Continuous intravascular monitoring of PO2 and PCO2. A comparativein vitro-in vivo study

Two electrodes placed at the tip of catheters forin vivo determinations of \({\text{P}}_{{\text{CO}}_{\text{2}} } \) and \({\text{P}}_{{\text{O}}_{\text{2}} } \) respectively, were tested in dogs. Results were satisfactory when compared to a highly accurate reference method, correlation coefficients were close to 1 (P < 10⁻⁹). Means of the differences were respectively −1.74 ± 1.14 torr for the \({\text{P}}_{{\text{O}}_{\text{2}} } \) probe (P < 0.01) and −1.62 ± 0.72 torr for the \({\text{P}}_{{\text{CO}}_{\text{2}} } \) sensor (P < 0.0001). While no drift was detected in the \({\text{P}}_{{\text{CO}}_{\text{2}} } \) electrode that of the \({\text{P}}_{{\text{O}}_{\text{2}} } \) was significant but negligible compared to the variability of measurements. Thus, for \({\text{P}}_{{\text{CO}}_{\text{2}} } \) values between 20 and 85 torr, and \({\text{P}}_{{\text{O}}_{\text{2}} } \) values between 20 and 140 torr,in vivo monitoring is sufficiently reliable for clinical use.