Lung function over six years among professional divers

Aims: To analyse longitudinal changes in pulmonary function in professional divers and their relation with cumulative diving exposure.

Methods: The study included 87 men at the start of their education as professional divers. At follow up one, three, and six years later, 83, 81, and 77 divers were reexamined. The median number of compressed air dives in the 77 divers over the follow up period was 196 (range 37–2000). A group of non-smoking policemen (n = 64) were subjected to follow up examinations in parallel with the divers. Assessment of lung function included dynamic lung volumes, maximal expiratory flow rates, and transfer factor for carbon monoxide (Tl_CO). The individual rates of change of the lung function variables were calculated by fitting linear regression lines to the data, expressed as percent change per year.

Results: The annual reductions in forced vital capacity (FVC) and forced expired volume in one second (FEV₁) were 0.91 (SD 1.22) and 0.84 (SD 1.28) per cent per year in divers, which were significantly higher than the reductions in the policemen of 0.24 (SD 1.04) and 0.16 (SD 1.07) per cent per year (p < 0.001). The annual reduction in the maximal expiratory flow rates at 25% and 75% of FVC expired (FEF_25% and FEF_75%) were related to the log₁₀ transformed cumulative number of dives in a multiple regression analysis (p < 0.05). The annual reductions in Tl_CO were 1.33 (SD 1.85) and 0.43 (SD 1.53) per cent per year in divers and policemen (p < 0.05).

Conclusions: FVC, FEV₁, maximal expiratory flow rates, and Tl_CO were significantly reduced in divers over the follow up period when compared with policemen. The contrasts within and between groups suggest that diving has contributed to the reduction in lung function.