Effects of prolonged oxygen exposure at 1.5, 2.0, or 2.5 ATA on pulmonary function in men (predictive studies V).

As part of a study of human organ O2 tolerance, lung flow-volume and spirometric measurements were performed repeatedly before, during, and after continuous O2 exposures at 1.5, 2.0, and 2.5 ATA for average durations of 17.7, 9.0, and 5.7 h, respectively (effects of O2 breathing at 3.0 ATA for 3.5 h were reported previously; J. M. Clark, R. M. Jackson, C. J. Lambertsen, R. Gelfand, W. D. B. Hiller, and M. Unger. J. Appl. Physiol. 71: 878-885, 1991). Additional measurements of pulmonary mechanical function, gas exchange, and alveolar inflammatory cells were obtained before and after O2 exposure. Rates of pulmonary symptom development and lung volume reduction increased progressively with elevation of O2 pressure. Average rates of vital capacity reduction over a useful range of O2 pressures provided a valuable general description of pulmonary O2 tolerance in humans. However, the existence of multiple pulmonary effects of O2 toxicity and the complexity of their interactions require awareness that deviations from the average relationships may occur in different individuals or under varying conditions of O2 exposure and subsequent recovery. The associated pulmonary function deficits may represent responses to a composite of direct and indirect effects of O2 poisoning, along with related consequences and subsequent reactions to those effects.