stolic pressure, the indirect measurements
underestimated the intra-aortic measurements
from 3 to 15 mm Hg.

Pressure-Flow Dynamics

At his peak energy expenditure, which was
about 10 times that of supine rest, subject A
had a three-fold increase in the cardiac out-
put and the (a-v) oxygen difference (Table 2).
Stroke volume increased 21% and 43% above the
values recorded during supine rest and sitting,
respectively. The mean aortic pressure also
increased, but the peripheral resistance de-
creased about 50% below the value of supine
rest.

Similar changes occurred in subject B during
pared (Table 1). These direct measurements
had nearly a four-fold increase in cardiac out-
put at a peak oxygen intake nearly 12 times
that of his resting value. The peak (a-v) oxygen
difference was 2 volumes percent higher than
that recorded for subject A; the stroke volume
increased 18 and 11% above the resting and
sitting values, respectively, and peripheral
resistance also decreased approximately 50%
below the value recorded at rest.

DISCUSSION

Although the studies were limited to two
subjects, several pertinent observations were
made. A carefully monitored auscultatory sys-
tolic blood pressure will closely approximate
that value recorded by direct measurement
from the ascending aorta during rest and exer-
cise. The differences between the two techni-
ques was 6.1 mm Hg or less in ten of the twelve
experiments states studied. Only in subject B
at the two high work loads did larger dis-
crepancies appear. That greater differences
might be expected for higher work loads is not
borne out by the data for subject A or by
previous work from Henschel et al. (9). The
latter study failed to demonstrate any differ-
ences in mean pressure between the values
recorded by auscultation and by direct record-
ing (radial artery) during the maximal tread-
mill work used. Statistically significant dif-
ferences (p< .05) in mean pressure values
were observed at two lighter levels of energy
expenditure; the differences were 8 mm Hg in
each instance. Neither our data nor that of

Henschel et al. (9) compromise the value of
auscultatory systolic blood pressure measure-
ments for evaluating. cardiovascular responses
during exercise tests.

The value of auscultatory diastolic blood
pressure measurements is not well-defined. In
subject A, measurements indicated that the
cessation of sound occurred before minimal
central aorta pressure was attained. On the
other hand, the data for subject B showed that
minimal aortic pressure was reached before a
muffling of sound was detected. Henschel
et al. (9) reported discrepancies in diastolic
blood pressure values similar to those observed
in subject B. We agree with these investiga-
tors that an indirectly measured diastolic blood
pressure should be excluded from consideration
in establishing cardiovascular fitness criteria.

The observed increase in systolic blood pres-
sure with increasing energy demands is in
agreement with the findings of other investiga-
tors who recorded pressures directly, either
from an indwelling needle or a catheter in the
brachial artery. These results conflict with the
observations of Tabakin et al. (12), who failed
to record significant increases in systolic blood
pressure during heavy work.

The flow changes recorded during work in
these two subjects further substantiate the find-
ings of other investigators (5) (8) (10) that
cardiac output is augmented, not only by an
increase in pulse rate and (a-v) oxygen dif-
ference, but also by an increase in str
volume. The increase in systolic stroke volume
was less in the person who had the greatest
(a-v) oxygen difference.

ACKNOWLEDGEMENTS

The authors wish to express their gratitude
to Paul Dolan, Anita Poarch, Kamal Shanbour,
Don Rowlan and Gayla Ritter for their assist-
ance in performing these studies.

REFERENCES

1. Berliner, K., Fujiy, D. Lee, M. Yildiz, B, Garnier.
The Accuracy of Blood Pressure Determinations: A
Comparison of Direct and Indirect Measurements,
Cardiologica 37:118-128, 1960.

2. Bishop, J. M., K. W. Donald, 0. L. Wade. Circula-
tory Dynamics at Rest and on Exercise in the Hyper-
kinetic States, Clin, Sci. 14: 329,-360, 1955.

-~3-





TABLE 1

Comparison of Blood Pressures Determined Simultaneously
by Intra-Aortic Recording and Ausculation

Subject A
Experimental
Condition Systolic pressure Diastolic Pressure
Direct Direct
Recording Recording
mean + 1 SD Auscultation mean+1SD_  Auscultation
Supine Rest 140.7415 140 82.0+2.6 88
Sitting 153.7+6.4 149 95.3+4.3 100
336 mkg 159.9+8.0 165 89.7+5.9 97
1525 mkg 202.6£11.8 200 91.6+6.4 92
765 mkg 158.3+8.9 160 84.644.1 82
1220 mkg 180.5+11.3 190-180 81.6+6.6 88
Subject B
Supine Rest 132.1+2.2 126 88.8+1.7 80
Sitting 143.8+4.4 138 91.5+3,7 80
490 mkg 162.0+8.1 166 91.4+7.0 88-80
980 mkg 213.1£11.2 218 94.7463 88
1470 mkg 220.0+16.9 236-230 105.7+12.4 90-80
980 mkg 227.6£14.5 214-198 93.0+8.1 80

Tapte 1— Comparison of Blood Pressures Determined Simultaneously by Intra-Aortie Recording and Auscul-
tation.



