Effects of local convective cooling and rewarming on skin blood flow.

Local areas of the thighs, palms and fingertips of ten healthy subjects were exposed to cold (10 degrees C) and warm (40 degrees C) air flows of three different velocities, 0.25, 0.50 and 0.75 m/s. The rewarming followed immediately after the cooling. Each climatic condition was applied for 45 min. Skin blood flow and skin temperature were continuously measured by laser Doppler flowmetry and thermometry, respectively. Significant (p less than 0.01 or less) reductions in both skin blood flow and skin temperature, compared to the levels recorded in the room climate, were observed at all the test sites and for all the cooling climates. During cooling no significant differences were obtained between skin blood flow levels reached for the different air velocities, except for the palm (p less than 0.01). Rewarming by the air velocities 0.25 and 0.50 m/s could not even bring the palm skin blood flow back to the precooling levels, while the fingertip (except for the low air velocity) and the thigh showed a hyperaemic reaction. The discrepancies in response pattern between the test sites are interpreted to be due to their different microvasculature and vasomotor innervation. The relationship between skin blood flow and skin temperature was found to be exponential. The correlation coefficients were 0.84, 0.72 and 0.85 for the thigh, palm and fingertip, respectively.