Apnea/Hypopnea Index (AHI)
Your AHI is the most important number on your sleep study results. It’ll tell you the severity of your sleep apnea.
< 5 = normal AHI score in an adult. If you have an AHI score of 4 or lower, you don’t have sleep apnea.
5-15 = mild sleep apnea.
15-30 = moderate sleep apnea.
> 30 = severe sleep apnea.
Let’s dive a little deeper into the AHI and how a sleep study will determine your score.
The “A” in AHI stands for apnea. An apnea episode is when you stop breathing for at least 10 seconds while you are asleep.
The “H” in AHI stands for hypopnea. A hypopnea episode is when you experience 50% less ventilation which results in a 4% or more reduction of oxygen in your arteries. Basically, you have a partial obstruction in your airway, which doesn’t allow you to get all the oxygen you need, but it’s not a full obstruction that causes a true apnea episode. Your sleeping partner probably hears this partial obstruction—snoring!
So your AHI score is a combination of how many apneas and hypopneas you experienced during the night divided by the number of hours you slept. So let’s say that you stopped breathing 20 times during the night, had a partial obstruction 40 times, and slept for eight hours. Your AHI score would equal (20+40)/8, which is 7.5, putting your AHI in the mild sleep apnea category.
How does the sleep study determine my breathing and blood oxygen level?
Your home sleep study is equipped with many sensors that collect and store data in the ApneaLink Air device. Home sleep studies from SleepTest.com have a nasal cannula—a tube that fits just into the beginning of your nostrils. When you breathe, the tube carries your breath to the ApneaLink Air device, which records your data.
Your sleep test also has an effort sensor and chest belt that help to collect data on how hard it is for you to breathe (was there an obstruction causing hypopnea?)
To determine your blood oxygen level, your sleep test has an oximeter tubing and an oximeter sensor.
These sensors collect data on your breathing and oxygen to determine if you had any apneas or hypopneas.