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Appendix


quate zero-pressure rest intervening have been
employed with ischemic impunity and minimal
discomfort to the subject. When simultaneous
measurement of both systolic and diastolic pres-
sures is required, the systolic finger cuff is placed
on one limb and the diastolic cuff on the other.
Both cuffs cannot be used on the same limb for
obvious reasons of measurement artifact and po-
tential ischemia. In actual use, the “systolic arm”
is sling-supported so that the finger used is posi-
tioned at the same level as the brachial diastolic
cuff. This is done so that both pressures are ref-
erenced to the apex level of the heart. If the
“systolic finger” is placed above or below this
level, an appropriate hydrostatic-pressure correc-
tion must be invoked. Positions below the apex
cardiac level are not recommended since the ad-
ditional hydrostatic pressure may increase
ischemic susceptibility. A matched pair of +5
psid Statham transducers were used to sense both
pressures so that both transducers could be cali-
brated simultaneously. The previously mercury-
calibrated aneroid “Tycos” gage in the SM-2 ap-
paratus was used to calibrate both transducers.

III. Results.

In order to obtain a more comprehensive reflec-
tion of cardiopulmonary-function transients, con-
comitant measurements of the electrocardiogram
(ECG), instantaneous heart rate (HR), respira-
tory rate (f), and tidal volume (Vr) have been
recorded along with the systolic and diastolic
pressures utilizing the 6-channel “Visicorder”.
The ECG electrodes are positionel suprasternally
in order to minimize skeletal muscle “noise.” The
instantaneous HR is obtained by electronic inte-
gration of the time interval between sequential
“QRS spikes.” The f and Vy are obtained by re-
cording the impedance change from a pair of
lateral electrodes located in the horizontal cardiac
plane of the thorax. When body position remains
essentially unchanged, the Vr calibration is linear
throughout the entire chest-volume range and
proportional to the height of the impedance dis-
placement. Several examples of transient physi-
ological phenomena have been recorded using this
total system in order to demonstrate its capabili-
ties. In each example, each trace is identified by
letter and described in the accompanying legend.

A. Valsalva Maneuver—During this proced-
ure, a large, single inspiration is followed by
closure of the glottis and positive intrapulmonic

pressure application by the subject. This is
shown in Figure A6, the valsalva being effected
between points X and Y. The momentary mobili-
zation of stored pulmonary blood volume causes
a phasic increase and then decrease in the HR
and systolic and diastolic pressures with appro-
priate rebound phenomena upon release of the
positive intrapulmonic pressure,

B. Mueller Maneuver—During this procedure,
a substantial expiration towards residual volume
is followed by glottis closure and negative intra-
pulmonic pressure application by the subject.
This is shown in Figure A7, the mueller being
effected between points X and Y. The phasic HR
and pressure changes again follow as a conse-
quence of the concomitant flux in pulmonary
blood volumue. The rebound raise in HR im-
mediately following the cessation of negative
intrapulmonic pressure application is somewhat
spectacular.

C. Hyperventilation—During this procedure,
nine rather large Vz’s were invoked in rapid se-
quence by the subject. This is shown in Figure
A8, the hyperventilation occurring between X
and Y. During the hyperventilation, a sharp rise
and increase in phase swings is manifested by the
HR concomitant with a continuous drop in dia-
stolic pressure. The systolic pressure was rela-
tively unaffected by this maneuver. Upon cessa-
tion of the hyperventilation, there occurs a com-
pensatory rebound rise in diastolic pressure and
an even further rise in HR.

D. Orthostatic Stress—For this procedure
(Figure A9), the resting subject lies supine on a
tilt table and at point X, the table is tilted to a
45° feet-downward position. The table is re-
turned to horizontal at point Y. The classical
slow rises in both HR and diastolic pressure are
readily manifested during the tilt period. The
shift in the end expiratory baseline at tilt reflects
an. overall change in baseline impedance due to
downward visceral displacement.

