Pulmonary diffusing capacity for carbon monoxide in simple coal workers' pneumoconiosis.

The lung diffusing capacity for carbon monoxide (DLCO single-breath) and its two components, the capillary blood volume (Vc) and the diffusing capacity of the membrane (DMCO) were measured at rest in 43 miners and 141 control subjects, the values in whom enabled reference formulae to be established; in 30 control subjects and in the majority of the miners these indices were measured during exercise. The main results are as follows: the diffusion indices are on average slightly decreased in simple coal workers' pneumoconiosis; both DMCO and Vc contribute to the lowering of DLCO, at rest and during exercise; individually Vc is more often significantly altered than DMCO; on effort the percentage increase of DLCO is normal in coal miners; the data during exercise suggest that smoking habit contributes more to lowering DLCO than does pneumoconiosis itself; lastly the diffusion indices are lower in miners with "pin-head" than those with micronodular opacities: this tendency is more pronounced during exercise. These findings are discussed.