FRANKLIN, VATNER, HIGGINS, PATRICK, KEMPER AND VAN CITTERS 
1129 
situation enables the study of circulatory phys- 
iology in untethered, conscious baboons as they 
undergo a variety of spontaneous activities in- 
cluding eating, fighting, sleeping and postural 
changes (Figure 4). Studies to this date in con- 
scious baboons have been primarily descriptive. 
For instance, we have studied the normal varia- 
tions that occur in coronary dynamics in con- 
scious baboons-'' and we have described the 
regional circulatory adjustments that occur in 
response to eating and digestion.-" A natural 
extension of these studies, and those involving 
the response to severe exertion in dogs, will in- 
volve the study of the central and peripheral 
circulatory control mechanisms that are utilized 
in a variety of cardiovascular stressful situa- 
tions in a primate model of man, e.g., the 
baboon. 
The system described in this paper can meas- 
ure ventricular and arterial pressures, regional 
blood flow^s, and ventricular and aortic dimen- 
sions. Pressure is measured using a miniature 
! pressure gauge chronically implanted w^ithin 
the ventricular chambers or within the lumen of 
the aorta. Dimensions are measured by record- 
ing the transit time of bursts of sound travelling 
between piezoelectric crystals sutured in opposi- 
tion across the ventricle or aorta. Flows are 
measured using the ultrasonic Doppler shift 
blood flowmeter, i.e., measuring the Doppler 
shift in 10 MHz sound backscattered from the 
moving erythrocytes. Each of the electrical sig- 
nals is converted to a frequency modulated sub- 
carrier signal. These signals are impressed on 
a VHF FM carrier which is transmitted from 
the animal to the remote receiver and demod- 
ulators. The system electronics and power sup- 
plies are sufficiently small to be carried in a 
backpack by the animal, and sufficiently stable 
to allow measurements to be taken over periods 
of weeks. 
Techniques for radiotelemetry of cardiovas- 
cular variables have been developed and applied 
to a variety of physiological studies. These tech- 
niques have enabled the study of animals living 
in habitat,^^ the elucidation of circulatory con- 
trol mechanisms utilized during near maximal 
exercise and the use of larger primates as cir- 
culatory models of man. 
REFERENCES 
1. Patrick, T., Vatner, S. F., and Franklin, D. A 
system for radiotelemetry of left ventricular di- 
ameter and pressure in untethered animals. Proc. 
of the 24th ACEMB: 13:315, 1971. 
2. Franklin, D., Vatner, S. F., Higgins, C. B., Pat- 
rick, T., Kemper, W. S., and Van Citters, R. L. 
Measurement and radiotelemetry of cardiovascular 
variables in conscious animals: Techniques. Proc. 
of Nat'l. Conf. in Res. Animals in Med., Washing- 
ton, D.C. 1972. 
3. Van Citters, R. L., and Franklin, D. L. Telem- 
etry of blood pressure in free-ranging animals via 
an intravascular gauge. J. Appl. Physiol. 21:1633, 
1966. 
4. Franklin, D. L., Watson, N. W., Pierson, K. E., 
and Van Citters, R. L. A technique for radiotelem- 
etry of blood flow velocity from unrestrained ani- 
mals. Amer. J. Med. Electronics, 5:24, 1966. 
5. Vatner, S. F., Franklin, D., and Van Citters, 
R. L. Simultaneous comparison and calibration of 
the Doppler and electromagnetic flowmeters. J. 
Appl. Physiol. 29:907, 1970. 
6. Van Citters, R. L., and Franklin, D. Radio 
Telemetry techniques for study of cardiovascular 
dynamics in ambulatory primates. Ann. N.Y. Acad. 
Sci. 162:137, 1969. 
7. Vatner, S. F., Higgins, C. B., White, S., Patrick, 
T., and Franklin, D. The peripheral vascular re- 
sponse to severe exercise in untethered dogs before 
and after complete heart block. J. Clin. Invest. 
50:1950, 1971. 
8. RusHMER, R. F. Constancy of stroke volume during 
exercise. Amer. J. Physiol. 196:745, 1959. 
9. RusHMER, R. F., Smith, 0., and Franklin, D. 
Mechanisms of cardiac control in exercise. Circ. Res. 
7:602, 1959. 
10. Vatner, S. F., Franklin, D., Higgins, C. B., Mil- 
lard, R. W., Patrick, T., and Braunwald, E. The 
left ventricular response to severe exercise in un- 
tethered dogs. (Abstract) J. Clin. Invest. 51:99a, 
1972. 
11. Chapman, C. B., Henschel, A., Minckler, J., 
Forsgren, a., and Keys, A. The effect of exercise 
on renal plasma flow in normal male subects. J. 
Clin. Invest. 27:639, 1948. 
12. White, H. L., and Rolf, D. Eff'ects of exercise and 
of some other influences on the renal circulation 
in man. Amer. J. Physiol. 152:505, 1948. 
13. Bucht, H., Ek, J., Eliasch, H., Holmgren, A., 
Josephson, B., and Werko, L. The eff"ect of exer- 
cise in the recumbent position on the renal circula- 
tion and sodium excretion in normal individuals. 
Acta Physiol. Scand. 28:95, 1953. 
