Definition and types of sleep apnea

Sleep apnea

• Sleep apnea syndromes are a group of serious sleep disorders in which breathing repeatedly stops long enough during sleep to decrease the amount of oxygen and increase the amount of carbon dioxide in the blood and brain.

• Occurs when breathing is temporily interrupted during sleep and there are 3 types.

Obstructive sleep apnea

• This disorder is characterized by intermittent closure/collapse of the pharyngeal airway which causes apnoeic episodes during sleep.

• These are terminated by partial arousal.

• The most common type, caused by a blockage in the throat or upper airway.

Central sleep apnea

• A much rarer type

• Caused by dysfunctioning in part of the brain that controls breathing.

• Normally, the brain stem is very sensitive to changes in blood level of carbon dioxide. When the level is high the brain stem signals the respiratory muscles to breathe harder and faster to remove carbon dioxide through expiration and vice versa.

• In central sleep apnea, the brain stem is less sensitive to changes in carbon dioxide level.

• Because the brain stem responds slowly to the build up of carbon dioxide in blood, the body’s respond will be exaggerated, resulting in prolonged hyperventilation.

• Similarly, because the brain stem response slowly to the removal of carbon dioxide in blood, the body’s response – a pause in breathing – is prolonged.

• Brain stem dysfunction that leads to central sleep apnea may be due to brain tumours, stroke.

• People who have heart failure may have central sleep apnea.

• Central sleep apnea is not associated with obesity.

Mixed sleep apnea

• A combination of obstructive sleep apnea and central sleep apnea.

• For example, obstructive sleep apnea sometimes causes central sleep apnea – by decreasing the oxygen levels and increasing carbon dioxide levels in the blood long enough to cause the brain stem to malfunction

• It is rare