Breath-holding pulmonary diffusing capacity was measured in four subjects at rest and during exercise in order to clarify the magnitude and the pattern of increase in diffusing capacity. Diffusing capacity increased from 29.5m//min/ Torr at rest to 45.2 m//min/Torr at the load of 130 watts in a linear fashion. Increase in diffusing capacity per unit increase in energy expenditure was almost constant among subjects whether work intensity was expressed either in mechanical units or in terms of oxygen intake. In addition, the slope of diffusing capacity on oxygen intake was found to be approximately the same among subject groups, by comparison with other reports. This equation was described by Dl (m//min/Torr) = 27.5+0.008 V02 (m//min) r==0.955 N = 40 The slope of Dl on Vc was also uniform among subjects and subject groups and the equation was as follows, Dl (m//min/Torr) = 14.2+0.272 Vc (m/) r = 0.885 N=39 This means that the unit change in Dl caused by exercise always reflects the same unit change in Vc. The data on diffusing capacity and alveolar O2 tension obtained after a 4-s and an 8-s breath-holding period implied that effects of the hypoxic breath-holding on the uniform relations of diffusing capacity on energy expenditure and on pulmonary capillary blood volume were little even at a heavy work load. Although the mechanism by which diffusing capacity increases during exercise was not made clear, it was suggested that a change in diffusing capacity reflects the distensibility of pulmonary capillaries. It was concluded that the uniform slope of diffusing capacity on energy expenditure with a relatively wide range in intensity could be a basis for evaluation of the potential increase in pulmonary capillary blood volume, instead of the traditional methods.
All Science Journal Classification (ASJC) codes
- Public Health, Environmental and Occupational Health
- Health, Toxicology and Mutagenesis