Apnea-Hypopnea Index

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In sleep medicine, the apnea-hypopnea index (AHI) describes the average number of apnea ( listen ? / I ) and hypopnea episodes per hour of sleep. It is an indication of the severity of a "sleep-related breathing disorder" and is also used to monitor the success of therapy. Audio file / audio sample

Calculation of the AHI

To determine the AHI, the sum of the number of apneas and hypopneas is formed and divided by the total sleep time ("Total sleep time", an indication in hours). The number of respiratory events apnea (breathing pauses) and hypopnea (times with reduced respiratory flow) are determined in the sleep laboratory during an examination using polysomnography .

Due to differences in the evaluation of the hypopneas according to older rules and the two now valid, alternatively applicable rules, there are considerable differences in the determination of the AHI with effects on the comparability of study results.

Using the AHI

For the diagnosis of certain "sleep-related breathing disorders" such as obstructive sleep apnea syndrome (OSAS), certain values ​​are set for the AHI in addition to other characteristics.

The control of therapy determines whether the treatment reduces the number of respiratory events in question accordingly.

Severity according to AHI

There is no uniform classification of severity using the AHI. The American Society for Sleep Medicine (AASM), which has published detailed specifications for determining the AHI, indicates the severity of an OSAS as a grading:

  • "Mild": AHI 5-15,
  • "Moderate": AHI 15-30,
  • "Severe": AHI greater than 30

and combines the statement with references to the tendency to fall asleep during the day in certain situations; (often using the Epworth Sleepiness Scale ).

According to the medical guideline "Non-restful sleep - sleep disorders", OSAS "from an AHI> 15 and <30" is classified as moderate, and "from an AHI> 30 as severe".

Other authors use terms such as easy, moderate and difficult and draw boundaries with an AHI of 20 or 40 or use mathematically and technically more precise boundaries with formulations such as “less than or equal” without overlapping the areas. In view of the fact that therapy recommendations do not only depend on the degree of severity and that the measurement results are subject to fluctuations from night to night anyway, this is not significant.

Individual evidence

  1. ↑ Conrad Iber, Sonia Ancoli-Israel, Andrew L. Chesson, Stuart F. Quan: The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology, and Technical Specifications . Ed .: American Academy of Sleep Medicine. AASM, Westchester, Ill. 2007.
  2. ↑ Warren R. Rühland, Peter D. Rochford, Fergal J. O'Donoghue, Robert J. Pierce, Parmjit Singh, Andrew T. Thornton: The New AASM Criteria for scoring hypopneas: Impact on the apnea hypopnea index . In: Sleep . Vol. 32, No. 2 , 2009, p. 150–157 , PMC 2635578 (free full text) - (English).
  3. ↑ Boris A. Stuck, Joachim T. Maurer, Michael Schredl , Hans-Günter Weeß: Practice of sleep medicine: sleep disorders in adults and children . Springer, Heidelberg 2009, ISBN 978-3-540-88699-0 , pp. 125 .
  4. ↑ S3 guideline for non-restful sleep / sleep disorders of the German Society for Sleep Research and Sleep Medicine (DGSM). In: AWMF online (as of 2009).