Hyperventilation and Cerebral Blood Flow

Abstract

Hypocapnic-hyperventilation has a profound, but probably temporary, effect on CBF, producing approximately a 2% decline in CBF for each 1 torr decline in Pco_co2. This effect appears to be mediated through changes in perivascular pH of the cerebral resistance vessels acting directly on the vessel wall. At low Pco_co2 the vasoconstrictor effect of short-term hypocapnic-hyperventilation is attenuated by resultant cerebral hypoxia. During prolonged hyperventilation CBF returns toward normal as the pH in the CSF is restored.