[Transcutaneous measurement of the partial pressure of the oxygen. Theoretical bases and hemodynamic significance].

Transcutaneous measurement using a modified Clark type electrode actually measures the amount of oxygen diffusing through the skin, i.e. the transcutaneous oxygen flow (tc O2). The latter depends on arterial partial oxygen pressure, local blood flow, diffusion of oxygen in tissues and local oxygen consumption. In this study, tc O2, cutaneous blood flow (133-xenon) and pedal systolic blood pressure were measured simultaneously on the foot. In normal subjects, there was a good correlation between tc O2, perfusion pressure (r = 0.89) and local blood flow (r = 0.77). Tc O2 passively depends on perfusion pressure, because local heating induced an inhibition of vasomotricity. In patients with severe ischemia (stages 3 and 4), there was a lack of correlation between local blood flow measured by 133-xenon clearance and tc O2. This may be explained by variations of partition coefficient from patient to patient, which introduce a bias in blood flow calculation. Furthermore, tc O2 may constitute an index of nutritional blood flow, while 133-xenon clearance measures total blood flow.