Chest
Volume 128, Issue 1, July 2005, Pages 224-228
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Clinical Investigations
Smoking
Large Lungs in Divers: Natural Selection or a Training Effect?

https://doi.org/10.1378/chest.128.1.224Get rights and content

Background

Normal spirometry is required for medical clearance of professional divers in many countries. Divers frequently have unusually large lung volumes associated with a low ratio of FEV1 to FVC (FEV1%), suggestive of obstructive airways disease. We retrospectively analyzed the records of divers in the Israeli Navy with a low FEV1% who fulfilled the criteria for large lungs, to determine whether this might be the effect of training or natural selection. We also investigated changes in pulmonary function in relation to diving experience.

Methods

A total of 171 divers with FEV1% < 80% on simple spirometry were evaluated. We conducted a retrospective analysis of lung function data for those subjects who met the criteria for large lungs.

Results

One hundred nine of 171 divers with low FEV1% met the criteria for large lungs and were included in the study. Their average age was 25 years (range, 18 to 44 years), and their mean diving experience was 7 years (range, 0 to 26 years). No difference was found in FVC values between experienced and inexperienced divers. The mean forced expiratory flow at 50% of vital capacity was significantly reduced in the most experienced group compared with the novice or less experienced divers. No difference was found in the diffusing capacity of the lung for carbon monoxide between experienced and inexperienced divers.

Conclusions

We suggest that large lungs may represent part of the natural selection for diving, rather than a training effect. Prolonged diving experience may result in the development of small airways disease.

Section snippets

Materials and Methods

One hundred seventy-one divers with FEV1% <80% on simple spirometry (ST-250; Fukuda Sangyo; Chiba, Japan) during medical evaluation were referred for further investigation. Before testing, the spirometer was calibrated according to the recommendations of the American Thoracic Society.10 FVC, FEV1, and FEV1% were measured. The best result of at least three tests was used for evaluation. All of the pulmonary function tests were conducted in a single pulmonary function laboratory by the same

Results

Of the 171 divers with low FEV1%, 109 met the criteria for both large lungs and nonsmoking and were included in the study. The remaining 62 divers were excluded for the following reasons: 6 divers had large lungs but were smokers, and the other 56 divers had pulmonary function findings, suggestive of obstructive airflow limitation of unknown etiology. Twelve of these 56 divers were smokers.

Thus, the 109 divers included in the study were healthy, nonsmoking males with no history, symptoms, or

Discussion

During diving, the respiratory system must deal with increased gas density, the effects of immersion, and the use of breathing apparatus, all of which increase respiratory mechanical load.11121314151617 Decompression stress and breathing high-oxygen concentrations can also have detrimental effects on pulmonary function.11121318 Therefore, one of the major concerns that must be addressed when assessing pulmonary fitness to dive is whether specific lung diseases might predispose the diver to

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