The response of blood flow velocity in finger nailfold capillaries to contralateral cooling.

The present study was performed in order to determine the effect of contralateral cooling on capillary blood flow velocity (CBV) in human nailfold capillaries during rest and postocclusive reactive hyperemia. The following reactions were found: Mean resting CBV (2 min) was slightly (19%) but not significantly (p greater than 0.05) decreased by cooling of the contralateral hand. However, immediately after the hand was submerged in the cold water (15 +/- 1 degree C) there was a short (3-10 S) but marked decrease of CBV. In 3 of 7 subjects CBV stopped completely for 5-10 S. No change of the skin temperature was seen during the contralateral cooling procedure. There was an increase in periodic and intermittent flow fluctuations of CBV during contralateral cooling, which was not noticed in the digital pulse amplitude (DAPA), indicating a reflex-mediated vasoconstriction at the microcirculatory level. The peak CBV during postocclusive reactive hyperemia (PRH) response was not influenced by contralateral cooling (1.01 +/- 0.57 mm/s before and 0.98 +/- 0.4 mm/s after cooling). However, because of the decrease in mean resting CBV during contralateral cooling, the percent increase in CBV during PRH increased from 66% to 104% by the cooling procedure (p greater than 0.05).