Obstructive Sleep Apnea Hypopnea 379
elevated arousal index (arousal index greater th an 30) or reduced stages in deep sleep (e.g.,
percentage stage N3 [slow-wave sleep] less than 5%).
Diagnostic Features
Obstructive sleep apnea hypopnea is the most  common breathing-related sleep disorder.
It is characterized by repeated episodes of upper (pharyngeal) airw ay obstruction (apneas
and hypopneas) during sleep. Apnea  refers to the total absence of airflow, and hypopnea  re-
fers to a reduction in airflow. Each apnea or  hypopnea represents a reduction in breathing
of at least 10 seconds in duration in adults or two missed breaths in children and is typi-
cally associated with drops in oxygen saturation  of 3% or greater and/or an electroenceph-
alographic arousal. Both sleep-related (nocturnal) and wake-time symptoms are common.
The cardinal symptoms of obstructive sleep apnea hypopnea are snoring and daytime
sleepiness. 
Obstructive sleep apnea hypopnea in adults  is diagnosed on the basis of polysom-
nographic findings and symptoms. The diagnosis is based on symptoms of 1) nocturnal
breathing disturbances (i.e., snoring, snorti ng/gasping, breathing pauses during sleep), or
2) daytime sleepiness, fatigue, or unrefreshi ng sleep despite suffic ient opportunities to
sleep that are not better explained by another mental disorder and not attributable to an-
other medical condition, along with 3) eviden ce by polysomnography of five or more ob-
structive apneas or hypopneas per hour of sleep (Criterion A1). Diagnosis can be made in