Estimation of arterial oxygen tension in adult subjects using a transcutaneous electrode.

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Abstract
Transcutaneous O2 tension (tcPO2) measured with a heated electrode was compared to arterial O2 tension (PaO2) in 3 groups of adult patients: group A, 20 patients with chronic respiratory disease; group B, 8 hypothermic patents studied immediately after cardiopulmonary bypass surgery; group C; 14 patients in an intensive care unit who had 35 comparisons of tcPO2 and PaO2. For group A, the relationship of the 2 methods is given by the regression equation (in mm Hg): tcPO2 = 0.88 PaO2 + 5.0 (SE = 5.2; r = 0.93; P < 0.001) and for group C tcPO2 = 0.69 PaO2 + 14.9 (SE = 12.0, r = 0.90; P < 0.001). A method of in vivo calibration using a single arterial blood sample improved the reliability of the method in group C. In the group B patients there was no correlation between tcPO2 and PaO2, even when supplementary heating was applied to the skin. Continuous monitoring can reveal large fluctuations in arterial PO2 which would be missed by the use of intermittent arterial samples. The transcutaneous electrode can be employed usefully in intensive care monitoring of adult patients and in physiological studies where repeated arterial samples would otherwise be required.