AHI is an abbreviation commonly found in sleep apnea talk which refers to the “Apnea Hypopnea Index”.
This translates to the amount of times, per hour, your airway was either completely (apnea) or partially (hypopnea) blocked for 10 seconds or more. This is calculated by finding the total amount of times these events occur, divided by the hours of sleep you had.
You may see this figure represented by terms such as Events Per Hour or RDI (Respiratory Disturbance Index).
When looking at the AHI, it is normal to have 5 of these events or less. To have between 5-15 is considered Mild, 15-30 Moderate and 30+ of these events is considered Severe.
It is important to note that these figures are just guides. If one is diagnosed with Mild Sleep Apnea, it can still be the cause of symptoms for the patient.
Typically though, we will see patients with diagnosis of Moderate to Severe Sleep Apnea go onto treatment. So, lets say a patient is diagnosed with severe sleep apnea and they are experiencing 30 events per hour, there is a lot of room for improvement.
With modern CPAP machines, the AHI can be tracked. So, when patients go onto CPAP and they see their AHI drop below 5, it is often quite encouraging for them to see the improvements. If your AHI is not dropping as low as it should be on CPAP, there is often a perfectly fine reason for this and things that can be changed. It is a good idea to talk to your Doctor if you are concerned about your statistics.