Hyperbaric hyperoxia reduces exercising forearm blood flow in humans.

Area of Science:

• Physiology
• Exercise Physiology
• Cardiovascular Physiology

Background:

• Hypoxia during exercise increases blood flow to active muscles to maintain oxygen delivery.
• The effects of hyperoxia on skeletal muscle blood flow during exercise are not fully understood.

Purpose of the Study:

• To test the hypothesis that the hyperemic response to forearm exercise during hyperbaric hyperoxia would be blunted compared with exercise during normoxia.

Main Methods:

• Seven subjects performed forearm exercise at 20% of maximum intensity under normoxic and hyperoxic conditions within a hyperbaric chamber.
• Forearm blood flow (FBF) and forearm vascular conductance (FVC) were measured using Doppler ultrasound and calculated from FBF and blood pressure.

Main Results:

• Resting forearm blood flow and vascular conductance were lower during hyperbaric hyperoxia compared to hyperbaric normoxia.
• The increase in forearm blood flow and vascular conductance during exercise did not differ between normoxia and hyperbaric normoxia.
• However, the increase in forearm blood flow and vascular conductance during hyperbaric hyperoxia was significantly attenuated compared to normoxic conditions.

Conclusions:

• Exercise hyperemia in skeletal muscle is highly dependent on oxygen availability, particularly under hyperoxic conditions.
• The data suggest that elevated oxygen levels during hyperbaric conditions can impair the normal vasodilatory response to exercise in skeletal muscle.