. Fraser, R. S,, B. C. Chay

. Henderson, Y., H. W. Ha;

. Bordley, J., C.A.R. Connor, W. F. Hamilton, W. J.

Ker, C.J. Wiggers." Recommendations for ‘Human
Pressure Determinations by Sphygmomanom-
eters, Circulation 4:503-509, 1951.

. Brouha, L.. M. E.Harrington, Heart Rate and Blood

Pressure Reactions of Men and Women During and
After Muscular Exercise, Lancet 77:79-80, 1957.

Chapman, C. B., J. N. Fisher, B. J. Sproule. Be-

havior of Stroke Volume at Rest and During Exercise
in Human Beings, J. Clin, Invest. 39:1208-1213, 1960.

. Dawson, P. M. Effect of Training on Blood Pressure

in Man, Amer. J. Physiol. 50:443-479, 1920.

Studies on the Effect
of Exercise on Cardiovascular Function, Circulation
9:193-198, 1954.

| FS, Dolley. The Ef-
ficiency of the Heart, and the Significance of Rapid
and Slow Pulse Rates. Amer. J. Physiol. 82:512-524,
1927.

9.

10.

ll.

12.

13.

Henschel, A. F., F, De LaVega, H. L. Taylor, Simul-
taneous Direct and Indirect Blood Pressure Measure-
ments in Man at Rest and Work, J. Appl. Physiol.
6:506-508, 1954.

Musshoff, K. von, H. Reindell, H. Klepzig. Stroke
Volume, Arteriovenous Difference, Cardiac Output and
Physical Working Capacity and Their Relationship to
Heart Volume, Acta Cardiol. 14:427-452, 1959.

Selkert, Ewald, editor, Physiology, Little, Brown &
Co., Boston, 1963.

Tabakin, B. S., J. S. Harrison, T. W. Meriam, Jr,
and E. J. Caldwell. Hemodynamic Response of Nor-
mal Men to Graded Treadmill Exercise, J. Appl.
Physiol. 19(3) 457-464, 1964.

Wang, Y., R. J. Marshall, J. T. Shefford. The Effect
of Changes in Posture and of Graded Exercise on
Stroke Volume in Man, J. Clin. Invest. 39:1051-1060,
1960.


67-2064

Ficure 1 — Representative Intra-Aortic Pressure Tracings During Suprine Rest (left panel), Moderate Exercise
(middle panel) and Maximal Exercise, right panel).



AM 66-36

CLINICAL AVIATION MEDICINE RESEARCH:

Comparison of Simultaneous Measurements of Intra-Aortic and Auscultatory
Blood Pressures With Pressure-Flow Dynamics During Rest and Exercise

F, J. Nagle
J. Naughton
B. Balke

Approved by Released by

Kh 7, Sy PU Sege€ wo
P. V. Smart, M.D.

J. Rosert Dine, M.D.
Curer, Crvm, ArromepicaL Instircre Feperat Air Surceon

October 1966

FEDERAL AVIATION AGENCY
Office of Aviation Medicine



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During each minute of a ten-minute period
of supine rest, five minutes of sitting, and four
levels of work, the intra-aorta pressure was re-
corded and the auscultatory blood pressure was
determined from the left arm in the sequence
of systolic pressure, 15-second pulse-count and
diastolic pressure. Respiratory gas exchange
was measured from samples of air collected
during the entire 10 minutes of supine rest and
5 minutes of sitting and the last 2 minutes of
each level of “steady state” work. Inspiratory
volumes were recorded from a Tissot spir-
ometer. Blood samples for determination of
the arterial and venous oxygen content were
taken at the beginning of the final minute of
each experimental situation. Cardiac output was
calculated by the direct Fick technique (11).

Exercise on the ergometer was performed
with slight differences in procedures and se-
quences of work intensities. Subject A began
working at 366 mkg/min for a six-minute
period, continued pedalling while the intensity
was increased to 1525 mkg during the next
minute, and maintained this level of work for
six minutes. The exercise was stopped, and
he sat, recovering, on the bicycle for five min-
utes. Two additional levels of work were per-
formed continuously, for six minutes each, at
intensities of 765 and 1220 mkg respectively.

Subject B performed four consecutive six-
minute periods of work without a rest interval
at levels of 490, 980, 1470, and 980 mkg/min
respectively. The remainder of the procedure
was the same as for subject A.

RESULTS

Systolic Blood Pressure

The directly measured systolic blood pres-
sure values (Table 1) represent the means of
the peaks of the last 30 to 40 pressure pulses
recorded in the last minute of each experimen-
tal state. The systolic pressure was higher at
each level of increased energy expenditure.
Relatively small differences were observed be-
tween the directly and indirectly measured
presssures for subject A.

In subject B, there was close agreement be-
tween the two methods of measurement during
rest, sitting and at the submaximal energy de-
mands. At the peak oxygen requirement there

was a discrepancy of 16 mm Hg between the
two methods. The variation was 12 mm Hg
when he repeated six minutes of work at
980 mkg.

