Impact of continuous positive airway pressure on the pulmonary changes promoted by immersion in water

OBJECTIVE: To determine whether different levels of CPAP improve the lung volumes and capacities of healthy subjects immersed in water. METHODS: This was a randomized clinical trial, conducted between April and June of 2016, involving healthy female volunteers who were using oral contraceptives. Three 20-min immersion protocols were applied: control (no CPAP); CPAP5 (CPAP at 5 cmH(2)O); and CPAP10 (CPAP at 10 cmH(2)O). We evaluated HR, SpO(2), FVC, FEV(1), the FEV(1)/FVC ratio, peak expiratory flow rate (PEFR), and FEF(25-75%)) at three time points: pre-immersion; 10 min after immersion; and 10 min after the end of each protocol. RESULTS: We evaluated 13 healthy volunteers. The CPAP10 protocol reversed the restrictive pattern of lung function induced by immersion in water, maintaining pulmonary volumes and capacities for a longer period than did the CPAP5 protocol. CONCLUSIONS: When the hemodynamic change causing a persistent lung disorder, only the application of higher positive pressures is effective in maintaining long-term improvements in the pulmonary profile.