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...Institute.
Patients: Four hundred sixty-eight healthy, male, military scuba divers and 122 submariners (control subjects) were entered.
Measurements and results: Pulmonary function tests were performed in all subjects on at least three occasions with minimum interval of 1 year between first and last measurement. The decline in FE[V.sub.1] was investigated fitting a general linear model to FE[V.sub.1] across time with a factorial main-effects model for slopes and intercepts with respect to the factors group, smoking status, and baseline FE[V.sub.1]. Mean baseline age of all subjects was 32 years (SD, 9.1), and mean body mass index was 24.7 kg/[m.sup.2] (SD, 2.4). Subjects were followed up for 5 years (range, 1 to 9 years) on average. Baseline FE[V.sub.1] exceeded the predicted values in both divers and nondiving control subjects. There was no significant difference in the decline of FE[V.sub.1] between divers and control subjects. Over time, FE[V.sub.1] declined more rapidly in smokers than in nonsmokers (p = 0.0064) and declined more rapidly also in subjects with a baseline FE[V.sub.1] above average compared to subjects below average (p < 0.0001). The annual decline of FE[V.sub.1] peaked in smoking divers who had a high FE[V.sub.1] at baseline.
Conclusions: The data indicate that scuba diving is not associated with an accelerated decline in FE[V.sub.1]. Combined exposure to diving and smoking contributes to the fall of FE[V.sub.1]; therefore, smoking cessation is advised for divers.
Key words: diving; longitudinal study; long-term effects; lung function
Abbreviations: ERS = European Respiratory Society; FE[F.sub.25] = forced expiratory flow at 25% of expired FVC; FE[F.sub.50] = forced expiratory flow at 50% of expired FVC; FE[F.sub.75] = forced expiratory flow at 75% of expired FVC; RV = residual volume; TLC = total lung capacity
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Diving with scuba gear has become a popular recreational sport. In the United States, there are > 2 million adults and children [greater than or equal to] 7 years old participating in scuba diving at least once a year. (1) When diving, the lungs and airways are affected by factors related to the particular environment. Breathing cold and dry gas via the oral pathway will aggravate respiratory heat loss, and increased oxygen partial pressure at depth may elicit toxic effects on airway epithelia. (2) In addition, inert gas microemboli formed in body tissues during and after decompression will impair respiratory gas exchange when floating with the venous return to the pulmonary capillary bed. (3) Acute changes in lung function have eventually been shown after experimental deep saturation dives, (4) open-sea bounce dives, (5) and simulated hyperbaric chamber air dives. (6) The unanimous pattern of lung function changes obtained was indicative of acute obstructive airway changes.
The question whether these acute adverse effects cumulate with long-term exposure remains to be addressed. Cross-sectional studies (7-9) of lung function in divers revealed some evidence of reduced expiratory flows and volumes in divers compared with nondiving control subjects, thus supporting the assumption of the development of obstructive airways disease with cumulative diving, but there is only scarce information on longitudinal changes.
The hypothesis of the current study was that the development of chronic inflammatory airway changes from scuba diving would result in an accelerated decline in FE[V.sub.1]. Therefore, a controlled prospective investigation of lung function in a large cohort of healthy military scuba divers was carried out to follow up lung function over time.
MATERIALS AND METHODS
Study Population and Design
The cohorts were established on the individual attendance to the German Naval Medical Institute. Only healthy male subjects were included who had either been found fit to dive or fit to serve as submariners according to navy regulations. The study had been approved by an independent review board, and subjects gave informed consent. The subjects were entered only if they had at least two follow-up examinations, in order to guarantee a minimum observation period of > 1...
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