Continuous monitoring of blood PO2 in extracorporeal systems. An in vitro evaluation of a re-usable oxygen electrode.

The technique of intermittent sampling of blood during extracorporeal circulation and in vitro analysis to establish that the blood-gas status of the patient is within acceptable limits has drawbacks which may be overcome by continuous monitoring. An evaluation of an oxygen monitoring system and a comparison with a blood gas analyser have been performed. Blood of known PO2 was circulated at 15 degrees, 25 degrees and 37 degrees C in an extracorporeal system and the monitor readings and results from samples analysed on a blood gas analyser were compared with calculated partial pressures. There was no significant difference between the calculated value and the monitor readings but the blood gas analyser results were significantly lower (p less than 0.01) than the calculated values of the tonometered blood. The reasons for this difference and the potential clinical advantages of continuous monitoring are discussed.