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Learning Objectives
The student will be able to use clinical and polysomnographic data to differentiate patients showing obstructive sleep apnea, central sleep apnea, complex sleep apnea, and sleep-related hypoventilation/hypoxemic syndromes.
The student will be able to describe the pathophysiological mechanisms underlying each of these classes of sleep-related breathing disorders.
The student will be able to summarize the most effective therapies for each type of sleep-related breathing disorder.
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OBSTRUCTIVE SLEEP APNEA SYNDROMES
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The three major types of sleep-related breathing disorders are obstructive sleep apnea syndrome (OSAS), central sleep apnea syndrome, and sleep-related hypoventilation hypoxemic syndromes. Of these, OSAS is the most common type of sleep-related breathing disorder and is characterized by repetitive episodes of complete apnea or partial hypopnea caused by upper airway obstruction. Episodes last at least 10 seconds, occur during sleep, are usually associated with decreased Sao2%, and are terminated by brief arousals. OSAS is associated not only with neurocognitive dysfunction but also with increased cardiovascular morbidity and mortality.
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OSAS is relatively common, with a prevalence of 4% in men and 2% in women when defined by an apnea-hypopnea index (AHI) ≥5 events/h plus a complaint of excessive daytime sleepiness. Features predisposing to OSAS include male sex, age, obesity, menopausal state, race, craniofacial abnormalities with decreased orohypopharyngeal space, endocrine disorders, and certain congenital disorders (Table 25.1).
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The high male-to-female prevalence ratio for OSAS of 2:1 is attributed to the protective effect of female sex hormones predominant in premenopausal women; the prevalence of OSAS in women triples after menopause and is reduced to premenopausal levels with hormone replacement therapy. Meanwhile, increased body mass index (BMI) is the major risk factor for OSAS in adults (Chap. 12). There appears to be a linear relationship between BMI and OSAS severity: Each 10% increase in body weight results in a 30% increase in AHI. On the other hand, adenotonsillar hypertrophy is the major cause of OSAS in children. For patients who are not overweight or obese, certain craniofacial features (eg, retrognathia, long uvula) can predispose to OSAS. Increased nasal resistance from rhinitis or a deviated nasal septum can worsen airway collapse due to the greater inspiratory effort required to breathe through such nasal passages. Asians may be at a higher risk for OSAS due to crowding of the posterior ...