The Apnea–Hypopnea Index or Apnoea–Hypopnoea Index (AHI) is an index used to indicate the severity of
sleep apnea
Sleep apnea (sleep apnoea or sleep apnœa in British English) is a sleep-related breathing disorder in which repetitive Apnea, pauses in breathing, periods of shallow breathing, or collapse of the upper airway during sleep results in poor vent ...
. It is represented by the number of
apnea
Apnea (also spelled apnoea in British English) is the temporary cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the ...
and
hypopnea events per hour of sleep. Apnea is the complete absence of airflow through the nose and mouth. Hypopnea is a partial collapse of the airway, limiting breathing. Apneas (pauses in breathing) must last for at least 10 seconds and be associated with a decrease in blood oxygenation to be considered. Combining AHI and
oxygen desaturation gives an overall sleep apnea severity score that evaluates both the number of sleep breathing disruptions and the degree of oxygen desaturation (low oxygen level in the blood) during said disruptions.
The AHI is calculated by dividing the number of apnea events by the number of hours of sleep. The AHI values for adults are categorized as:
*Normal: AHI<5
*Mild sleep apnea: 5≤AHI<15
*Moderate sleep apnea: 15≤AHI<30
*Severe sleep apnea: AHI≥30
For children, because of their different physiology, an AHI in excess of 1 is considered abnormal. Underage pediatric patients presenting with AHI of 2 or greater will often be referred for treatment.
The Apnea-Hypopnea Index has been criticized for being too simplistic to accurately rate apnea and hypopnea events for their severity.
In one study, mean apnea-hypopnea duration and not AHI was found to be associated with worse hypertension.
One long apnea event is clearly worse than the same period broken up into shorter multiple events, with breathing between events, yet it would have the lower AHI.
See also
*
Obstructive sleep apnea
Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial airway obstruction, obstruction of the respiratory tract#Upper respiratory tract, upper airway lea ...
*
Oxygen saturation (medicine)
Oxygen saturation is the fraction of oxygen-saturated haemoglobin relative to total haemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal art ...
*
Respiratory disturbance index
References
Pulmonology
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