Perfusion Characteristics During Cardiopulmonary Bypass and Subsequent Changes in Alveolar-Arterial Oxygen Tension Gradients.

In 11 elective coronary artery bypass graft (CABG) recipients, changes in alveolar-arterial O2 tension difference (deltaAaDO2) from 5 minutes before to 30 minutes after cardiopulmonary bypass (CPB) ranged from -54.9 to +63.1 torr and exhibited significant linear correlation (r = 0.77, p less than 0.01) with the mean arterial perfusion pressure (MAPP) during CPB multiplied by the duration (T) of CPB divided by the body surface area (BSA) of the patient. The regression equation (deltaAaDO2 = 0.015 MAPP divided by BSA X T -50) enables estimation of the delta AaDO2 to result from a given episode of CPB. Mural edema of airways and pulmonary vasculature, developing during CPB, may be a mechanism underlying this correlation.