How do you calculate the apnea + hypopnea index?

The apnea + hypopnea index (AHI) is calculated by taking the total number of apnea events and hypopnea events that occur during a sleep study and dividing that number by the total time spent asleep. This measure provides a standardized way to quantify the severity of sleep-disordered breathing, as it reflects the number of these events per hour of sleep rather than per hour of total time in bed.

Using total sleep time is crucial because it offers a more accurate representation of how often apneas and hypopneas occur during the time that the patient is actually experiencing sleep, rather than just the time spent in bed, which may include periods of wakefulness. This distinction can significantly impact the interpretation of a sleep study and the clinical diagnosis of conditions such as obstructive sleep apnea.

Therefore, by focusing on total sleep time, the AHI presents a clear picture of a patient's breathing interruptions, aiding in treatment decisions and management of sleep apnea.