Obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common sleep apnea caused by obstruction of the airway. It is characterized by pauses in breathing during sleep. These episodes, called apneas (literally, "without breath"), each last long enough that one or more breaths are missed, and occur repeatedly throughout sleep. In obstructive sleep apnea, breathing is interrupted by a physical block to airflow, despite the effort to breathe.

The individual with sleep apnea is rarely aware of having difficulty breathing, even upon awakening. Sleep apnea is recognized as a problem by others witnessing the individual during episodes or is suspected because of its effects on the body (sequelae). Symptoms may be present for years, even decades without identification, during which time the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance.

Since the muscle tone of the body ordinarily relaxes during sleep, and since, at the level of the throat, the human airway is composed of walls of soft tissue, which can collapse, it is easy to understand how breathing can be obstructed during sleep. Although a very low level of obstructive sleep apnea is considered to be within the bounds of normal sleep, and many individuals experience episodes of obstructive sleep apnea at some point in life, a much smaller percentage of people are afflicted with chronic, severe obstructive sleep apnea.