure pH (standard pH meter and micro-pH electrode) is relatively
quick and easy, pH changes can be measured in the
clinical setting, where a variety of electrical stimulation characteristics are used. Skin pH may be altered
in some dermatological conditions or in hyperhidrosis. Changes in pH should be monitored frequently in these patients undergoing electrotherapeutic treatment, and the skin should be carefully inspected after treatment. If pH under the active or
dispersive electrode exceeds expected values, we believe treatment should be terminated.
CONCLUSION
Skin irritation that may occur with pH changes
caused by applying a HVPGS electrotherapeutic
treatment with cathodal current and pad electrodes is
negligible. In clinical cases that warrant the use of
electrical stimulation for a prolonged period of time,
or if the patient has a known dermatological condition
that alters skin pH, then HVPGS should be the
treatment of choice.
Volume 63 / Number 10, October 1983
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1595
REFERENCES
1. Seligman LS: Physiological stimulators: from electric fish to
programmable implants. IEEE Trans on Biomedical Engineering. BME-29 (4):290-294, 1982
2. Shriber WJ: A Manual of Electrotherapy. Philadelphia, PA,
Lea & Febiger, 1975, pp 128-129
3. Kahn J: Low Volt Technique. Syosset, NY, J Kahn, 1978, p
4
4. Wolf SL (ed): Electrotherapy. New York, NY, Churchill Livingstone Inc. 1981, p 7
5. Physical Therapy Symposium on Electrotherapy. L. Woodruff
(chair). Atlanta, GA, Chattanooga Corp, 1982
6. EGS Advertisement: Electro Med Health Industries Inc.
Miami, FL, 1982
7. Alon G: High Voltage Galvanic Stimulation. Chattanooga, TN,
Reprinted by Chattanooga Corp, 1981, p 1
1596
8. Blank IH: Measurement of pH of the skin surface. J Invest
Dermatol 2:67-69, 1939
9. Jolly HW, Hailey CW, Netick J: pH determinations of the skin.
J Invest Dermatol 36:305-308, 1961
10. Draize JH: The determination of the pH of the skin of man
and common laboratory animals. J Invest Dermatol 5:77-85,
1942
11. Lee Jr RJ, Connolly ML, Romanofsky LL: Integrated system
for esophageal pH monitoring. Proceedings of the 25th Annual Conf on Eng in Medicine & Biology, Washington, DC,
Alliance for Engineering in Medicine, 1974
12. Hays WL: Statistics, ed 3. New York, NY, Holt, Rinehart &
Winston, 1981, pp 343-344
13. Kahn J: Transcutaneous electrical nerve stimulation for nonunited fractures. Phys Ther 62:840-844, 1982
PHYSICAL THERAPY
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Skin pH Following High Voltage Pulsed Galvanic
Stimulation
Roberta A Newton and Terence C Karselis
PHYS THER. 1983; 63:1593-1596.
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