Impact of sleep on respiratory muscle function.

Sleep has well recognised effects on respiratory muscle function, most of which are detrimental. Upper airway dilator muscle function is compromised, which predisposes to obstruction, particularly during rapid-eye-movement sleep (REM). The diaphragm and accessory muscles of respiration are differently affected by sleep. Diaphragmatic function is largely preserved, which is essential for the maintenance of adequate ventilation during sleep. However, accessory muscle function is reduced, particularly during REM sleep, which may have adverse effects on lung mechanics. These changes contribute to hypoventilation and worsening ventilation-perfusion mismatching, particularly in patients with chronic lung disease such as COPD, with resulting oxygen desaturation.