What are the different types of SDB?
We start with a glossary. In apnea , breathing stops completely for ten seconds or more. A hypopnea is similar to apnea, but breathing does not stop, but only decreases. An awakening occurs when the brain notices the lack of oxygen and starts the breathing process. It is these micro-awakenings that disrupt nighttime sleep and cause the poor sleep quality that characterizes SDB. The apnea-hypopnea index (AHI) indicates the number of disturbances per hour of sleep. People with severe sleep apnea can wake up over 30 times (micro-awakenings) per hour – no wonder they feel exhausted during the day!
Obstructive sleep apnea (OSA) occurs when the muscles in the throat relax and block the upper airway during sleep. OSA is often accompanied by loud snoring or grunting, especially when awakening. Central sleep apnea (CSA) is much less common and occurs when the brain stops sending signals to the breathing muscles during sleep. The airway is not blocked, but breathing stops. In Cheyne-Stokes respiration (CSR), periods of shallow breathing are followed by deep breathing, with periodic central apneas.