Intracerebral oxygen and carbon dioxide tensions in the rhesus monkey

Five rhesus monkeys (M. mulatta) were prepared by surgical placement of a stainless steel implant in the parietal area of the skull. The implant was designed to firmly hold a Teflon coated membrane of a medical mass spectrometer in an intracerebral position. Animals were consecutively exposed to varying ambient oxygen concentrations from 11% to 21%. Intracerebral PO2 and PCO2 and arterial PO2 were all stimultaneously recorded for computer analysis. Results indicate an almost linear relationship between cerebral PO2 and ambient PO2 as well as between cerebral PO2 and arterial PO2. With an ambient oxygen concentration of 21%, the cerebral Po2 and Pco2 were 13.5 +/- 3.5 mm Hg and 50.4 +/- 7.9 mm Hg, respectively. With an ambient oxygen concentration of 10.7%, these values decreased to 2.5 +/- 2.7 mm Hg and 38.0 +/- 5.6 mm Hg.