630 
PHYSIOLOGY 
Figure 1. — Schematic diagram showing instrumentation 
of conscious instrumented dogs. 
ment of our "instantaneous package", where at 
present 85% of our instrumented animals sur- 
vive for at least 5 months in good clinical condi- 
tion and with all their transducing devices func- 
tioning. Of these survivors approximately 50% 
will continue to be satisfactory for a period of 6 
months and 10-15 % will last eleven months and 
perhaps more. 
It has been only during the past year that all 
the current techniques have begun to work to 
our satisfaction and we have no idea what will 
be our ultimate survival time with satisfactorily 
functioning transducing devices. 
Our instrumentation package is designed to 
provide for recording the minimum set of pri- 
mary variables that will allow for a satisfactory 
evaluation of left ventricular performance. At 
present this requires simultaneous recordings 
of left atrial pressure, left ventricular pressure, 
aortic pressure, intrathoracic pressure, left ven- 
tricular internal diameter, left ventricular ex- 
ternal diameter, the left atrial electrogram and 
the left ventricular electrogram. These can be 
recorded continuously for periods of time vary- 
ing with the needs of the investigator. 
The conscious instrumented dogs are rou- 
tinely studied while standing quietly in a modi- 
fied Pavlov stand. The dogs are trained and are 
able to comfortably remain in the stand for as 
long as 12 hours, without becoming disturbed. 
"Hook up" time is approximately 30 minutes 
and either semicontinuous or continuous moni- 
toring is then possible. Each dog is usually mon- 
itored at least once a week and in some cases 
three times a week depending on the experi- 
mental objectives. 
Instrumentation for Measuring Pressures 
Implantable pressure transducers and small 
polyvinyl tubes are used for measuring pres- 
sures. The implantable pressure cells are made 
by Konigsberg Instruments Company.* The 
cells usually used are 6.5 mm in diameter. These 
implantable cells, with their lead wires, have re- 
mained in two dogs for as long as eleven months 
without failure. 
The implantable cells are surgically inserted 
in the locations as diagrammed in Figure 1. The 
lead wires from the cells, diameter gages, and 
electrode wires are exteriorized in the middle of 
the back of the dog's neck. The neck of the dog 
is wrapped once or twice weekly using gauze 
and "kling bandage" and a good quality adhe- 
sive tape. Each dog is checked daily to insure 
protection of these wires. 
Calibration of the implanted pressure cells is 
accomplished in the following way at present. A 
small bore polyvinyl tube is inserted into the 
ventricle, aorta and atrium along side the pres- 
sure cell. The tubing and the technique for its 
use in implantation has been described by Bar- 
ger et al.^^ These tubes are flushed daily for the 
first two weeks with a weak Heparin solution 
and then once or twice weekly. The tubes are 
brought out through the left chest wall at the 
mid-axillary line and at heart level. Pressures 
are measured again at atmospheric pressure 
using Statham P28DB strain gages, simultane- 
ously with the pressures recorded from the 
pressure cells. This is done at the start and end 
of a recording run to calibrate the pressure 
cells. The recording system is very stable and 
permits periods of recordings up to 12 hours 
without drift. Appropriate adjustments in the 
• Konigsberg Instruments Company, 2010 Foothill Boulevard, 
Pasadena, California 
