Dynamic oscillatory circuit of regulation of capillary hemodynamics

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We used laser Doppler flowmetry with wavelet analysis of blood flow oscillations, computer capillaroscopy, and thermometry of the nail bed in 30 subjects to show an important role of the oscillatory circuit in the regulation of capillary hemodynamics, number of functioning capillaries, and linear and volumetric velocity of blood flow. The number of functioning capillaries is regulated by oscillations of myogenic and sensory peptidergic origin. The appearance of sensory oscillations, especially high-amplitude oscillations, is an adaptive neurotrophic mechanism that significantly increases the number of functioning capillaries and intensity of blood flow from arterioles to capillaries. The linear velocity of blood flow depends on both the tone of microvessels and changes in the dynamic component of blood pressure. Under conditions of skin hypoperfusion, the mean linear velocity of capillary blood flow may be inversely related to the extracapillary perfusion, including the amplitude of heart rate (Ah) and oscillations of the tone of precapillary sphincters, whereas under conditions of vasodilation and increased skin perfusion, it may be inversely related to the amplitude of arteriolar oscillations of endothelial or neurogenic sympathetic origin (Amaxe + n) and the shunting index. The Ah affects the linear velocity of blood flow in the arterial part of capillaries, whereas the Amaxe + n influences the same factor in the venous part. The contribution of oscillations to the regulation of the linear velocity varies depending on the perfusion and skin temperature. The resultant tone of distributing microvessels is determined by the competition between the stationary and oscillatory components. In addition to changes in the amplitude, the frequency of vasomotions may also be important. The regulatory importance of the oscillatory circuit is increased with a decrease in the skin blood flow.

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