Correlation of hemodynamic variables with transcutaneous PO2 measurements in critically ill adult patients

Transcutaneous oxygen (PtcO2) monitoring with miniaturized heated electrodes has been shown to continuously track arterial oxygen tension (PaO2) noninvasively in stable infants. However, the correlation between the two is less marked in unstable adults, and PtcO2 appears to be additionally influenced by perfusion. The ability of PtcO2 to detect alterations in cardiac index (CI) was evaluated in 19 critically ill adult patients. The PtcO2 was found to be influenced by the PaO2, the CI, and local vascular tone, with a rapid response time to changes in these variables. All instances of improvement in PtcO2 readings were associated with improvement in PaO2 or hemodynamic status. Because of its high sensitivity, continuous noninvasive PtcO2 monitoring should allow reduction in routine PaO2 and CI determinations. However, a decrease in PtcO2 requires immediate in-depth evaluation of the patient's PaO2 and CI because of its lack of specificity.