apnea

Apnea simply means a pause in breathing, a stretch of time when airflow stops. A brief pause is normal, for example between sentences or while swallowing, but a prolonged or repeated pause becomes a medical concern.

Doctors distinguish types by why airflow stops. In obstructive apnea the brain still tries to breathe but the upper airway collapses and blocks the air, as in obstructive sleep apnea. In central apnea the brainstem briefly stops sending the command to breathe, so there is no effort at all. Mixed forms combine both.

Apnea matters because each pause can lower oxygen and raise carbon dioxide until breathing resumes. Occasional short events during sleep can be normal, but frequent or long apneas disrupt sleep and strain the heart and circulation, and an apnea that does not self-correct is a medical emergency.