Measurement of Sleep Apnea

The most common measurement of Sleep Apnea is the AHI (Apnea Hypopnea Index). This is the average number of apneas and hypopneas per hour. Apneas being the number of times breathing has stopped for 10 seconds or more, and hypopneas being the number of times the airflow has been reduced by 50% or more for 10 seconds or more.

Often apneas will be indexed separately from the hypopneas. AI would be the Apnea Index (number of apneas per hour). The HI would be Hypopnea Index (number of hypopneas per hour). AHI = AI + HI.

An AHI of under 5 is generally considered normal. This would seem to indicate that an AHI of 5 or more could be treated. But, insurance companies have various policies on how high it needs to be before they will pay for treatment. With some companies, AHI values between 5 & 15 are only treated if accompanied by other defined symptoms.

In a sleep lab, they can tell if an apnea is an obstructive apnea or central apnea. The sleep lab uses a large number of sensors in addition to just air sensors over your nose and mouth. They measure your blood oxygen saturation (oximeter), they chart your heartbeats (EKG), they chart your brainwaves (EEG), chest expansion, they even have sensors on your legs to measure how many times you kick during the night.

The most important measurements used for Sleep Apnea are the AHI, and the blood oxygen saturation.