Transit time analysis of forced expiration in workers exposed to dust: a cross-sectional study

Maximal expiratory flow at 25% forced vital capacity (V25), V25 divided by height (V25/HT), and mean transit time (MTT) were calculated from the same forced expiratory maneuver performed in welding workers. The values were compared to determine variations between individuals and changes with age and chest X-ray findings. The results showed that MTT may be a less variable and equally sensitive measurement of the function of peripheral airways as compared with V25 and V25/HT. Its usefulness in the detection of the early changes of pneumoconiosis, however, must be further investigated in a prospective cohort study on workers exposed to various kinds of dust.