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Key Clinical Questions
What are the key distinguishing features between obstructive and central sleep apnea?
What are the consequences of untreated sleep apnea?
What are the indications for inpatient therapy for sleep apnea?
How should patients with suspected sleep apnea be managed at hospital discharge?
What is obesity hypoventilation syndrome and how is it best treated?
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Sleep apnea is defined by repeated transient cessations of respiration during sleep. The most common type of this disorder, obstructive sleep apnea (OSA), affects between 5% and 15% of middle-aged and older adults. The burden of disease in the hospitalized patient is likely to be even greater than that of the general population because inpatients carry many disorders that have been associated with OSA, including obesity, congestive heart failure, coronary artery disease, hypertension, stroke, and diabetes. Epidemiologic data suggest that the majority of patients with sleep apnea are undiagnosed; in 2004, national hospital discharge codes revealed fewer than 300,000 cases of sleep apnea among almost 35 million inpatient stays, yielding a prevalence of identified disease of less than 1%.
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Although sleep apnea by itself is rarely a primary indication for hospitalization, recent evidence suggests that inpatient management of this disease needs to improve. Less than 6% of those identified as having sleep apnea in the 2004 National Hospital Discharge Survey received therapy with continuous positive airway pressure (CPAP) while in the hospital. Hospital Medicine physicians should identify and appropriately treat OSA patients. The key to identifying the possible presence of sleep apnea depends largely on an appreciation of risk factors and clinical features. In 2008, Goring and Collop showed that almost 80% of patients with suspected sleep apnea referred for a sleep study after an inpatient hospitalization were confirmed to have OSA. Therefore, inpatient identification and referral for evaluation can improve diagnosis rates and reduce the percentage of affected patients left untreated. This chapter will review the fundamentals of sleep apnea, address the management of patients with stable sleep apnea in the inpatient setting, delineate the necessity of preoperative screening in at-risk patients, and identify which patients should undergo further testing.
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Sleep-disordered breathing includes three related classes of diseases: OSA, central sleep apnea (CSA), and sleep-related hypoventilation—although as many as 90% of all cases are OSA. The distinction between OSA and the other categories is an important one as the treatment options and responses to therapy are quite different. Obesity hypoventilation syndrome (OHS) is a condition in which obese patients develop diurnal hypercapnia and hypoxemia in the absence of a causal pulmonary or neurologic disorder; up to 90% of these patients have OSA, though the causative association has yet to be proven.
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OBSTRUCTIVE SLEEP APNEA
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The upper airway is a compliant structure susceptible to collapse. Complex neurologic and musculoskeletal interactions cause a decrease in the cross-sectional area of the upper airway during sleep, which ...