THE EFFECT OF THE INHALATION OF HIGH AND LOW OXYGEN CONCENTRATIONS ON RESPIRATION, PULSE RATE, BALLISTOCARDIOGRAM AND ARTERIAL OXYGEN SATURATION (OXIMETER) OF NORMAL INDIVIDUALS

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Abstract
The respiratory and circulatory responses of 81 normal individuals to the inhalation of 100% O2 and 18, 16, 14.5, 12, 10 or 8% O2 in N were studied. An immediate decrease in pulse rate or respiratory min. vol. occurred in 28 of 33 subjects when inhalation of 100% O2 followed room air. This suggests that some chemoreceptors of the carotid and aortic bodies were tonically active at the O2 tension present in the arterial blood of many normal men breathing room air at sea level. An increased min. vol. of respiration was noted in only a few individuals breathing 18% O2, the majority showing no significant change until 16% O2 was inhaled. The respiratory response to anoxia was characterized by extreme individual variability and by the fact that only slight stimulation was noted until 10 or 8% O2 was inhaled. The response of the circulatory system to anoxia differed markedly from the respiratory response. Significant increase in pulse rate occurred when the conc. of O in the inspired air was reduced from 20.9 to 18%. Progressive increases in pulse rate accompanied further reduction in inspired O2 conc. Additional evidence of the respiratory stimulant action of 100% O2 was obtained. Brady-cardia and a reduction of cardiac output/min. were noted simultaneously under these conditions. The wide range in arterial O2 saturation described by others for individuals breathing the same low O2 mixture was confirmed.