E. Bicycle Ergometry—This procedure was
primarily used to test the artifactual suscepti-
bility of the blood-pressure devices to body move-
ment. The subject sat at rest in an upright posi-
tion on a bicycle ergometer until signalled to
commence pedalling at a rate of 60 cycles per
minute and against a constant friction of 50
watts. The “systolic arm” was sling-supported
at the apex heart level. This record is shown in





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Appendix


APPENDIX

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Figure A10. The onset of exercise is marked on
the record as point X. The two large remarka-
ble phasic swings in HR just preceding point
X coincided with the subject’s comfort adjust-
ment in preparation to commence pedalling. The
widening of pulse pressure (increasing systolic
and decreasing diastolic pressures), increasing
HR, f, and Vy as the exercise progressed are all
classical physiological responses. This record
demonstrates that body movements during er-
gometry of this type are tolerated quite well by
the blood-pressure systems as well as the others
concomitantly measured.

Treadmill ergometry was attempted after the
bicycle test, and the resultant “body bounce” of
walking caused artifactual pulse sensing by the
systolic-pressure system, thereby negating its
value as a true measure of systolic pressure under
this particular condition. A double-signal pulse
sensor is presently being explored as a possible
solution to this type of body-bounce artifact. The
diastolic-pressure system was not adversely af-
fected by treadmill walking, and hence its meas-
urements were deemed valid.

F. Rapid Decompression—The combined car-
diopulmonary assay system was tested for its
capability of measuring physiological dynamics
during a rapid decompression of a subject from
8,000 to 40,000 feet. The subject remained in an
upright, seated position throughout this proced-
ure. The subject was not denitrogenated before
the decompression. At decompression, the sub-

ject was without a mask, and, at an appropriate
altitude-synchronized signal, he proceeded to don
the mask, which consequently remained on with
a positive-pressure source of 100% oxygen for
the remainder of the test procedure. The left
arm, on which the “systolic-finger” device was
mounted, remained resting on the “arm” of the
seat. The “systolic finger” was kept at the apex
cardiac level during the whole procedure. The
right forearm, the hand of which donned the
mask, was at all other times resting in a quiet
position in the lap of the subject. The record
obtained is shown in Figure All. The letter X
denotes the onset of rapid decompression. The
mask was donned at point Y, and the chamber
altitude of 40,000 feet was attained at point Z.
The altitude for the remainder of the record re-
mained at 40,000 feet. With the exception of the
momentary disruption of the diastolic-pressure
measurement at point Y (during mask donning),
all systems funtioned satisfactorily. The sharp
rise in systolic and diastolic pressures just at the
onset of decompression, followed by a gradual
fall in both pressures until attainment of 40,000
feet is unique. The dramatic rise in HR just
prior to mask donning and its consequent sus-
tained level is remarkable as is the concomitant
increase in both f and V+. This total system has
already been used to measure two experimental
series of rapid decompression experiments, The
results of these decompression studies will ap-
pear in a consequent publication.

REFERENCES

1. Kroexer, E. J., and Woop, E. H.: Comparison of sim-
utaneously recorded central and peripheral arterial
pressure pulses during rest, exercise and tilted posi-
tion in man. Cire, Res. 3 :623, 1955.

2. O'DosnetL, T. V., and McItzoy, M. B.: The circulatory
effects of squatting. Am. Heart Jour. 64:347, 1962.

3. Henscuet, A. F., DeLaVeca, F., and Taytor, H. L.:
Simultaneous direct and indirect blood pressure meas-
urements in man at rest and work. J. Appl. Physiol.
6 :506, 1954.

4, Tapaxin, B. S., Harrison, J. S., Mentam, T. W. Jp,
and Catpwett, E. J.: Hemodynamic response of nor-
mal men to graded treadmill exercise. J. Appl. Physiol.
19:457, 1964,

5, Kororxov, N, S.: On methods of studying blood pres-
sure. Izv. Voennomed, Akad. 11 :365, 1905.

6. Borptey, J., Connor, C. A. R., Hamirton, W. F., KERR,
W. J., and Wrearr, C. J.: Recommendations for blood
pressure determinations by sphygmomanameters. Cire.
4:508, 1951.


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Appendix



AM-66-16

THE AEROMEDICAL ASSESSMENT OF HUMAN SYSTOLIC
AND DIASTOLIC BLOOD-PRESSURE TRANSIENTS
WITHOUT DIRECT ARTERIAL PUNCTURE

Michael T. Lategola, Ph.D
Hiley Harrison
Charles Barnard

Approved by Released by
ithe [USdge€ 0
J. Rosert Ditz, M.D. P. V. Srecer, M.D.

