Post-exercise reduction in diffusing capacity of the lung after moderate intensity running and swimming

A reduction in transfer factor of the lung for carbon monoxide (Tl(co)) is a consistent finding after saturation dives and is reported after some open sea air dives. Several diving associated factors may contribute to this reduction in Tl(co) including hyperoxia, venous gas microembolism, increased breathing resistance and immersion. Exercise, which inevitably is associated with open sea diving, may itself cause a reduction in Tl(co) up to at least 12 hours post-exercise. Six trained swimmers and six trained runners who had never dived performed 30 min moderate intensity swimming and running on different days and in random order at approximately 75% of their maximal heart rate. Lung function including a flow-volume loop and Tl(co) was measured 30 min before and 60-90 min after exercise. There were no significant changes in dynamic lung volumes or maximal expiratory flow rates, but there was a reduction in Tl(co) of 4.5 (SD = 4.8) and 4.7 (SD = 4.6) % after swimming and running respectively (p < 0.01). There was no difference in this response between runners and swimmers, and the response was not associated with lung size. Even moderate exercise preceding measurements of Tl(co) should generally be accounted for, and this effect may contribute significantly to lung function changes immediately after open sea dives.