Active and passive modulation of cutaneous red cell flux as measured by laser Doppler anemometry.

1) We have found that the fluctuations in blood motion and blood content in cutaneous microvessels in man can be related to either active vasomotion (an order parameter for this system) or to a passive penetration of arterial (or venous, not shown) pressure waves (the control parameters for the microvascular blood motion). Arterial, respiratory (not shown), neuronal and myogenic rhythms can be clearly differentiated. 2) Spectral analysis of the signal fluctuations of a LDA method (monitoring phasic shifts in blood velocity) in combination with a photoplethysmographic method (monitoring shifts in blood content) can be used to identify the "normal state". In normal human subjects, it is characterized by broad band synergetic liberty (a wide spectrum of rhythmic activities between 0.01 and 5 Hz). The spectrum readily responds to changes in thermoregulatory state and/or myogenic activation by positional changes of the extremity. 3) The spectral analysis of LDA and photoplethysmographic records of the volar finger reveals predominance of active vasoconstriction during heat conserving thermoregulatory reflexes (18 degrees C ambient), predominantly passive reactions are seen at 27 degrees C. At 21-24 degrees C ("thermoregulatory indifference temperature range"), a mixed reaction pattern is seen. 4) Functional or irreversible elimination of the activity of subsystems leads to the elimination of circumscript spectral bands and/or potentiation of others. The functional differentiation of active and passive components can be utilized in the future for differential diagnosis of vascular and nervous disease state on the basis of spectral shifts and/or spectral narrowing.