A novel method for indirectly monitoring arterial pO₂ during cardiopulmonary bypass

Abstract

Arterial blood oxygen tension (P_aO₂) is a vital variable that has to be monitored during cardiopulmonary bypass (CPB). The aim of this study was to develop an alternative method for continuously P_aO₂ monitoring during CPB, based on measurements of exhaust-gas from an oxygenator. A total of 15 adult patients undergoing CPB (n = 81 samples) were included in a study in order to develop an appropriate algorithm for P_aO₂ estimation based on exhaust gas monitoring of the oxygen tension (P_exO₂). The acquired data was used as a basis for developing a statistical prediction algorithm designed for continuously estimating the P_aO₂-level based on exhaust gas data in combination with data from the surrounding medical equipment. A new instrument was developed in order to implement this P_aO₂ prediction algorithm and was tested on five patients (n = 39 samples). When the first sample was used for calibrating the instrument, the mean (SD) error was 8.7% (7.3%) with a 95% CI of 6.1–11.3%. Our results indicate that a pO₂-exhaust monitoring device with adequate precision is obtainable, but further studies are required.

Keywords:

• Oxygenator
• Cardiopulmonary bypass
• Oxygenator exhaust
• Monitoring
• Oxygen partial pressure