Two values for systolic pressure were re-
corded for each subject during maximal work.
At these levels of work, sounds were detected
at 190 mm Hg for subject A and 236 mm Hg
for subject B which disappeared momentarily
before being heard regularly at 180 and
230 mm Hg, respectively. These observations
are supported by the variations in pressure pat-
terns recorded from the aorta, an example of
which is shown in Figure 1. At rest (left panel,
Fig. 1), the peak systolic pressures were consis-
tent from stroke-to-stroke with very little
fluctuation in the base-line of the curve. At
intermediate work loads (middle panel, Fig. 1),
peak pressures varied from 177 to 150 mm Hg,
a finding which seemed to be related to respira-
tory activity. The change in peak pressure
from stroke-to-stroke was small. In maximum
exercise (right panel, Fig. 1), the effects of the
breathing cycle are present but not as well de-
fined. Periodic changes in systolic pressure
from stroke-to-stroke of as much as 40 mm Hg
are present’ which could account for the ob-
served auscultatory phenomenon. The rapid
and sizeable stroke-to-stroke pressure changes
could be due to sudden alterations in the
rhythm of breathing and possibly due to actual
variations of the systolic stroke-volume from
beat-to-beat.

Diastolic Blood Pressure

There were greater variations between intra-
aortic and auscultatory determinations when
diastolic blood pressure recordings were com-
pared (Table 1). These direct measurements
represent the means of the tracings of the last
30 to 40 pulse patterns in the last minute of
each experimental state. The maximum dif-
ference between the two techniques never
exceeded 7.3 mm Hg in subject A. The
auscultatory determinations were higher than
the intra-aortic measurements in five of the six
experimental states. The cessation of sound
was used to identify his diastolic blood pressure
since muffling of the sound did not occur.

In subject B, in whom the muffling of sound
was ‘used as the criterion for establishing dia-

-~2-


CLINICAL AVIATION MEDICINE RESEARCH:

COMPARISON OF SIMULTANEOUS MEASUREMENTS OF
INTRA-AORTIC AND AUSCULTATORY BLOOD PRESSURES
WITH PRESSURE-FLOW DYNAMICS DURING REST AND EXERCISE®
Francis J. Nagle, D.Ed., John Naughton, M.D. and Bruno B. Balke, M.D. The Biodynamics

Branch, Civil Aeromedical Research

Institute, Oklahoma

, Oklahoma and The Department

Medicine, Neurocardiology Research Program, Venera, of Oklahoma Medical Center,

Oklahoma City,

Indirect measurements of blood pressure by
auscultation during exercise are frequently used
in making an assessment of work capacity. Such
measurements may not accurately reflect the
maximal and minimal blood pressures in the
aorta during the cardiac cycle. Bordley et al.
(3) found a discrepancy of +8 mm Hg in in-
dividual readings of the systolic and diastolic
pressures between simultaneously recorded di-
rect and indirect measurements during rest.
Berliner et al. (1) found that with auscultation
the systolic pressure was consistently lower and
the diastolic pressure higher than those values
obtained by direct measurement. He em-
phasized, however, that the errors were minor
and that the auscultatory method was a re-
liable technique if it was practiced carefully.
Henschel et al. (9) reported close approxima-
tion between auscultatory and direct pressure
recordings from the radial artery at rest, but
observed discrepancies between the two tech-
niques during light and moderate exercise.

Earlier investigators, using the auscultatory
method, have demonstrated increased systolic
pressures with increasing levels of work (4)
(6). Direct pressure measurements using
Cournand needles in either the brachial or
radial artery seem to have confirmed these ob-
servations (2, 7, 13). Recently, however,
Tabakin et al. (12) reported only minor in-
-ereases in systolic blood pressure with direct
recordings even during exercise requiring three
liters of oxygen intake.
°This work was supported in part by the PHS Research

Grant Number HE-06286-04 from ‘the National Heart
Institute.

The purpose of this investigation was to com-
pare directly measured aortic pressures with
those measured simultaneously by auscultation
of the brachial artery during various physio-
logical states ranging from rest to work intensi-
ties up to aerobic limits and to study the pat-
tern of pressure and flow dynamics during
these same conditions.

PROCEDURES

Two presumably healthy men, 40 and 57
years of age, participated in the experiments.
Each performed several control trials on a
Godart bicycle ergometer in preparation for
the actual experiment. During these trials all
of the procedures except catheterization were
done. On the day of the catheterization, the
subjects reported to the laboratory 5 hours after
eating a light breakfast. They were anti-
coagulated with 100 mg sodium heparin ad-
ministered intravenously and chest electrodes
were attached for recording a single lead elec-
trocardiogram, The subjects then reclined on
a fluoroscopy table for surgery.

Number 7 Cournand catheters were inserted
into an antecubital vein and the brachial artery
of the right arm. The arterial catheter was ad-
vanced into the ascending aorta and placed
approximately six cm. above the aortic valve.
A ligature was placed at the arteriotomy site
to stabilize the catheter. The venous catheter
was advanced into the main pulmonary artery
and was stabilized by a ligature at the site of
the venotomy. All tracings were made on an
Electronics for Medicine recorder.

-1-



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