[Intra-arterial catheter oximetry and pulse oximetry in comparison with CO-oximetry in heart surgery]

Abstract

This study evaluates the measurement of oxygen saturation by arterial catheter oximetry and pulse oximetry. The values are compared to values obtained by CO-oximetry. METHODS. In eight patients undergoing cardiac surgery, we determined the oxygen saturation of arterial and mixed-venous blood by CO-oximetry (IL 282, Instrumentation Lab) at prospectively defined points of measurement before, during, and after extracorporeal circulation. At the same points of measurement, saturation readings obtained by arterial catheter oximetry (U425C, Abbott) and pulse oximetry (Siemens/Nellcor) were recorded. RESULTS. The mean saturation values determined by both catheter oximetry and pulse oximetry differed from the mean values obtained by CO-oximetry by less than 1% (= bias). The standard deviations of the readings in relation to readings of CO-oximetry (= precision) were +/- 0.5% to +/- 1.0% for catheter oximetry and +/- 1.0% to +/- 1.3% for pulse oximetry. Furthermore, it was possible to obtain saturation readings in 99%-100% of measurements by catheter oximetry; in contrast, this was possible by pulse oximetry in only 59%-84% of measurements. Low mixed-venous saturation values were not indicated by any of the arterial methods of measurement. CONCLUSIONS. Catheter oximetry was superior to pulse oximetry with regard to both precision of saturation values and reliability to obtain values. Invasiveness and high costs are disadvantages of catheter oximetry, but if reliable and exact measurements are important at any time during surgery or intensive therapy, intra-arterial catheter oximetry is preferable to pulse oximetry.