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Pulmonology - Obstructive Sleep Apnea - Fast Facts | NEJM Resident 360

Obstructive sleep apnea (OSA) is a disorder caused by episodic airway obstruction (apnea) or partial upper-airway collapse with reduced airflow (hypopnea) during sleep. Individuals with OSA experience frequent arousals from sleep with fragmentation of the sleep cycle and are at risk for nocturnal hypoxemia and hypercapnia. Patients with OSA may present with daytime sleepiness, a lack of refreshing sleep, or waking up from sleep gasping for air. Sleep partners may report bothersome snoring.

OSA is common; it is an independent risk factor for occupational and motor vehicle accidents and can reduce quality of life. Some evidence suggests that OSA is associated with increased cardiovascular events and mortality. Patients in certain occupations (e.g., commercial truck drivers) and those in recent motor vehicle accidents should be screened for symptoms of OSA. Patients with medical comorbidity, such as heart disease and symptoms of daytime drowsiness, also should be screened for OSA.

Assessment

Presentation: Obesity is the biggest risk factor for OSA and associated with >50% of cases. Individuals with a BMI >30 kg/m² and large neck circumference (>16 inches in women, >17 inches in men) have elevated risks and should be screened for OSA. More than 10% weight gain is associated with a sixfold increase in developing clinically significant OSA.

Other signs and symptoms that should trigger suspicions of OSA include:

• loud or irregular snoring

• daytime sleepiness

• unrefreshing sleep regardless of sleep duration

• increased fatigue when patient is sedentary

• nocturia

• choking and gasping in sleep

• dry mouth on awakening

• morning headaches

• body-mass index >30

• crowded oropharynx

• increased neck circumference (men, >17 in. [43.2 cm];
  women, >16 in. [38.1 cm])

Medical comorbidity: Certain comorbid conditions should also prompt evaluation for OSA in a patient who reports unrefreshing sleep or daytime somnolence. Coexisting conditions that are associated with increased prevalence of OSA include heart failure, atrial fibrillation, treatment-refractory hypertension, type 2 diabetes, metabolic syndrome, nocturnal dysrhythmias, stroke, hypothyroidism, acromegaly, and pulmonary hypertension.

Screening: The following screening tools can be used to screen for sleep disorders and their consequences.

• The STOP-Bang Questionnaire asks the patient to answer eight questions about Snoring, Tiredness, Observed apneas, elevated blood Pressure, BMI >35 kg/m², Age, Neck circumference, and Gender to determine the pretest probability of OSA. A score of 5 or greater is associated with high risk of OSA.

• The Epworth Sleepiness Scale is a patient questionnaire for measuring daytime sleepiness. Patients are asked to score their risk of falling asleep in certain situations. A score >10 requires further assessment, while a score >16 is associated with a high probability of sleep-disordered breathing.

Physical examination should include evaluation for signs of airway narrowing (e.g., enlarged neck circumference [>17 inches in men and >15 inches in women]), nasal septal deviation or nasal polyps, retrognathia, high-arched palate, macroglossia, and tonsillar hypertrophy.

Investigations

Polysomnography: A definitive diagnosis of OSA is made by overnight polysomnography, which uses electroencephalogram, eye movements, nasal/oral air flow, and muscular movements to determine an apnea–hypopnea index (AHI), defined as the number of apneic/hypopneic events that occur per hour of sleep. Based on the polysomnogram, the severity of OSA can be classified as follows:

Obstructive Sleep Apnea Severity and the Apnea–Hypopnea Index

| Apnea Severity Rating | Apnea–Hypopnea Index (AHI)
(events/hour of sleep) | | --- | --- | | Normal | AHI <5 | | Mild | AHI ≥5 but <15 | | Moderate | AHI ≥15 but <30 | | Severe | AHI ≥30 |

Treatment

Treatment for OSA is recommended in patients with an AHI of at least 15 (moderate disease) who complain of daytime somnolence, impaired cognition, mood disturbance, or other symptoms of unrefreshing sleep. OSA should also be considered in patients who have coexisting conditions such as hypertension, ischemic cardiac disease, or stroke.

• Lifestyle changes: Treatment for OSA should include discussion about lifestyle changes such as weight reduction and exercise.

• Continuous positive airway pressure (CPAP) therapy: CPAP is the definitive treatment for OSA. CPAP has been shown to improve sleep and reduce daytime sleepiness, and has been associated with reduction in motor vehicle accidents and cardiovascular events. (See a video demonstration of CPAP.) Although CPAP is the gold standard for the treatment of OSA, many patients find the device intolerable. Other interventions to consider in difficult-to-treat cases include:

  • positional therapy (e.g., avoiding supine sleep), oral mandibular advancement devices

  • surgical intervention

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