[Effects of nasal continuous positive airway pressure on lung function in patients with sleep obstructive apnea...

Sixty-one patients with obstructive sleep apnea syndrome (OSAS), 26 of whom also had chronic obstructive pulmonary disease (COPD), received treatment by nasal continuous positive airways pressure (nCPAP). To evaluate the effects of this device on daytime lung function, we analyzed pulmonary function tests before treatment with nCPAP and after a mean follow-up period of 12 months (range: 2-22 months). In patients with both OSAS and COPD, we observed a significant decrease in PaCO2 (p < 0.007), in airways resistance (p < 0.002) and in residual volume (p < 0.01); for these same patients we recorded increases in forced vital capacity (p < 0.04) and maximum inspiratory pressure (p < 0.02). We saw no change in lung function in patients with OSAS only. PaO2 increased after treatment in the 15 patients who were initially hypoxemic (p < 0.001). We conclude that after treatment with nCPAP, the greatest changes in respiratory function occur in patients with both OSAS and COPD, who also experience slight decrease in body weight. These changes may be explained by a decrease in auto-PEEP and weight loss.