Impact of Self-Contained Underwater Breathing Apparatus Diving on French Military Divers’ Lung Function

<h3>Background</h3> Although acute risks concerning underwater divers are well documented, the literature regarding the long-term impacts on pulmonary function remains inconclusive. Although oxygen toxicity at high partial pressures is established for patients in intensive care, the impact of diving seems limited. <h3>Research Question</h3> What are the long-term effects of self-contained underwater breathing apparatus diving on pulmonary function in military divers? <h3>Study Design and Methods</h3> This longitudinal study used routinely collected data from Sainte-Anne Military Teaching Hospital, Toulon, France, over a 20-year follow-up period. We expressed spirometric measures as a percentage of predicted values to account for age, height, and ethnicity, and analyzed them using mixed-effects models. The impact of diving is assessed for different gas and diving apparatus. Other included variables were atopy, tobacco use, and BMI. <h3>Results</h3> A total of 331 divers were included (2,685 spirometric measurements), with an average follow-up of 23.9 years and 2,491 dives. Only male divers met inclusion criteria. Baseline FEV₁ matched predicted values (100.00%; SD, 11.98). Every 1,000 dives, FEV₁ increased by 3.21% (95% CI, 2.73-3.68; <i>P</i> < .001), regardless of gas or apparatus. FVC (3.02%; 95% CI, 2.52-3.53; <i>P</i> < .001) and forced expiratory flow when 75% of forced expiratory vital capacity has been exhaled (10.12%; 95% CI, 8.29-11.95; <i>P</i> < .001) increased, whereas FEV₁/FVC remained stable. Each BMI point increase was associated with a 0.51% rise in FVC (<i>P</i> = .010) and 0.38% rise in FEV₁ (<i>P</i> = .032), whereas each pack-year was associated with a 1.12% decline in forced expiratory flow when 75% of forced expiratory vital capacity has been exhaled (<i>P</i> = .005). <h3>Interpretation</h3> Our results show that self-contained underwater breathing apparatus diving is associated with increased pulmonary flows and volumes in this population of military divers. Prospective studies could explore the role of unmeasured confounding factors and could significantly contribute to health policies for both military and civilian divers.