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

The assessment of cerebral interstitial oxygen tension (piO(2)) can provide valuable information regarding cerebrovascular physiology and brain function. Compartment-specific cerebral piO(2) was measured by (19)F NMR following the infusion of an oxygen-sensitive perfluorocarbon directly into the interstitial and ventricular space of the in vivo rat brain. (19)F T(1) measurements were made and cerebral piO(2) were obtained through in vitro calibrations. The effects of graded hyperoxia, hypercapnia, and hypoxia on piO(2) and cerebral blood flow (CBF) were investigated. Under normoxia (arterial pO(2) approximately 120 mm Hg), piO(2) was approximately 30 mm Hg and jugular venous pO(2) was approximately 50 mm Hg. During hyperoxia (arterial pO(2) = 90-300 mm Hg), piO(2) increased linearly with the arterial pO(2). Following hypercapnia (arterial pCO(2) = 20-60 mm Hg), the piO(2) increased sigmoidally with increasing CBF. With hypoxia (arterial pO(2) = 30-40 mm Hg), CBF increased approximately 56% and piO(2) decreased to approximately 15 mm Hg. The hypoxia-induced CBF increase was effective to some extent in compensating for the reduced piO(2). This methodology may prove useful for investigating cerebral piO(2) under pathologically or functionally altered conditions. Magn Reson Med 45:61-70, 2001.