Respiratory Sleep Physiology

Regulation of respiration differs significantly between wakefulness and sleep. Respiration during wakefulness is influenced by not only automatic control but also voluntary and behavioral control. Sleep is associated with definite changes in respiratory function. With the onset of sleep, voluntary control of ventilation that overrides automatic control during wakefulness becomes terminated. Also ventilatory response to various stimuli including hypoxemia and hypercapnia is decreased. With these reasons respiration during sleep becomes fragile and unstable so that marked hypoxemia can be happened in patients with lung disease especially during REM sleep. Obstructive sleep apnea may also be developed if upper airway resistance is increased in addition to these blunted ventilatory responses.