THE EFFECT OF POSITIVE PRESSURE BREATHING ON ARTERIAL OXYGEN SATURATION AND PULMONARY VENTILATION IN SUBJECTS EXPOSED TO HIGH TRANSVERSE ACCELERATION

Twenty-two centrifuge runs were performed on eight subjects in whom arterial oxygen saturation was continually monitored, while the subjects were exposed to various transverse accelerations +Gx at a seat angle of 6 degrees head up. These runs were made during conditions of breathing: air, air positive pressure, pure oxygen, and pure oxygen positive pressure. The positive pressure was metered automatically to provide 3 mm Hg per G above ambient pressure. The results of this experiment show that the slope of the curve of oxygen saturation plotted against time for air and air positive pressure decreased approximately 3 percent every 10 seconds, beginning 10 to 20 seconds after the onset of the acceleration. During the oxygen breathing studies, a lowering in arterial oxygen saturation was observed approximately 100 seconds after the onset of acceleration. A method is suggested for estimating physiological limits for theoretical profiles of acceleration G plotted against time. (Author)