Apnea Hypopnea Index

AHI (Apnea Hypopnea Index) is the number of apneas and hypopneas per hour. Or an index for sleep apnea. 5-20 mild, 21-50 moderate, above 50 severe.

Less than 5 events (apnea or hypopnea) per hour is considered normal. 5 or more events per hour is considered Mild sleep apnea 15+ considered Moderate 30+ considered Severe (from T. S. Johnson MD, Sleep Apnea - The Phantom of the Night, page 211)

Flow limitation or Upper Airway Resistance Syndrome (UARS) is another important, subtle form of SBD. The airflow meets resistance in the nose or mouth, causing the brain to waken the sleeper. The American Academy of Sleep Medicine advocates counting apneas, hypopneas, and flow limitations/UARS for the Respiratory Disturbance Index, RDI, which is more comprehensive than the Apnea-Hypopnea Index.

To determine AHI add the total number of Apnea events, plus Hypopnea events and divide by the total number of minutes of actual sleep time, then multiplied by 60.

Example

Apnea + Hypopnea divided by actual sleep time, then multiply by 60

200 Apnea 200 Hypopnea

400 Total Events

420 Actual Sleep time (7 hours)

Divide 400 by 420 =.95 x 60 = 57 AHI (Severe OSA)

Two measurements of Sleep Disordered Breathing Apnea(SDB)

The Greek word “apnea” means “without breath.” You stop breathing during sleep for ten seconds or longer. Hypopnea. There is airflow through your throat but at a much reduced level, which leads to not getting enough oxygen. It’s abnormally shallow breathing lasting at least ten seconds.