Role of tobacco smoking in the determination of CO diffusion impairment in silicotic patients

: Alveolar-capillary diffusion of CO was evaluated in 48 silicotics with predominantly small irregular opacities at low profusion. The mean value of CO diffusion lay between 82 and 87% of the reference values, except for DLCOSS2 which was slightly reduced (74% of theoretical). There was no correlation between the functional data and duration of work but there was a significant reduction of the CO diffusion values according to smoking, which was greatest in those smoking more than 15 pack-years. Subjects with small irregular opacities presented lower values than those with small "p" or "q" opacities, but this difference was not apparent when only non-smokers were considered.