The apnea-hypopnea index (AHI) is a diagnostic tool used to determine the presence and severity of obstructive sleep apnea (OSA) . It is a scale that measures the average number of apneas (complete cessation of breathing) and hypopneas (partial cessation of breathing) that occur per hour of sleep. AHI is calculated by dividing the total number of apneas and hypopneas by the number of hours of sleep. The AHI scale helps doctors calculate the severity of sleep apnea symptoms. The AHI is different from the central apnea-central hypopnea index (CAHI) used for central sleep apnea, a form of sleep apnea that develops when the brain fails to tell the respiratory muscles to breathe. The AHI is classified as follows:
- Normal sleep: AHI of fewer than five events, on average, per hour
- Mild sleep apnea: AHI of five to 14 events per hour
- Moderate sleep apnea: AHI of 15 to 29 events per hour
- Severe sleep apnea: AHI of 30 or more events per hour
The AHI provides a way to quantify breathing disruptions in people with sleep apnea, but it does have drawbacks. Although it is a key tool for doctors and sleep specialists, it must be used as part of a comprehensive evaluation.
