Transcutaneous hydrogen clearance--a new non-invasive technique for assessing blood flow in human skin

A new technique for the non-invasive assessment of skin blood flow is described using a modified, commercially available transcutaneous oxygen electrode. Initially, experiments were carried out on normal volunteers at skin temperatures of 40 degrees C and 44 degrees C. Transcutaneous H2 (tcpH2) clearances were measured after the subject had breathed a mixture of 2% H2 in air until a saturation value in the skin had been reached. tcpH2 clearance results were compared with laser Doppler flux values measured simultaneously on adjacent sites and at the same temperatures under control and reactive hyperaemic conditions. Good reproducibility for the tcpH2 technique and significant correlation (p < 0.002) between it and laser Doppler flux values at the same temperatures was demonstrated. In further experiments, (I125) 4-iodoantipyrine clearances (IAP) were carried out immediately prior to and at the same sites as tcpH2 clearances in critically ischaemic lower limbs. The correlation between the methods and the differences between tcpH2 values observed in normal and critically ischaemic skin were highly significant (p < 0.002).