An Evaluation of the Hellige Transoxode (Servomed Oxymonitor SM 361 System): Response to Halothane and Enflurane in Vitro

The effects of halothane (0.5-2%) and enflurane (1-4%) on two Transoxode transcutaneous oxygen (TcPO₂) electrodes (Hellige Servomed Oxymonitor SM.361 system) were serially tested in atmospheres of nitrogen, air and 50% nitrous oxide in oxygen.

Both TcPO₂ electrodes reduced and “read” halothane but not enflurane. Calibration drift was significantly greater (p < 0.05) after electrode exposure to halothane; 5.40 s.e.m. 1.37 kPa vs enflurane; – 0.60 s.e.m. 0.93 kPa.

Halothane has a direct effect in rendering the Transoxode inaccurate, which is probably clinically less important than the indirect cardiovascularly medicated influence of both halothane and enflurane on TcPO₂ levels. A reduction in the electrode polarisation voltage is recommended to obviate the direct effect of halothane on Transoxode performance.