Curer, Crvin Azromepican Institute Feperat Arr Surgeon

May 1966

FEDERAL AVIATION AGENCY
Office of Aviation Medicine



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Appendix


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Appendix



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Appendix


IL. Procedure.

A suitable compromise system was devised. It
consists of two commercially available appara-
tuses used in a novel manner. For the intended
purpose, one device was extensively modified,
while the other was used essentially as originally
designed.

A. Diastolic Blood Pressure——This pressure
was measured utilizing a modification of an exist-
ing automatic blood-pressure apparatus.* Its
normal operation was the automatic sensing and
recording of auscultative diastolic and systolic
pressures (in that order) from a brachial cuff.
The qualitative operational pattern of this system
is shown in Figure A8. This particular appara-
tus was designed (with preset switches) to meas-
ure both pressures at three optional rates: once
per minute, once per 3 minutes and once per 6
minutes. The cycle, as shown in Figure A3, could
also be manually invoked to repeat as many as
four times per minute. However, this was still
far below the measurement rate needed for our
purposes. Furthermore, if cycled at four per
minute for several minutes, the relatively high
cuff pressure which would exist for the major por-
tion of the measuring time would be detrimental
to the circulation of that portion of the arm distal
to the pressure cuff. Edema and severe ischemic
discomfort would rapidly ensue.

Since another apparatus that could measure the
systolic pressure rapidly and virtually continu-
ously (to be described consequently) already ex-
isted, the Systems Research Labs. apparatus was
modified to cycle the measurement of diastolic
pressure only. With reference to the cycle pat-
tern shown in Figure A3, this was achieved
mainly by “chopping off” the systolic portion of
the cycle at point C, at which point, the coinci-
dence of a sensed pressure pulse with the first
appearance of Korotkov sounds (diastolic blood
pressure) activates a relay for rapid deflation of
the cuff. The cycle is reactivated by a preset
pressure-sensitive relay when the cuff pressure
during rapid deflation falls to a value of 10 mm
Hg. This cycle-reactivation pressure is low
enough to allow the maintenance of noncongestive,
venous blood-flow levels in the arm distal is en-
cuff. The cuff-pressure-sensing transducer is en-
ergized continuously so that the whole pressure
cycle is sensed and then recorded by a readout.

* Systems Research Labs., Inc., Dayton, Ohio.

device.** Visualization of the whole pressure
cycle allows the investigator to make favorable
momentary readjustments of cuff inflation and
deflation rates to attain the maximum number of
determinations per minute. In such a pattern,
as shown in Figure A4, the highest pressure at-
tained before the onset of rapid cuff deflation is
the system’s measurement of diastolic pressure.
Utilizing this modified system, the diastolic pres-
sure has been measured from 10 to 34 times per
minute for protracted time periods without
ischemic discomfort to the subject. The average
confidence level of this type of diastolic pressure
measurement, as judged by the cuff-pressure rise
between consecutive pulse beats, is +8 mm Hg.
This confidence level varies directly with the rate
of the slow-inflation portion of the cycle.

B. Systolic Blood Pressure.—This pressure was
measured utilizing an SM-2 continuous systolic
blood-pressure monitor. This system operates
as follows: as shown in Figure A5, a miniature
pressure cuff is positioned on the finger near its
base (A) and an SM-2 crystal pressure sensor
(B) immediately distal to the cuff to sense pulse
pressure. Arterial pulsations sensed by the crys-
tal pickup activate stepwise inflation of the cuff
to a pressure exceeding the momentary systolic
pressure. A slower, continuous, cuff-pressure
“bleed” then allows deflation of the cuff until the
sensed appearance of the first pulse to escape the
pressure restriction of the cuff. This sensed pulse
reactivates the stepwise cuff inflation. The point
at which the deflation is reversed is a measure
of systolic pressure. An example of the resulting
pattern of measurement is shown in Figure A4.
The magnitude of each step-inflation of cuff
pressure can be controlled by presetting the infla-
tion solenoid aperture. The cuff-pressure “bleed”
rate has a similar control. In this fashion, up-
wards of 20 determinations per minute are rou-
tinely possible. Because of the ischemic risk of
such high sustained cuff pressures, continuous
measurement for more than 5 minutes is inad-
visable. For the recording of long-duration,
steady-state procedures, a zero-pressure rest of
10 seconds per minute is sufficient to deter any
appreciable digital ischemia. Several 5 minute
periods of continuous measurement, with ade-

**A Heiland, 6-channel, 914 B “Visicorder”.

; Spinco Division, Beckman Instruments, Inc., Palo Alto, Call-
fornia.


