Apnea

Apnea, cessation of breathing. Periods of apnea in which breathing ceases for a few seconds before resuming may occur during sleep. When apnea alternates with periods of rapid, heavy breathing (hyperapnea), such cycles are called Cheyne-Stokes respiration; they may be due to lack of oxygen in the brain, accumulation of acid in the blood, increased pressure on the brain stem, or heart failure. Apnea may be associated with such harmful conditions as irregularities in heartbeat, high blood pressure, and decreased contractile force of the heart muscle. It has also been linked to some cases of sudden infant death syndrome (SIDS).

Sleep apnea may be due to obstruction of the airway (obstructive sleep apnea), to some abnormality in the part of the brain that controls respiration (central sleep apnea), or to both (mixed sleep apnea). Obesity may be a contributing factor; people who suffer from sleep apnea are often advised to reduce, and also to avoid sedative or hypnotic drugs. Researchers can sometimes trace the cause to damage in areas of the brain involved with respiratory control.