[Effect of hyperoxia on oxygen tension in the blood and brain tissue]

Changes of the oxygen tension in the surface layers of cerebral cortex (PtO2) and arterial blood (PaO2) in the conditions of hyperoxia occurred in anesthetized rabbits: raising of O2 partial pressure in altitude chamber to 1.0 and 2.0 kgs/cm2 increased PaO2 from 76.5 +/- 11.4 mm Hg to 472.3 +/- 63.1 and 1138.0 +/- 79.4 mm Hg respectively. Raising of O2 partial pressure in altitude chamber from 0.2 to 6.0 kgs/cm2 increased PtO2 from 34.9 +/- 12.0 to 1087.5 +/- 149.8 mm Hg. Obvious defence reactions of the organism developed at the moment of transition from air breathing to pure oxygen breathing under the pressure of 1.0 kgs/cm2. High effectiveness of these reactions preserved with the raising of pressure to 3.0 kgs/cm2 and weakened with the further raising of pressure to 4.0-6.0 kgs/cm2. With prolongation of exposure to the 2.0-3.0 kgs/cm2 pressure the defence reactions slackened as well.