Transcutaneous pO2 measurement during tourniquet-induced venous occlusion using dynamic phosphorescence imaging

A sufficient oxygen supply in skin grafts requires a functioning microcirculation. Venous occlusion impairs the microcirculation and is therefore a major threat of healing. Luminescence life time imaging (LLI) enables the non-invasive and two-dimensional assessment of the transcutaneous oxygen partial pressure (p(tc)O2). In the current trial this new device was applied for monitoring of venous congestion. A tourniquet on the upper arm was inflated up to 40-50 mmHg and released after 10 min in eight healthy volunteers. The p(tc)O2 was measured at the lower arm every minute prior to, during and up to 10 min after cuff occlusion (40 degrees C applied skin temperature) using LLI of platinum(II)-octaethyl-porphyrin immobilized in a polystyrene matrix. For validation the polarographic Clark electrode technique was applied in close proximity and measurement was performed simultaneously. p(tc)O2 measurements prior to (Clark: 50.68+/-5.69 mmHg vs. LLI: 50.89+/-4.96 mmHg) and at the end of the venous congestion (Clark: 16.41+/-4.54 mmHg vs. LLI: 23.82+/-3.23 mmHg) did not differ significantly using the Clark electrode vs. LLI. At the initial congestion respectively reperfusion phase the Clark electrode measured faster decreases respectively increase of p(tc)O2 due to oxygen consumption of this method. This experimental trial demonstrates the applicability of LLI to quantify the p(tc)O2 under changing venous blood flow. The use of planar transparent sensors allows the non-invasive generation of two-dimensional maps of surface pO2 what makes this method particular suitable for monitoring of skin grafts.