Study of the changes in respiratory function in self-contained underwater breathing apparatus divers

Background: The objective was to investigate the respiratory function of professional divers by conducting spirometry and to compare the data obtained with those of non-divers. Materials and methods: This study involved 52 military divers who carried out dives at small and medium depths using a self-contained underwater breathing apparatus (SCUBA) with open-circuit regulators attached to a mouthpiece. The control group consisted of 48 persons from deck commands with similar physiological characteristics and lifestyle that were not divers and had never been under increased pressure. Results: It was found that, compared with non-divers, the spirometry parameters of the divers are charac- terised by higher values of forced vital capacity (FVC) of the lungs (p = 0.02), but significantly lower values of the mid-expiratory flow (MEF) parameters: MEF25 (p = 0.06), MEF50 (p = 0.04), and MEF75 (p = 0.01), as well as for the ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FEV1/FVC; p = 0.001) and MEF25–75/FVC ratio (p < 0.001). Conclusions: Hyperoxia, gas decompression bubbles, hypothermia, mouth-breathing dry, cold, compressed air, and other factors accompanying the diving activity are capable of initiating damage to the airways, which is reflected in characteristic changes in spirometry. The pattern of these changes is consistent with small airway obstruction and they could be related mostly to diving activities.