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

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 PaO2 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.