Free Flap Blood Flow Evaluated Using Two-Dimensional Laser Speckle Flowgraphy
Transcutaneous oxygen tension (pTcO2) varies with pAO2, circulatory parameters, skin metabolism and oxygen diffusion. The necessity to heat the skin beneath the electrode to allow transcutaneous oxygen diffusion limits the use of pTcO2 in the study of skin blood flow. The oxygen measured probably emanates from the capillaries of the superficial dermis. A large number of arteriovenous shunts in the skin may modify the pTcO2 response. The heat-dilated vessels beneath the electrode behave passively in most circumstances. Differences in local blood temperature with secondary shifts in the release of oxygen from oxyhemoglobin may affect pTcO2 at high and low flow rates respectively. pTcO2 may vary with the perfusion pressure and possibly also with the resistance of the blood vessels outside the area heated by the electrode, but only at low flow rates.