Laser Doppler velocimetry vs heater power as indicators of skin perfusion during transcutaneous O2 monitoring.

Abstract

Laser Doppler velocimetry (LDV) and heater power (HP) were compared as indicators of skin perfusion during transcutaneous oxygen tension (ptcO2) monitoring in adults. The LDV probe was fitted to a Radiometer ptcO2 attachment ring, which was fixed to the forearm. ptcO2, electrode temperature, HP, and LDV measurements were recorded continuously and simultaneously. LDV was more specific and sensitive to changes in cutaneous perfusion. Moreover, changes in perfusion were signalled four to 24 times faster by LDV than by HP. Changes in ptcO2 corresponded to changes in LDV more closely than to changes in HP in all experiments. HP was more specific and sensitive to changes in electrode and air temperatures. Once hyperemia was established at 44 degrees C and the electrode heater was turned off (HP = 0), LDV measurements frequently showed persistence of hyperemia (up to 25 min). Under these circumstances ptcO2 decreased linearly with decreasing electrode temperature in the range of 44-32 degrees C. LDV performance was referenced by monitoring velocity measurements taken on a cylinder revolving at known velocities. We conclude that LDV is a useful adjunct to ptcO2 monitoring and better than HP in assessing skin blood flow. It should enhance quality control of transcutaneous O2 monitoring.