An in Vitro Assessment of a Monitor for Continuous Inline Measurement of PO 2,PCO 2 and pH during Cardiopulmonary Bypass

Abstract

The Gas STAT is a monitor which continuously measures PO₂. PCO₂ and pH inline during cardiopulmonary bypass. Using an in vitro model, the monitor's accuracy was compared to standard blood gas analysis over a range of PO₂ (2·0–66·7 kPa), PCO₂ (2·7–12·0 kPa) and pH (7–8). Its stability as affected by time, temperature, flow and haematocrit and the presence of halothane, enflurane, isoflurane and sodium nitroprusside was examined. Good correlations were found between the monitor and standard blood gas analysis for PO₂ (r = 0·999, P < 0·001) and PCO₂ (r = 0·996, P < 0·001). However, large and unpredictable systematic errors occurred. It was stable under all conditions examined, except that in one sensor there was a statistically significant decline in PCO₂ measurement with time (P < 0·005) and the PCO₂ readings were affected by temperature (P < 0·021). The monitor provides useful information for blood gas management during cardiopulmonary bypass, but should not be used without recourse to standard blood gas analysis.

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