[abstract] NARROWING OF SMALL LUNG AIRWAYS IN COMMERCIAL DIVERS.

Abstract

An association between diving and narrowing of small lung airways was suggested by Davey et al. (1984) who observed that maximal expiratory flow at small lung volumes (MEF25% VC) was significantly reduced in commercial divers compared with fire brigadesmen of similar age, stature, and vital capacity despite the fire brigadesmen being exposed to fumes from fires and including a somewhat larger proportion of smokers. The association has now been reinvestigated using as subjects 115 commercial divers attending for their annual medical examination. The men had been diving for longer than those studied previously (on average 9.8 years compared to 6.5 years). Spirometry was performed at atmospheric pressure (1 ATA) using a bellows spirometer (McDermott): this was calibrated before each measurement session. Stature was measured using a stadiometer (Harpenden). The analysis was cross-sectional. After allowing for age, stature and smoking (yes/no), forced expiratory volume (FEV) was correlated with maximum depth but forced vital capacity was1independent of diving exposure. Maximal flow rate at small lung volumes was negatively correlated with years diving such that: MEF25% VC = 2.39 -0.032 (years diving) -0.28 (if smoker) r2=0.142 There was no association between smoking history and diving exposure. This result provides independent confirmation for the hypothesis that diving causes persistent narrowing of small airways. Loss of lung elasticity cannot be excluded as a possible mechanism. Davey I.et al. (1984) J. Appl. Physiol. 56:1655-1658.