Obstructive Sleep Apnea of Obese Adults

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Abstract
OBSTRUCTIVE sleep apnea (OSA) is a common disordered breathing during sleep in humans. Polysomonographic recordings of sleep stages, respiration, and oxygenation reveal characteristics of OSA (fig. 1). Complete cessation of airflow for more than 10 s (apnea) or airflow reduction more than 50% (hypopnea) despite continuing breathing efforts results in hypoxemia and hypercapnia. This obstructive apnea or hypopnea is caused by complete or partial closure of the pharyngeal airway.1 The apnea or hypopnea is usually terminated in association with cortical arousal, opening the pharyngeal airway. Breathing is reestablished with loud snoring, normalizing oxygenation, and often overshooting ventilation. OSA patients repeat the obstructive apnea or hypopnea, resulting in blood gas oscillation and sleep fragmentation. Clinical diagnosis of OSA is made when frequency of apnea and/or hypopnea per hour of sleep (apnea–hypopnea index [AHI]) is greater than five in adults. Severity of OSA is determined by the AHI: mild OSA = AHI 6–20 h−1, moderate OSA = AHI 21–40 h−1, and severe OSA = AHI > 40 h−1.