Effects of continuous positive airway pressure on lung function in patients with chronic obstructive pulmonary disease and sleep disordered breathing.

OBJECTIVE

Sleep disordered breathing (SDB), namely hypoventilation and obstructive sleep apnoea, occur in about 50% of patients with severe chronic obstructive pulmonary disease (COPD). Previous studies that have investigated the reversal of SDB in such patients with nasally applied intermittent positive airway pressure have reported a fall in PaCO2 but little change in airflow obstruction. We reasoned that the lack of improvement in airflow obstruction may be due to insufficient expiratory pressure. Accordingly, we sought to determine the effects of chronic nasal continuous positive airway pressure (CPAP), at highest tolerable levels, upon blood gases and airflow obstruction in patients with severe COPD and SDB.

METHODOLOGY: Fourteen patients were studied, ten of whom were able to tolerate CPAP (10.2 +/- 0.9 cmH2O) for at least 3 months.

RESULTS

Within the CPAP compliant group, there was a fall in PaCO2 (58.0 +/- 3.5 to 48.0 +/- 0.9 mmHg, P = 0.015) associated with a rise in PaO2 (54.8 +/- 3.8 to 63.2 +/- 1.8 mmHg, P = 0.015) and forced expiratory volume in 1 s (0.95 +/- 0.13 to 1.10 +/- 0.13 L, P < 0.005). Concurrent with these improvements was a substantial fall in hospitalization rates (from 3.85 to 0.73 admissions per annum).

CONCLUSION

Improvements in gas exchange, airflow obstruction and hospitalization rates were observed in patients with COPD and SDB treated with nasal CPAP during sleep.