Effects of ambient cold and depth on lung function in humans after a single scuba dive

This study evaluated the subacute respiratory effects of diving, to try to separate the effects of ambient temperature from those of depth. In the fir st experiment 10 healthy men made a compressed-air dive to 50 m that expose d them to cold. They were compared with 10 matched control subjects who und erwent the same dive profile but were exposed to a comfortable temperature. In the second experiment 16 healthy subjects made randomized cold dives to both 50 in and 10 in. Pulmonary function tests were made before, after 1 h , and 24 h after the dives. In the first experiment there was an increase i n residual volume (P < 0.05) and a decrease in forced expiratory volume at 1 s (FEV1), in forced vital capacity (FVC) and in mid-expiratory flow at 75 % of FVC (MEF75) 1 h after the cold dives (P < 0.05). In the second experim ent significant increases in specific air-ways resistance (sR(AW)) (P < 0.0 5) and decreases in FEV I (P < 0.01), in MEF75 (P < 0.05), and in mid-expir atory flow at 25% of FVC (P < 0.05), were obtained after the 50 m-dives, wh ereas sR(AW) increased after the 10 m-dives (P < 0.05). The respiratory pat tern observed 1 h after cold dives to 50 m indicated airway narrowing. The changes after cold dives to 10 in, however, were of minor magnitude. Both c old and depth seemed to contribute to the adverse effects of a single compr essed-air dive on pulmonary function.