Obstructive sleep apnea (OSA) is a highly prevalent disease characterized by recurrent episodes of upper airway obstruction that result in recurrent arousals and episodic oxyhemoglobin desaturations during sleep. Significant clinical consequences of the disorder cover a wide spectrum, including daytime hypersomnolence, neurocognitive dysfunction, cardiovascular disease, metabolic dysfunction, and cor pulmonale.

The major risk factors for the disorder include obesity, male gender, and age. Current understanding of the pathophysiologic basis of the disorder suggests that a balance of anatomically imposed mechanical loads and compensatory neuromuscular responses are important in maintaining upper airway patency during sleep.

OSA develops in the presence of both elevated mechanical loads on the upper airway and defects in compensatory neuromuscular responses. A sleep history and physical examination is important in identification of patients and appropriate referral for polysomnography.

Understanding nuances in the spectrum of presenting complaints and polysomnography correlates are important for diagnostic and therapeutic approaches. Knowledge of common patterns of OSA may help to identify patients and guide therapy.

Key Words: critical pressure • diagnosis • obstructive sleep apnea • pathophysiology

_{Susheel P. Patil, MD, PhD; Hartmut Schneider, MD, PhD; Alan R. Schwartz, MD and Philip L. Smith, MD}

From the Department of Medicine, Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, MD.

Correspondence to: Susheel P. Patil, MD, PhD, Johns Hopkins Sleep Disorders Center, Asthma and Allergy Building, 5501 Hopkins Bayview Circle, Room 4B.41, Baltimore, MD 21224

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