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138

Appendix



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15

Appendix



THE AEROMEDICAL ASSESSMENT OF HUMAN SYSTOLIC AND
DIASTOLIC BLOOD-PRESSURE TRANSIENTS WITHOUT
DIRECT ARTERIAL PUNCTURE

I. Introduction.

In civil aeromedical research, there are sev-
eral experimental areas in which the continu-
ous measurement of systolic and diastolic blood-
pressure transients would be of immense value.
Some of these potential areas of study are: (1)
rapid decompression of aircrew and passengers
for the delineation of critical minimum-oxygen-
pressure levels and for oxygen-mask testing, (2)
dynamic assessment of changing work levels re-
lated to optimal aircrew and air traffic controller
performance, and (8) assessment of cardiopul-
monary transients in pilots during stressful and
fatiguing flight maneuvers.

One possible method of obtaining beat-to-beat
blood pressure measurements is shown in Figure
Al. (All Figures, Al through A11, are in the
Appendix.) This figure reveals an assessment as
obtained by direct systemic arterial puncture
in an anesthetized dog. The high and low points
of each pressure wave represent the momentary
systolic and diastolic blood pressures, respectively.
Although this procedure is routinely used in ani-
mals, and occasionally in humans, the con-
traindications for general human use are many
and severe. Despite local anesthesia, arterial
puncture is painful and will hence militate
against the attainment of “normal” baseline pres-
sures. The danger of sepsis, blood-clotting and
damage to the aterial intima are always present.
It is for these main reasons that human experi-
mental protocols have relied heavily on the in-
direct measurement of blood pressures. In
“steady-state” experiments, the auscultative,
blood-pressure-cuff method has been used success-
fully® °, Utilizing this method, the assessment
of systolic blood pressure can be obtained with
an average accuracy of +2 mm Hg. Since the
the diastolic blood-pressure measurement depends
on subjective audial judgment of the proper “fall-

off” of arterial Korotkov sounds, the measure-
ure accuracy of this parameter is in the
order of +5 mm Hg. In recent years, this
situation has been improved by the appearance of
automatically recording, auscultative, blood-pres-
sure devices which have substituted on objective
microphone for the ear of the investigator. This
type of device has improved the accuracy of both
systolic and diastolic blood pressure assessments

- in the steady-state. When automatically cycled,

however, this apparatus, at best, can yield only
two reasonably accurate determinations of both
systolic and diastolic pressures per minute. An
example of this type of recorded measurement is
shown in Figure 2.* The vertical oscillations su-
perimposed on the pressure tracing emanate from
the microphone in the brachial blood-pressure
cuff. The oscillation amplitude is proportional
to the volume of the Korotkov sounds. During
the pressure deflation cycle, the first audio oscilla-
tion marks the value of the systolic blood pres-
sure. The diastolic blood pressure is marked by
the first audio oscillation which is less than one-
third of the preceeding maximum audio oscilla-
tion occurring during the entire deflation period.
Each pressure determination has an accuracy of
++ one-half the average pressure drop between
each sequential pair of audio oscillations. There-
fore, it should be obvious that in order to obtain
more than two of these complete cycles per min-
ute, the deflation “pressure-bleed” rate would
have to be inereased, thereby increasing the inter
audio-oscillation pressure drop and hence decreas-
ing the accuracy of each pressure determination.
Because of this accuracy limitation and the re-
quirement to increase the frequency of the pres-
sure determinations to assay short-duration tran-
sient phenomena, a search was instituted for a
compromise system that would fulfill this need
without resort to direct arterial puncture.

* “Physiograph” recorder—E&M Instrument Co., Houston, Texas.



Qualified requestors may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientific and
Tecnical Information, U.S. Dept. of Commerce, Springfield, Va. 22151


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Appendix