[Microcirculatory reactivity features in almost healthy people during acute moderate hypoxia and hyperoxia modeling]

The dynamics of the microvascular circulation and tissue oxygenation in the hypoxic test and subsequent hyperoxia are considered. In 30 healthy young men indicators of microcirculation and tissue oxygenation (laser Doppler flowmetry, and the optical tissue oximetry) during the hypoxic test - HT (10 min breathing by gas mixture with 10% O2 followed by hyperoxia (30% O2) were registered. It is found that the HT does not entail changes in the relative level of tissue oxygen saturation (SO2), but leads to a relative degree of tissue oxygen extraction significant reduction (δSaO2-SO2) with a rapid recovery in the hyperoxic phase. This is accompanied by activation of neurogenic sympathetic-related vasomotor mechanisms, as well as the endothelium-dependent microvascular tone component with a reduction in blood shunting (BSh) mostly in the hyperoxic phase and not during hypoxia. The nature of the microcirculatory response to hypoxia depends on the initial individual resistance--sensitivity level to hypoxia. Among the subjects sensitive to hypoxia HT led to a significant reduction in SaO2 and δSaO2-SO2 in the absence of changes in the microcirculation regulation. Among the subjects resistant to hypoxia HT leads to the nutritive blood flow activation by increasing the initially decreased endothelium-dependent and neurogenic sympathetic components in regulation of microhaemodynamics activity, reduction of blood shunting. At the same time δSaO2-SO2 has not significantly changed, and the activation of micro blood circulation remains in the hyperoxic recovery stage. Identified functional criteria for contribution of endothelial and neurogenic vasomotor component in the regulation of microhemodynamics in HT substantiate the contribution of the microcirculatory part and confirm the important role of hyperoxic phase in the body' hypoxia-hyperoxia adaptive response.