Apnea, central sleep (CSA): Sleep apnea is a breathing disorder characterized by brief interruptions of breathing during sleep. It owes its name to a Greek word, apnea, meaning "want of breath."

There are two types of sleep apnea: central and obstructive. Central sleep apnea occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations. Obstructive sleep apnea occurs when air cannot flow into or out of the person's nose or mouth although efforts to breathe continue.

Central sleep apnea is less common than obstructive sleep apnea.