What is the role of the apnea hypopnea index (API) in the workup of childhood obstructive sleep apnea (OSA)?

Updated: Feb 13, 2019
  • Author: Mary E Cataletto, MD; Chief Editor: Denise Serebrisky, MD  more...
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Individuals with obstructive sleep apnea syndrome have pathologic degrees of obstructive apnea, obstructive hypopnea, or both. Severity is quantified using a polysomnographic-derived index known as the apnea hypopnea index (AHI). The AHI is the total number of apneas and hypopneas that occur divided by the total duration of sleep in hours. An AHI of 1 or less is considered to be normal by pediatric standards. An AHI of 1-5 is very mildly increased, 5-10 is mildly increased, 10-20 is moderately increased, and greater than 20 is severely abnormal.

Obstructive hypopnea (OH) in children is a sleep-related breathing disorder that is considered a variation of obstructive sleep apnea. Children with OH may have an AHI in the normal range, but they have episodic periods of hypercapnia, as identified on the basis of end-tidal (ET) CO2 monitors. Peak ET CO2 measurements of greater than 53 mm Hg are considered abnormal. The percentage of sleep time spent with ET CO2 measurements greater than 50 mm Hg should not be more than 9%.

Most physicians who treat children with sleep apnea generally recommend specific interventions when the AHI is greater than 5 or respiratory events are associated with oxygen desaturations of less than 85%. When the AHI falls to between 1 and 5, other clinical factors must be taken into account to determine whether to pursue adenotonsillectomy or other therapy.

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