What is the pathophysiology of apneas and hypopneas in childhood obstructive sleep apnea (OSA)?

Updated: Feb 13, 2019
  • Author: Mary E Cataletto, MD; Chief Editor: Denise Serebrisky, MD  more...
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Answer

Physiologic recording methods can differentiate the types of apnea. During obstructive apnea, an individual makes respiratory efforts, but no airflow occurs because of upper airway obstruction. Central apnea is an interruption in both airflow and breathing effort. Mixed apneas have both central and obstructive components. A typical mixed event begins with a central apnea, which is followed immediately by one or more obstructed breaths.

Hypopneas are episodes of shallow breathing during which airflow is decreased by at least 50%. They are usually accompanied by some degree of oxygen desaturation, which can be minor and transient. Like apnea, hypopnea is subdivided into obstructive, central, and mixed. Obstructive hypopneas are episodes of partial upper airway obstruction. Respiratory efforts occur, but airflow is reduced. In central hypopnea, breathing effort and airflow are both decreased. Mixed hypopneas have both central and obstructive components.

In adults, episodes of disordered breathing must last 10 seconds or more before being considered an apnea or hypopnea. Normal resting respiratory rates in children are faster than those in adults, and children have a smaller functional residual capacity and a more compliant chest wall. As a result, children undergo oxygen desaturation more rapidly than adults whenever airflow is interrupted. A definition of apnea or hypopnea requiring that an event last 10 seconds or more before being considered significant is somewhat arbitrary and does not take into account the physiologic differences between adults and children. Consequently, pediatric sleep centers use different duration criteria for labeling events such as apnea or hypopnea. In children, if obstruction occurs with 2 or more consecutive breaths, the event can be called an apnea or hypopnea, even if it lasts less than 10 seconds.


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