358 
SURGERY AND TRANSPLANTATION 
Figure 3A & 3B. — -Photographs of inlet tubesheets taken following 4-hour perfusion. Debris on tubesheet is pri- 
marily platelet aggregates. 
relationship between surface area occluded and 
increase in pressure gradient across the oxy- 
genator. 
These data indicated that the inlet tubesheet 
of the hollow fiber oxygenator acted as a filter 
with a pore size of approximately 200 microns. 
Since this filtering action resulted in the occlu- 
sion of capillaries and consequently a decrease 
in effective surface area of the oxygenator, all 
further experiments were conducted with a da- 
cron mesh filter placed in the line on the inlet 
side of the oxygenator. Because of the occasional 
platelet aggregates noted on the outlet tube- 
sheet, a filter was also placed in the outlet 
lines to insure patient safety. 
In the second group of animals subjected to 
four hours of total cardiopulmonary bypass 
with the membrane oxygenator, filters were 
used in all ten experiments. There was no sig- 
nificant change in pressure gradient across the 
oxygenator from the beginning through the end 
of perfusion with the average final gradient 
being 105 mm Hg. Examination of the oxygena- 
tors after perfusion revealed them to be vir- 
tually free of thrombotic deposits as illustrated 
by the inlet tubesheet shown in Figure 3a. All 
animals survived the perfusion. Oxygen trans- 
fer and average results of blood gases and pH 
in the pre-operative period, at one hour of per- 
fusion, and just prior to termination of perfu- 
sion are listed in Table II. Arterial p02 re- 
mained high throughout the procedure with 
complete saturation of the effluent blood. Oxy- 
gen transfer values ranged from 207 cc/min. to 
223 cc/min. with inlet (venous) saturations 
