The influence of hydrostatic pressure and contralateral cooling on capillary blood cell velocity and transcutaneous oxygen tension in fingers.

Measurement of transcutaneous oxygen tension (pTcO2) has become a rather widely used technique. The relation of pTcO2 to skin microcirculatory parameters is, however, unclear. Capillary blood cell velocity (CBV) was compared with transcutaneous oxygen tension (pTcO2) of the finger in seven volunteers on change of hydrostatic pressure and contralateral cooling. On increase in hydrostatic pressure and also with contralateral cooling CBV decreased, while pTcO2 remained unchanged. This finding can be explained by a heat-induced local vasodilation under the pTcO2 probe in spite of a general increase in vasomotor tone. During decreasing perfusion pressure CBV was unchanged, while pTcO2 fell. This shows that with reduction in driving pressure skin pO2 is lowered. Teh absence of a decrease in CBV under these circumstances may be explained by a closure of the arteriovenous shunts, with diversion of blood into the superficial nutritional capillaries. It is suggested that CBV is related to changes in skin vasomotor tone. The pTcO2 findings indicate that the skin vasculature under the isothermally heated (44 degrees C) sensor is dilated and does not respond to vasoconstrictor stimuli.