Intra-aortic oxygen distribution during veno-arterial bypass (VAB) without oxygenation in circulatory assist

Right atrium-femoral artery VAB without oxygenation was performed in 7 dogs at 3 different bypass ratios, 15% 30%, and 45%. Respiration and cardiac output were controlled. Precise intra-aortic distributions of PO2 and O2 saturation were determined by means of a PO2 catheter probe and an oxygen analyzer. The following was concluded: 1) The blood pumped from dog heart produced a narrow "mixing zone" in the mid-aorta with the blood pumped from VAB. The area of the "mixing zone" was in the distal half between renal artery and bifurcation at 15% bypass ratio, in the proximal half between renal artery and bifurcation at 30% bypass ratio, and from celiac artery to below renal artery at 45% bypass ratio. It shifted proximally as the bypass ratio increased. 2) In order to supply necessary oxygen to abdominal viscera, it is recommended that the bypass flow should not exceed 30% of the baseline cardiac output.