Nocturnal nasal continuous positive airway pressure in patients with chronic obstructive pulmonary disease. Influence on waking respiratory muscle function.

Patients with COPD often have reduced inspiratory muscle strength and endurance as well as poor exercise tolerance. Increased inspiratory work during sleep (probably due to increased upper airway resistance) may further strain these compromised respiratory muscles in COPD patients. We hypothesized that nasal continuous positive airway pressure (CPAP) might reduce respiratory work during sleep in COPD patients and thereby improve waking inspiratory muscle function. To test this hypothesis, eight male COPD patients were treated with sustained nocturnal nasal CPAP. Inspiratory muscle strength (maximum inspiratory pressure) and endurance (sustained inspiratory pressure) as well as clinical performance (12-min walk) were assessed before and after therapy. We observed that compared with matched controls, COPD patients treated with nocturnal nasal CPAP had significant and substantial improvement in inspiratory muscle strength and endurance as well as functional ability as assessed by the 12-min walk. In addition, CPAP did not significantly alter sleep quality or oxygenation in the patients studied. We conclude that nocturnal nasal CPAP improves inspiratory muscle performance during wakefulness in COPD patients, which is very likely a product of the reduced work of breathing during sleep while these individuals received CPAP.