Apnea–hypopnea index

Apnea–hypopnea index (AHI) is a medical term used to describe the severity of sleep apnea. It is represented by the number of apnea and hypopnea events per hour of sleep. The etymology of the term comes from the Greek words "apnoia", which means "want of breath" and "hypopnoia", which means "underbreathing".

Definition

The Apnea–hypopnea index (AHI) is an index used to indicate the severity of sleep apnea. It is calculated by dividing the number of apnea events (pauses in breathing) and hypopnea events (periods of shallow breathing) by the number of hours of sleep.

Classification

The AHI is used to classify the severity of sleep apnea:

• Normal: AHI < 5
• Mild sleep apnea: AHI ≥ 5, but < 15
• Moderate sleep apnea: AHI ≥ 15, but < 30
• Severe sleep apnea: AHI ≥ 30

Measurement

The AHI is typically measured as part of a polysomnography (sleep study). During the study, various physiological parameters are monitored, including airflow, respiratory effort, and blood oxygen levels. The number of apnea and hypopnea events are then counted and divided by the number of hours of sleep to calculate the AHI.

Related Terms

• Apnea: A pause in breathing that lasts for at least 10 seconds.
• Hypopnea: A decrease in breathing that lasts for at least 10 seconds.
• Polysomnography: A type of sleep study used to diagnose sleep disorders.
• Sleep apnea: A sleep disorder characterized by pauses in breathing or periods of shallow breathing during sleep.

See Also

• Sleep disorder
• Obstructive sleep apnea
• Central sleep apnea

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