How is normal breathing restored after an apnea episode?

During an apneic event, increased airway resistance is sensed by the brain and triggers an arousal out of deep sleep. With each arousal, a signal is sent from the brain to the upper airway muscles to open the airway. Breathing is resumed, often with a loud snort or gasp.

Frequent arousals, although necessary for breathing to restart, prevent the patient from getting enough restorative sleep.