Controlled, dosed, uninterrupted and continuous oxygen treatment was applied in 63 patients with global respiratory insufficiency, through a nasopharyngeal catheter in concentrations to 30 per cent. PaO2, is elevated with and average of 12 mm mercury column after 30 minutes 25% oxygen breathing and PaCO2--at an average of 8 mm mercury column. PaO2 level was kept after 24 hours whereas PaCO2 decreased at an average of 4 mm mercury column. Besides, respiration and pulse rate are decelerated, secondary polyglobulia decreases, cardiac and renal function is improved. Those changes are interpreted as patients' adaptation to oxygen breathing. The adaptation to oxygen breathing decreases the danger of critical intensification of the respiratory depression in the course of the treatment and conditions for a successful application of O2 treatment at home are created.