Prediction of Minimal Ventilation Requirements for Oxygenation in a Bubble and Membrane Blood Oxygenator During Cardiopulmonary Bypass

Abstract

2300 Optiflo II and 80 Sci-Med blood oxygenator cardiopulmonary operative records were studied to define the semilogarithmic relationship between the PaO2 and the gas-to-blood flow ratio or the percent FIO2 respectively. A mathematical model was developed to consider the linear effects of oxygenator blood residence time, temperature, hematocrit and the continuously monitored venous inlet % O2 saturation of hemoglobin on the slope and Y -intercept of the device semilog PaO2 function curve. The ventilation of five Optiflo II patient circuits (37 blood gas determinations) and five Sci-Med patient circuits (40 blood gases) ventilation was controlled by intrabypass evaluation of a mathematical statement as each of the four continuously monitored independent variables were altered. The formulae were solved to generate gas-to-blood flow ratios and FIO2’s to yield PaO2’s of 150 mmHg. The average resulting PaO2 in the Optiflo II group = 158 ± 55 mmHg (mean ± 1 S.D.), the PaO2 falling within 150 ± 60 mmHg 70.3% of the time. The average resulting PaO2 in the Sci-Med group = 180 ± 59 mmHg, the PaO2 falling within 150 ± 60 mmHg 67.5% of the time. The minimal ventilation requirements to achieve blood oxygenation were quantitated, formulated, and tested with success.