Inspiratory neural drive and muscle activity during sleep in moderate-to-severe COPD

The interactions between inspiratory neural drive (IND) and inspiratory muscle activity during sleep in COPD are poorly understood. We compared diaphragmatic electromyography (EMGdi) and respiratory mechanics during supine wakefulness (W) and sleep (rapid eye movement, REM; and non-REM stage 2, N2) in COPD and health. Patients with COPD (n=20; FRC 147.1±31.5%pr; post-BD FEV1 55.7±15.9%pr) and age-matched healthy controls (CTRL, n=20) completed overnight polysomnography with EMGdi(%max), tidal esophageal (Pes,%max), gastric (Pga,%max) and transdiaphragmatic pressure (Pdi,%max) measurement during stable breathing in W, N2 and REM at equivalent time-points. EMGdi, Pdi, and Pes were consistently higher in COPD vs CTRL (+167-234%; p IND and inspiratory muscle activity were elevated in COPD vs CTRL in wake and sleep. Despite this marked mechanical disadvantage in COPD, high diaphragmatic and total inspiratory effort were maintained during sleep even through IND declined sharply. This suggests additional activation of accessory muscles of inspiration during both REM and N2 sleep.