A transparent transcutaneous oxygen electrode for simultaneous studies of skin capillary morphology, flow dynamics...

Transcutaneous PO2 (tcPO2) measurements have become a standard method for a monitoring arterial PO2 of patients with cardio-respiratory problems. Direct heating of a silver/silverchloride anode induces a local hyperemia of the skin, which permits measurements of PO2 on the skin surface polarographically. This technique has been applied recently to quantify skin variability in peripheral arterial occlusive disease, to predict the optimal amputation level or skin transplant survival. However, so far local capillary morphology could not be correlated to tcPO2 data. The purpose of the newly developed electrode was to abolish this disadvantage and to be able to correlate capillary morphology and distribution to local tcPO2 by means of videomicroscopy or dynamic fluorescence videomicroscopy. The middle part of the new electrode consists of a glass cylinder (diameter 4.5 mm) and only one 15 micron Platinum cathode, which provides a negligible O2-consumption of the electrode itself (approx. 5.5 x 10(-3) mmHg/min). The careful optical grinding of the glass cylinder gives a good transparency for observing the capillaries through the incident light microscope of the videomicroscopy system. The electrode is covered by a 25 micron Teflon membrane, which also constitutes no essential optical barrier. By focusing at the tip of the Platinum cathode and the adjacent capillaries the distance between both objects or the intercapillary distance can be measured. The new combined system of transcutaneous PO2 measurements and simultaneous videomicroscopy has great potential as a practical method to provide new insights into local skin oxygen supply and the local microcirculatory flow distribution and capillary morphology.