[Changes in the respiration of rabbits in a high pressure nitrogen-oxygen mixture]

In 14 unanesthetized rabbits, the parameters and the work of respiration, the electrical activity of respiratory muscles, the oxyhemoglobin content in the arterial blood, and the oxygen available in the cerebral cortex were studied in conditions of nitrogen-oxygen mixture (PO=0.2 kgc/cm2) under increased pressure: 6, 10, 20, 30, and 40 kgc/cm2. The 6 kgc/cm2 pressure decreased the lung ventilation, intensified the work of respiration and the electrical activity of external intercostal muscles. The 20--30 kgc/cm2 pressure entailed a gradual drop of the oxyhemoglobin content in the arterial blood and of the oxygen available in the cortex. The 40 kgc/cm2 pressure stopped the breathing in rabbits within 10--30 min. The data obtained reveal a limit of the increase in the density of inspired gas which for rabbits seems to be about 51.29 g/l.