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.