In vivo calibration of flow-dependent blood gas catheters.

In vivo calibration of blood gas catheters is complicated by the fact that their signals are flow dependent. A calibration method is described here, which permits continuous in vivo calibration. The principle is to compensate for flow dependence through simultaneous measurement on an inspired, inert reference gas of known partial pressure. The method is demonstrated by experiments on three anesthetized dogs, in which the arterial oxygen partial pressure was measured in situ with a flow-dependent blood gas catheter. The compensated signal was in good agreement with the partial pressure of oxygen measured with conventional techniques.