MEASUREMENT AND RADIOTELEMETRY OF 
CARDIOVASCULAR VARIABLES IN CONSCIOUS ANIMALS: 
TECHNIQUES AND APPLICATIONS 
Dean Franklin, Stephen F. Vatner, Charles B. Higgins, 
Thomas Patrick, W. Scott Kemper and Robert L. Van Citters' 
Techniques : Among the primary impediments to veri- 
fication of hypotheses regarding the extent to which 
identified cardiovascular control mechanisms are brought 
into play in the normal animal is the inability to meas- 
ure the fundamental variables in the normal animal 
undergoing spontaneous activities. To this end we have 
developed techniques suitable for measurement and 
radiotelemetry of the basic hemodynamic variables in 
untethered, conscious animals. The system provides the 
capability for measurement of ventricular and arterial 
pressures, regional blood flows (coronary, mesenteric, 
renal and iliac), and of ventricular and aortic dimen- 
sions. The system adequacy has been proved in success- 
ful applications ranging from studies of cardiovascular 
dynamics in exercising sled dogs to studies of giraffes 
and baboons in habitat. 
Applications: Ideally, cardiovascular control mecha- 
nisms should be elucidated in man. Unfortunately, the 
human cardiovascular physiologist has markedly lim- 
ited access to measurement of the fundamental circula- 
tory variable on the basis that atraumatic, harmless, 
instrumentation techniques for measurement of these 
variables has not yet been developed. For these reasons 
cardiovascular physiology and pharmacology are most 
commonly studied in animal models of man. 
Accordingly, we have developed instrumentation and 
handling techniques to directly measure and radiotelem- 
eter measurements of blood flows and pressures and car- 
diac dimensions from healthy, conscious untethered ani- 
mals. We have applied these techniques to a wide 
variety of experimental situations including elucidating 
cardiovascular physiological and pharmacological con- 
trol mechanisms in conscious animals, studying coronary 
dynamics in untethered baboons, blood pressure re- 
sponses in free-ranging giraffes and regional blood flow 
distribution during severe spontaneous exercise in dogs 
unencumbci-ed by tethers, treadmills and the laboratory 
environment. 
INTRODUCTION** 
A major fraction of our knowledge of human 
cardiovascular physiology is derived from ani- 
* Department of Medicine, University of California, San Diego, 
Scripps Clinic and Research Foundation, La JoUa, California, 92037, 
and University of Washington, Seattle, Washington. 
** Supported in part by U. S. Public Health Service Grant Nos. 
HL 12373 and HL 13441. 
mal models with the assumption that knowledge 
so derived is applicable to humans. For example, 
a basic cardiovascular control mechanism identi- 
fied by experiments in dogs is assumed to have 
its counterpart in the human cardiovascular 
system. Indeed, it is rare when results from 
animal experiments are totally inapplicable to 
humans. However, most commonly such experi- 
ments are conducted using anesthetized animals 
or excised tissue. While such experiments reveal 
mechanisms by which the cardiovascular sys- 
tem is controlled, they do not confirm the extent 
to which so identified mechanisms are drawn 
into play in the intact, unanesthetized mammal. 
For example, a potent neural mechanism ca- 
pable of reducing kidney blood flow to zero, has 
been repeatedly identified in anesthetized ani- 
mal preparations. This mechanism traditionally 
has been believed to reduce blood flow to the 
kidney during conditions of stress such as ex- 
treme exercise in the normal animal, i.e., blood 
flow was thought to be shunted from the kidney 
to provide a part of the additional flow re- 
quired by the exercising muscle. Recent work 
using direct measurements of renal blood flow 
during extreme exercise in dogs has demon- 
strated that flow to the kidney does not decrease 
during exercise except under the most unusual 
(and probably pathological) circumstances. 
It is clear that hypotheses regarding cardio- 
vascular function and control must be ultimately 
tested in normal, conscious animals with all con- 
trol mechanisms intact and under as nearly nor- 
mal conditions as possible. To this end we have 
developed an instrumentation system suitable 
for measurement and radiotelemetry of funda- 
mental cardiovascular mechanical variables in 
animals undergoing spontaneous activities. The 
three variables used to describe gross hemo- 
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