NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE FACILITATES RESPIRATORY MUSCLE FUNCTION DURING SLEEP IN SEVERE CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Patients with chronic respiratory insufficiency due to severe chronic obstructive pulmonary disease (COPD) and presumed respiratory muscle fatigue may benefit from therapeutic maneuvers aimed at reducing the magnitude of inspiratory muscle effort. Recent work has demonstrated that continuous positive airway pressure (CPAP) can significantly reduce inspiratory effort and work of breathing in COPD patients with acute respiratory failure. Accordingly it was reasoned that prolonged CPAP administration may similarly reduce the work of breathing in stable COPD patients with chronic respiratory insufficiency, thereby allowing recovery from respiratory muscle fatigue. The purpose of this study was to determine the feasibility of employing nasal CPAP during sleep as a means of implementing this approach to reducing inspiratory muscle effort in such patients. Standard polysomnographic parameters were recorded during nocturnal administration of nasal CPAP in eight stable patients with severe COPD (FEV1 = 26.7 +/- 3.9% of predicted). Esophageal pressure, diaphragmatic (EMGdi) and parasternal intercostal (EMGic) electromyographic activity, arterial oxyhemoglobin saturation (Sa(O2)), and transcutaneous PCO2 (Ptc(CO2)) were also measured. Breathing pattern was determined by respiratory inductive plethysmography. In each patient an optimum level of nasal CPAP could be determined that produced consistent reductions in indices of inspiratory muscle effort without changing tidal volume or breathing frequency. Highly significant reductions in the tidal excursions of esophageal pressure and the pressure-time integral for the inspiratory muscles occurred at the optimum CPAP level in all patients. EMGdi and EMGic were similarly reduced. Sa(O2) and Ptc(CO2) were unaffected by CPAP. These results indicate that nasal CPAP can effectively reduce inspiratory muscle effort during sleep in patients with severe COPD. Future work is required to determine whether long-term nasal CPAP administration can sufficiently reduce inspiratory effort to produce sustained improvement in muscle function in patients with severe COPD and presumed chronic respiratory muscle fatigue.