A METHOD TO STUDY THE REGULATION OF CORONARY FLOW 
AND OF OTHER CARDIOVASCULAR FUNCTIONS IN THE 
UNANESTHETIZED PERFORMING DOG 
Walter Ehrlich, Julij G. Tosheff, Paolo Caldini, David Krausman, Francine Schrijen and Joseph V. Brady* 
A method is described for studjring the regulation of 
coronary flow in the unanesthetized dog during the 
transition from rest to various standardized activities in 
a controlled environment. Flows in the circumflex 
branch of the left coronary artery and in the ascending 
aorta are recorded continuously. They are also inte- 
grated for each heart cycle and for each consecutive 
two-second interval. Systolic and diastolic blood pres- 
sure in the aorta, right atrial pressure, pleural pressure, 
and heart rate (beat-by-beat) are recorded simultane- 
ously. The implantation of the sensors, the recording 
technique, the preprocessing for the computer analysis, 
and the statistical evaluation are described. 
INTRODUCTION 
Our laboratory tries to enhance today's un- 
derstanding of the regulation of the systemic 
circulation, and especially of the coronary flow 
by studying the changes of circulatory func- 
tions during the transition from the steady 
state of rest to the steady states of various ac- 
tivities. We are interested in the direction, the 
extent, and the time sequence of the dynamic 
changes. The circulatory functions are, there- 
fore, recorded continuously and evaluated in 
consecutive two-second intervals. 
ANIMAL PREPARATION 
Dogs are trained to stand still, to run, to eat, 
to drink or to perform other simple behavioral 
tasks in the experimental environment. When 
this training is completed, the animals are oper- 
ated upon. All sensors to be implanted are gas 
sterilized. The operating table is covered with 
ultraviolet radiation.^ The requirements of 
asepsis are strictly observed. The animals are 
narcotized (Barbithesal 650-800 mg. i.v.), intu- 
bated, respirated with a Harvard pump, and 
* Laboratory of Behavioral Cardiodynamics, Department of Psy- 
chiatry and Behavioral Sciences, School of Medicine; Department of 
Environmental Medicine, School of Hygiene and Public Health, The 
Johns Hopkins University, Baltimore, Maryland 21205. 
thoracotomized in the left fifth intercostal 
space (Figure 1). A flow transducer is im- 
planted on the circumflex branch of the left cor- 
onary artery, and an occlusion cuff, as described 
by Gregg et al.,^ is placed downstream from the 
transducer. Another flow transducer is attached 
to the ascending aorta. A 15 gauge polyvinyl 
chloride catheter is introduced into the right 
atrium through the left external jugular vein. 
An 18 gauge polyvinyl chloride catheter is in- 
serted via the left carotid artery into the aorta 
with the tip of the catheter close to the aortic 
valve. A valve developed to measure pleural 
pressure changes^ is fixed to the thoracic wall, 
and a 15 gauge polyvinyl catheter is slipped 
over the tube penetrating through the sixth in- 
tercostal space. The chest is closed. Air and 
fluid are evacuated through a rubber tube by in- 
flating the lungs. The tube is then removed. The 
distal end of the catheters as well as the connec- 
tors of the flow transducers are brought out 
through the dog's back. When the dog is not in 
Figure 1. — Schema of preparation. 
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