Rhythmical variations in human skin blood flow.

Rhythmical variations in human skin blood flow have been studied with laser Doppler flowmetry. In healthy adults the appearance of the rhythmical activity and its magnitude were found to differ widely between subjects, while the individual frequencies of the oscillations studied on forehead skin were close to the group average (8.6 +/- 0.7 cycles/min, mean +/- S.D.). Intraindividual variations in frequency of the blood flow rhythmicity were found in different skin regions, indicating the local nature of its control mechanism. Application of anaesthetic paste on forearm skin completely blocked the rhythmical variations in blood flow that were recorded before the experiment. Increasing frequency of the rhythmical variations in blood flow with skin temperature was demonstrated on the forehead, upper arm and forearm skin. Neither oxygen breathing nor anaesthetic block of the nerves innervating the skin region examined influenced the rhythmical variations in skin blood flow. On the basis of the results obtained, it was concluded that the oscillatory variations in skin blood flow are intimately associated with the rhythmical active vasomotion (small vessel rhythmical diameter changes) reported previously in the literature.