The effect of the transcutaneous electrode on the variability of dermal oxygen tension changes.

Transcutaneous oxygen measurements (TCPO2) are being used increasingly for the assessment of tissue viability in the ischaemic limb. The major objective with such a technique is to determine the critical level of TCPO2 which defines the boundary between skin viability and non-viability. To be able to do this, an assumption is made that measurements from different centres using various TCPO2 sensors are comparable. This study shows that static and dynamic changes of TCPO2 (air to oxygen breathing) made with two commercially available instruments are not directly comparable. We suggest that the physical characteristics of present TCPO2 electrodes are not optimal for measurements on adult skin. TCPO2 measurements made in conditions of skin ischaemia should be interpreted with caution because the ratio of local oxygen demand to blood flow is such that the measurement may be underestimated by TCPO2 electrodes with a high oxygen consumption.