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DEFINITION

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Obstructive sleep apnea (OSA) is a syndrome of repetitive upper-airway obstruction during sleep. It is defined as five or more episodes per hour during sleep of complete airflow cessation (apnea) or a partial airflow reduction of 30%–99% (hypopnea) each lasting greater than 10 seconds, despite continued respiratory effort, and accompanied by a 4% decrease in oxygen saturation. Common associated symptoms include daytime sleepiness, impaired concentration, recurrent awakenings and restless sleep, and gasping/choking sensations during sleep. The condition is described by the Apnea-Hypopnea Index (AHI) that is derived from the total number of apneas and hypopneas per hour of sleep. The American Academy of Sleep Medicine defines mild OSA as AHI 5–15, moderate OSA as AHI 15–30, and severe OSA as AHI > 30.

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The true prevalence of OSA in the general population is unknown but increasing. Originally thought to range from 2% to 5% of the population, The Centers for Disease Control and Prevention in 2002 cited a prevalence of 22% of the male population and 9% of the female population. Among selected surgical populations the prevalence may range up to 80%. Importantly, the vast majority of patients affected by OSA are not yet diagnosed when they present for surgery. In one study of 170 patients about to undergo surgery, only 15% had previously been diagnosed with sleep apnea but preoperative testing revealed 76% had the disorder.

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PATHOPHYSIOLOGY

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Obstructive sleep apnea results from several factors, including soft-tissue and skeletal features that predispose individuals to airway narrowing during sleep. The upper-airway collapse that occurs during an episode of obstructive sleep apnea is a result of decreased neuromuscular tone during sleep, most prominent during the hypotonic rapid-eye-movement (REM) sleep stage. Common physical features present in those with OSA include retrognathia, soft palate enlargement, tonsillar hypertrophy, and increased neck circumference associated with increased amounts of adipose tissue in their oral and pharyngeal tissues. Deposition of fat in the lateral walls decreases the size of the airway and changes the shape of the oropharynx into an ellipse with a short transverse and long anteroposterior axis. Among the many risk factors associated with OSA, obesity, male gender, and older age predominate.

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Consequences of OSA are numerous and potentially life-threatening. Several studies have revealed complications to include systemic and pulmonary hypertension, left and right ventricular hypertrophy, cardiomyopathy, dysrhythmias such as atrial fibrillation, MI, stroke, insulin resistance and diabetes, and both acute and chronic cognitive impairment leading to an increased risk of motor vehicle accidents. Because of these significant risks, treatment is recommended for patients with moderate or severe disease. Treatment depends partly on the severity of the sleep-disordered breathing, but the consensus is that patients with moderate or severe apnea should be treated with continuous positive airway pressure (CPAP) during sleep. Other treatments include oral appliances, corrective surgery, and conservative measures for those with mild OSA such as weight loss, avoidance of alcohol before bedtime, and ...

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