Ahi

AHI is the acronym for "Apnea Hypopnea Index". The AHI indicates the average number of apnea and hypopnea events per hour of sleep time and is determined in the sleep laboratory using polysomnography. Here, apneas refer to breathing pauses of ≥10 seconds. Hypopneas are characterized by a reduction of the respiratory flow by ≥50% for ≥10 seconds, accompanied by a drop in oxygen saturation of ≥3% or arousal (wake-up reaction in EEG).

AHI <5: normal

AHI 5-14/h: mild sleep apnea syndrome

AHI 15-29/h: moderate sleep apnea syndrome

AHI >30/h: severe sleep apnea syndrome

In sleep medicine, the AHI is used as a parameter to assess the severity of sleep-related respiratory disorders (G47.39) (see also OSAS). It is available for diagnostics as well as therapy control.

Calculation:

Apnea-Hypopnea-Index (AHI): (hypopnea + apnea)/hour sleep time

Meaning:

Obstructive sleep apnoea syndrome (OSAS) in AHI >15/hour sleep time or >5/hour sleep time + with typical clinical symptoms

Important: An apnea-hypopnea index (AHI) does not always have to be accompanied by clinical symptoms. There are also patients who, despite high AHIs, show no or only minor clinical symptoms.

Supplement:

The ODI is measured correlatively by means of a pulse oximeter. ODI means O2 desaturation index/ O2 desaturation index, which depicts the oxygen decrease of >3% during apneas and hypopneas and correlates with the AHI.

See article OSAS (obstructive sleep apnoea syndrome) - Therapy of OSAS

1. Herold G et al (2018) Internal Medicine Herold Verlag SS. 342, 343
2. https://www.awmf.org/uploads/tx_szleitlinien/063-001l_S3_SBAS_2017-08_2.pdf
3. www.dgsm.de