Hyperventilation and human calf blood flow.

COFFMAN, JAY D., AND PETER ALLY. Hyperventilation and human calf blood $0~. Am. J. Physiol. 21 I (5): 1255-1260. rg66.-Calf blood flow was measured in normal subjects by venous occlusion plethysmography, and capillary blood flow by the disappearance rate of an intramuscular injection of NaI131 before and during hyperventilation at 30 breaths/min for 3 min. Hyperventilation with room air produced a significant increase in plethysmographic calf blood flow, a decrease in vascular resistance, and an increase in the disappearance rate of NaI i31. Hyperventilation with 5 YO carbon dioxide in oxygen produced no significant change in calf blood flow, vascular resistance, or NaI 131 disappearance rate. After IO mg propranolol was injected intravenously, a significant decrease occurred in calf blood flow but not in vascular resistance; the vasodilatation previously induced by intravenous epinephsine was replaced by vasoconstriction. Propranolol failed to completely block the increase in calf blood flow and decrease in vascular resistance during hyperventilation, although a significant but small attenuation did occur. It is concluded that hyperventilation produces an increase in muscle capillary blood flow which is partially but not entirely mediated by stimulation of beta receptors.