Systemic hypoxia causes cutaneous vasodilation in healthy humans.

Area of Science:

• Physiology
• Cardiovascular Science
• Thermoregulation

Background:

• Hypoxia and hypercapnia pose challenges to homeostasis by affecting sympathetic outflow and vascular smooth muscle.
• Cutaneous vasculature changes significantly impact blood pressure regulation and thermoregulation.
• Limited knowledge exists on how hypoxia and hypercapnia influence skin circulation.

Purpose of the Study:

• To investigate the effects of hypoxia and hypercapnia on cutaneous vascular conductance (CVC) in healthy subjects.
• To determine if adrenergic vasoconstriction modulates the vascular responses to hypoxia and hypercapnia in the skin.

Main Methods:

• 35 healthy subjects were studied using microdialysis fibers in the ventral forearm.
• One site was perfused with saline (control), and the other with bretylium tosylate to block sympathetic vasoconstriction.
• Skin blood flow was measured using laser-Doppler flowmetry, and CVC was calculated.

Main Results:

• Isocapnic hypoxia increased CVC in both control and bretylium-perfused sites, indicating vasodilation.
• Hyperpnea did not alter CVC.
• Hypercapnia increased CVC in the control site but not in the bretylium-perfused site, suggesting a role for adrenergic mechanisms.

Conclusions:

• Both hypoxia and hypercapnia induce modest vasodilation in nonacral skin.
• Neural adrenergic vasoconstriction does not impede hypoxic vasodilation.
• Adrenergic vasoconstriction may play a role in modulating hypercapnic vasodilation.