The apnea–hypopnea index or apnoea–hypopnoea index (AHI) is an index of sleep apnea severity that combines apneas and hypopneas. The apneas (pauses in breathing) must last for at least 10 seconds and are associated with a decrease in blood oxygenation. Combining these gives an overall sleep apnea severity score that evaluates both number sleep disruptions and degree of oxygen desaturation (low blood level).
The AHI, as with the separate apnea index and hypopnea index, is calculated by dividing the number of events by the number of hours of sleep. (AHI values are typically categorized as 5–15/hr = mild; 15–30/hr = moderate; and > 30/h = severe.)
- Ruehland WR, Rochford PD, O'Donoghue FJ, Pierce RJ, Singh P, Thornton AT (1 February 2009). "The new AASM criteria for scoring hypopneas: impact on the apnea hypopnea index". Sleep 32 (2): 150–7. PMC 2635578. PMID 19238801.
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