Effects of Intermittent Hypoxia on Vascular Function and Hemodynamic Control in Men

This study investigates how acute and chronic, intermittent hypoxic interventions affect vascular function and hemodynamic control in men. Ten healthy sedentary men exposed to hypoxia (i.e., 12% O 2 ) for 1 hour per day, 5 days per week for 4 to 8 weeks in a chamber of normobaric hypoxia. Stiffness of large artery and reflection of small artery, indicated by stiffness (SI) and reflection (RI) indices, respectively, were assessed by digital volume pulse measurements. Venous compliance and arterial hyperemia were measured by impedance plethysmography. The results of this study were summarized as follows: (1) immediately after hypoxic exposure for 1 hour, heart rate and venous flow resistance were increased and RI was decreased whereas blood pressure, SI, venous capacity, and hyperemic arterial flow remained unchanged; (2) intermittent hypoxia for 4 weeks attenuated the reduction of RI induced by acute hypoxic stimulus, as well as enhanced venous flow resistance and decreased venous capacity and hyperemic arterial flow; and (3) intermittent hypoxia for 8 weeks reversed the impairments of vascular function and hemodynamic control induced by 4‐week hypoxia intervention back approximately to pre‐hypoxia treatment state. We conclude that intermittent hypoxia changes regulation of arterial and venous functions and according to reactions reliant on the time course of intervention.