Pulmonary Function in Man under Prolonged Acceleration II. Correlation of Arterial Blood Oxygen Saturation with Ventilation and Gas Being Breathed

摘要

Arterial blood oxygen saturation was studied by ear oximetry in 8 subjects undergoing prolonged forward (+Gx) acceleration. The effects on saturation of voluntary breathing patterns and the composition of the inspired gas were noted. Under +4Gx saturation levels were stable after two minutes. The degree of unsaturation could be modified to a small extent by voluntary breathing efforts. The level of saturation reached correlated significantly with the minute volume breathed. In contrast, under +8Gx saturation levels were significantly lower and were still falling after two minutes. Saturation levels were not significantly changed by voluntary breathing efforts and there was no significant correlation between level of saturation reached and minute volume breathed. Breathing of oxygen delayed the onset of arterial blood oxygen unsaturation. After two minutes under +8Gx, levels were 20% higher when the subjects breathed oxygen than when they breathed air. When subjects changed from air to oxygen or from oxygen to air on attaining peak acceleration, the effects of the 'prebreathed' gas were apparent for as long as two minutes, suggesting that the prebreathed gas was effectively trapped in some parts of the lung. (Author)