Transcutaneous Oxygen Measurement in Adult Intensive Care

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Abstract
Transcutaneous O2 [PtcO2] gives by a noninvasive technique continuous information about central PO2 [O2 partial pressure]. Consecutive PtcO2 measurements are reported in 15 adult patients, all with indwelling arterial catheters. Of the patients, 13 were artificially ventilated, 5 had normal body structure and normal skin circulation, 5 were obese and had normal skin circulation and 5 were hypothermic with a normal heart frequency or slight bradycardia. The radiometer equipment TCM1 was used. The electrode surface temperature was 45.0.degree. C (.+-. 0.2.degree. C). The O2 concentration in the inspired air was altered several times for all patients, and arterial samples were drawn at a stable PtcO2 level. On average, 7 samples were drawn from each patient. The correlation between PtcO2 and PaO2 was highly significant in 4/5 patients in both the obese patient group and the normal patient group. In the hypothermic patient group the correlation between PtcO2 and PaO2 was highly statistically significant in 2/5 patients. The regression line between PtcO2 and PaO2 was calculated for each patient, and a mean regression line was obtained for each group. The regression line in the obese patient group was displaced to the right and parallel to the regression line in the normal patient group; the regression line in the hypothermic patient group was less sloping and showed a higher intercept. The PtcO2 monitoring technique reliably reflects changes in the central oxygenation of adult intensive care patients. In some patients with decreased skin circulation, the relationship between PtcO2 and PaO2 seemed to be constant for the same patient, yielding statistically significant correlations. This study cannot determine whether this would be true in all clinical situations; the relationship between PtcO2 and PaO2 should be checked frequently when measurements are performed in patients with decreased skin circulation. Using PtcO2 monitoring method in patients near death showed that the reliability of the method decreases with decreased skin circulation.