Use of the oxygen transfer slope and estimated membrane oxygen transfer to predict PaO2

Abstract

The purpose of this investigation was threefold: (1) could the perfusionist accurately estimate oxygen transfer (VO₂/minute) while on CPB; (2) could this estimate, and its position on the oxygen transfer slope (OTS), predict resultant PaO ₂ values within a specific range; and (3) could previously derived performance 'normals' be used during this study.

Fifty-four sets of samples (both arterial and venous) from 27 oxygenators were used in this study. Each oxygenator provided one normothermic and one hypothermic set of samples. In 48 of the 54 samples (88.9%) the predicted VO₂/Minute was within ± 10% of the actual VO₂/Minute. Thirty-nine of these 48 (81.25%) had resultant PaO₂ values within our target range of 140 ± 30 mmHg. The PaO₂ for these 39 samples ranged from 110 to 168 mmHg with a mean of 133 mmHg. The percentage of predicted shunt (POPS) ranged from 59.0 to 192.4% with a mean of 109.3% (SD = 23.81 %). With this degree of variability, we concluded that the perfusionist must assess VO₂/minute as well as POPS in order to predict the resultant PaO₂.