Sleep apnea is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing during sleep. There are three types of sleep apnea:
Obstructive Sleep Apnea (OSA) is by far the most common type of the three accounting for more than 65% of all Sleep Apnea diagnoses. It is caused by an absence of air flow due to an occlusion (block) in the upper airway that lasts for at least 10 seconds, in spite of a continual effort to breathe. (More simply put your airway collapses and you can’t breathe).
It is characterized by repetitive pauses in breathing during sleep and is usually associated with a reduction in blood-oxygen saturation. The breathing pauses that are called "apneas" (Latin for, "without breath") typically last 20 to 40 seconds and may occur 5 to 30 or more times per hour.
Severity of the condition is measured by the number of times these pauses in breathing occur per hour of sleep (the Apnea-Hypopnea Index or AHI) and is categorized as Mild, Moderate or Severe.
OSA is also one of the causes of chronic loud snoring.
Central sleep apnea (CSA) is a disorder in which your breathing repeatedly stops and starts during sleep.
Central sleep apnea occurs because your brain doesn't send proper signals to the muscles that control your breathing. This condition is different from obstructive sleep apnea, in which you can't breathe normally because of upper airway obstruction. Central sleep apnea is less common than obstructive sleep apnea, making up less than 20% of Sleep Apnea diagnoses.
Central sleep apnea may occur as a result of other conditions, such as heart failure and stroke. Sleeping at a high altitude also may cause central sleep apnea.
Complex (or Mixed) Sleep Apnea accounts for less than 15% of sleep apnea diagnoses. Complex sleep apnea is the term used to describe a form of sleep disordered breathing in which repeated central apneas (>5/hour) persist or emerge when obstructive events are resolved (stopped) with positive airway pressure (PAP) and for which there is not a clear cause for the central apneas such as narcotics or systolic heart failure.
For those with continued central apneas on simple CPAP therapy, other treatment options include bilevel PAP, adaptive servoventilation (ASV), permissive flow limitation and/or drugs.