Measurement of oxygen tensions in cerebral tissues of rats exposed to high pressures of oxygen

Brain and cerebrospinal oxygen tensions have been measured in rats breathing air or in various high pressures of oxygen (OHP). Addition of 5% CO2 to the inspired oxygen raised cerebral oxygen tensions when rats were exposed to 2 atm abs or above. Inhibition of 75% hemoglobin saturation by para-aminopropriophenone lowered cerebral pO2 in rats breathing air, but not in rats exposed to OHP. The rate of rise of cerebral pO2 to a steady level after rapid compression was found to be faster than the rate of fall to a steady level following decompression. Addition of CO2 to the inspired gas mixture increased the rate of rise of cerebral pO2. The anesthetics urethane and pentobarbital sodium did not affect cerebral pO2 in rats breathing air or oxygen at 4 atm. The results are discussed in relation to factors contributing to oxygen poisoning at high pressures. Submitted on October 30, 1962