If you have shown signs or symptoms of sleep apnea, such as daytime drowsiness and morning headaches, or if a sleeping partner complains about your snoring, your next step will probably be to schedule a sleep study through a sleep clinic. This will help to confirm a sleep apnea diagnosis and inform treatment for the condition.
One of the measurements taken at the sleep clinic will be the apnea-hypopnea index (AHI). This measurement is central to determining a diagnosis of sleep apnea, and some insurers will not reimburse patients for sleep studies that don’t include this measurement.
Apnea-hypopnea quantifies the severity of the patient’s sleep apnea. The apnea component is the actual pause in breathing that occurs when the soft tissues at the rear of the throat fall backward and cover up the airway opening. This causes the patient to stop breathing repeatedly for brief periods of time during sleep. In order to qualify as an actual episode of apnea, the breathing pause must last for at least 10 seconds.
This apnea results in lower blood oxygen levels, which is what the hypopnea piece of the index measures. Technically, hypopnea can refer to any episode of shallow breathing and/or insufficient blood oxygenation, but in a sleep study, it specifically means the hypopnea resulting from apneic episodes.
Although other measurements can look at apnea and hypopnea separately, the apnea-hypopnea index combines the events and then divides them by the total number of hours of sleep. An AHI of 5-15 is considered to be mild, while 15-30 is classified as moderate. An AHI above 30 indicates a severe case of sleep apnea.
The apnea-hypopnea index is an important component of a sleep study, so when you are preparing for your study, discuss this measurement with the sleep clinic staff to ensure that it will be captured during your study. It’s the first step down the path to relief from your obstructive sleep apnea.