The apnea-hypopnea index
(AHI) is an index of severity that combines apneas
. Combining them both gives an overall severity of sleep apnea
including sleep disruptions and desaturations (a low level of oxygen in the blood). The apnea-hypopnea index, like the apnea index and hypopnea index, is calculated by dividing the number of apneas and hypopneas by the number of hours of sleep.