What is sleep apnea?Sleep-disordered breathing (SDB) is a classification of sleep abnormalities that includes Obstructive Sleep Apnea (OSA), Central Sleep Apnea (CSA) and snoring. OSA is characterized by repeated episodes, while asleep, of events including apneas (complete airway obstruction lasting at least 10 seconds), and hypopneas (partial airway obstruction lasting at least 10 seconds).
These disturbances result in recurring arousals from sleep, activation of the fight or flight response in the central nervous system, and in some cases, hypoxemia or a severe drop in blood oxygen levels. Depending upon varying definitions, the minimum significant frequency of these events may be 5-15 times per hour, and may be observed to occur up to 100 times per hour or more.
By far the most common type of SDB is OSA, where mechanical obstruction of the airway occurs due to sleep-related loss of upper airway dilator muscle tone. It is often associated with common physical characteristics such as obesity, a large overbite (retrognathia), and extra tissue crowding the back of the throat. OSA can also be influenced by physiological traits such as unstable breathing control arising within the brain. CSA, less frequently seen, is caused by these abnormalities in the control of breathing, with episodes of under-breathing leading to arousals from sleep. CSA is most common in individuals with cerebrovascular or cardiovascular disease, and in individuals treated with narcotics. Although OSA and CSA are caused by different processes, they often occur together.
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