Effect of hyperoxia, hypercapnia, and hypoxia on cerebral interstitial oxygen tension and cerebral blood flow

Abstract

The assessment of cerebral interstitial oxygen tension (piO2) can provide valuable information regarding cerebrovascular physiology and brain function. Compartment-specific cerebral piO2 was measured by 19F NMR following the infusion of an oxygen-sensitive perfluorocarbon directly into the interstitial and ventricular space of the in vivo rat brain. 19F T1 measurements were made and cerebral piO2 were obtained through in vitro calibrations. The effects of graded hyperoxia, hypercapnia, and hypoxia on piO2 and cerebral blood flow (CBF) were investigated. Under normoxia (arterial pO2 ∼ 120 mm Hg), piO2 was ∼30 mm Hg and jugular venous pO2 was ∼50 mm Hg. During hyperoxia (arterial pO2 = 90-300 mm Hg), piO2 increased linearly with the arterial pO2. Following hypercapnia (arterial pCO2 = 20-60 mm Hg), the piO2 increased sigmoidally with increasing CBF. With hypoxia (arterial pO2 = 30-40 mm Hg), CBF increased ∼56% and piO2 decreased to ∼15 mm Hg. The hypoxia-induced CBF increase was effective to some extent in compensating for the reduced piO2. This methodology may prove useful for investigating cerebral piO2 under pathologically or functionally altered conditions. © 2001 Wiley-Liss, Inc.