Sleep apnea is generally established by pauses in breathing during sleep. Sleep apnea occurs when the tissue in the back of the throat collapses and blocks the airway. The breathing pause lasts at least 10 seconds and can occur 10 or more times an hour. Apnea lowers the oxygen level in the blood leaving the patient vulnerable to hypertension, stroke and other cardiovascular problems. The most common signs of sleep apnea are loud snoring, choking or gasping during sleep, and fighting sleepiness during the day. In addition to continuous positive airway pressure, treatment includes losing weight, sleeping on your side instead of your back, avoiding alcohol and tobacco.
The standard definition of any apneic event includes a minimum 10 second interval between breaths, with either a neurological arousal (3-second or greater shift in EEG frequency, measured at C3, C4, O1, or O2), or a blood oxygen desaturation of 3-4 percent or greater, or both arousal and desaturation.
There are three distinct forms of sleep apnea: Central, Obstructive, and Complex (complex is a combination of central and obstructive) with 0.4%, 84% and 15% making up their respective percentages of cases.
Breathing is interrupted by the lack of effort in central sleep apnea; in obstructive sleep apnea, breathing is interrupted by a physical block to airflow despite effort. In mixed sleep apnea, there is a transition from central to obstructive features during the events themselves. Regardless of type, 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.