Order blood tests. Routine blood tests do not support an OSA diagnosis, but they help rule out or identify other conditions associated or mimicking OSA, such as anemia, hypothyroidism, diabetes, liver disease, and kidney disease. Suggested labs include a comprehensive metabolic profile, complete blood count, and thyroid-stimulating hormone test.
Sleep studies are needed for a definitive diagnosis
Conducted overnight in a sleep lab, polysomnography (PSG) uses respiratory effort, respiratory air flow, and peripheral oximetry to identify and quantify episodes of apnea and hypopnea (reported as the apnea-hypopnea index, or AHI). PSG also records brain electrical activity (electroencephalogram), heart rhythm (electrocardiogram), eye movement (electro-oculogram), and muscle activation (electromyogram)—studies used to identify other sleep disorders, such as restless leg syndrome, narcolepsy, parasomnias, and disturbances in rapid-eye movement
(REM) sleep.
Home monitoring. For patients who are unable or unwilling to undergo an overnight sleep study, home portable monitoring is a less expensive alternative. The monitor—a small wireless device—provides data for calculating the AHI and the presence and degree of oxygen desaturation.14 Unlike PSG, which can identify the amount of pressure needed for continuous positive airway pressure (CPAP) therapy, findings from a portable monitor are not sufficient to rule out other sleep disorders to determine whether CPAP is required.15
Evaluating daytime sleepiness. Several tools have been used to evaluate daytime sleepiness. The Epworth Sleepiness Scale (ESS), a quick 8-item screening questionnaire, determines the average person’s level of sleepiness during the day. It ranges from 0 to 24 points, with 10 being normal. Although the ESS has been used extensively in OSA research, recent studies found that it has a low sensitivity (54%) and specificity (57%) for scores >10 and does not correlate well with hypopnea and apnea measurements.16,17
Two additional tools, the Berlin and STOP questionnaires, can also be used to screen for OSA. Both questionnaires have about a 50% positive predictive value and a 70% negative predictive value.18,19
Diagnosing and classifying OSA
Diagnostic criteria developed by the American Academy of Sleep Medicine (AASM) are based on reported and observed symptoms and PSG recordings of hypopnea and apneic episodes. Of the 4 criteria (A through D), patients must meet either A, B, and D or C and D (TABLE 2).15
The AASM further classifies OSA as mild, moderate, or severe (TABLE 3)15 based on the AHI as well as on clinical findings, including oxygen desaturation and arrhythmias. Patients with severe OSA have excessive daytime sleepiness (EDS) that interferes with their normal activities, 15 as well as severe oxygen desaturation, moderate to severe cardiac arrhythmias, and significant risk for hypertension, MI, stroke, and cor pulmonale.
CASE 1 An examination of Mr. M’s upper airway anatomy reveals a neck circumference of 44 cm and normal oropharynx. The results of his lab tests were only significant for elevated blood sugar (234 mg/dL) and glycosylated hemoglobin (9.2%). Because he presents with classic symptoms of OSA, he receives a referral for PSG. He is found to have an AHI of 49, consistent with severe sleep apnea.
CASE 2 A system review of Ms. C finds no fever, nausea, vomiting, weakness, vision changes, or neurological symptoms. A Patient Health Questionnaire-9 (depression screen) is normal, as are her lab tests and a brain MRI with and without contrast. After an extensive work-up for headaches finds nothing, OSA is considered, in light of her daytime sleepiness—and she, too, is referred for PSG. This patient has moderate OSA, with an AHI of 27.
Initiating treatment: What’s best?
Ideally, treatment of OSA would reverse EDS and fatigue, restore full cognitive function, reduce the risk of accidents associated with OSA, and minimize its harmful cardiovascular and pulmonary effects. In fact, while OSA can be managed and its effects ameliorated, all available treatments have limitations and a cure remains elusive.
Let patients know that our understanding of OSA is limited, that treatment may not reverse or eliminate all the risks associated with this condition, and that compliance can be challenging. You can also tell them that, while more and better studies are needed, several modalities have been found to successfully treat OSA.
What to expect from lifestyle modification
Recommend lifestyle changes, such as weight loss, regular exercise early in the day, greater emphasis on sleep hygiene (eg, using the bed only for sleeping and sexual activity), and avoidance of sedating drugs and alcohol for patients with OSA.20,21
The beneficial effect of weight loss on OSA has been demonstrated in studies of both bariatric surgery and conventional weight loss therapies.21-23 While early studies of bariatric surgery were often limited by small size, ambiguous classification of OSA, and selection and follow-up biases, more recent trials show that while OSA symptoms frequently improve postoperatively, the disorder typically persists despite significant reductions in both BMI and AHI.24 Weight reduction should be strongly encouraged for obese patients, however, not only to improve OSA symptoms, but also to reduce the risk for other diseases.