New Guideline for Sleep Apnea Diagnosis

Pauline Anderson

August 11, 2014

Patients with unexplained daytime sleepiness should undergo a sleep study, preferably polysomnography (PSG), according to new recommendations developed by the American College of Physicians.

However, these recommendations for diagnosing obstructive sleep apnea (OSA), based in part on a literature search, are weak, and the quality of the evidence was graded as low or moderate, according to the authors.

Recommendations are typically weak if there are no related randomized controlled trials, the studies assessing the topic weren't robust, or the data weren't reproducible, said David Fleming, MD, president, American College of Physicians, and chair, medicine, University of Missouri, Columbia.

"I think this guideline begs the question of whether we need more research in this area, and clearly we do. But this is the state of the science as we know it, and we can only use data that's available," he told Medscape Medical News.

The new recommendations, prepared by the ACP Clinical Guidelines Committee led by Amir Qaseem, MD, PhD, were published in the August 5 issue of Annals of Internal Medicine.

Obesity Risk

OSA is caused by an obstruction of the upper airway during sleep that results in hypopnea (reduced airflow) or apnea (complete airflow cessation). In addition to daytime sleepiness, clinical symptoms include unrefreshing sleep, fatigue, insomnia, and snoring. The condition is associated with adverse clinical outcomes, including cardiovascular disease, hypertension, cognitive impairment, and metabolic abnormalities.

The reviewers searched MEDLINE, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews. They evaluated the studies for all-cause mortality, cardiovascular mortality, nonfatal cardiovascular disease, stroke, hypertension, type 2 diabetes, postsurgical outcomes, and quality of life. Most studies excluded patients with comorbid conditions, such as chronic lung diseases, congestive heart failure, and neurologic disorders.

The recommendation for a sleep study in patients with unexplained daytime sleepiness was based on low-quality evidence. The reviewers recommend that the physician assessment include evaluation of the risk factors and common presenting symptoms for OSA. The best-documented risk factor for OSA is obesity.

The recommendation that PSG be used to diagnose patients suspected of having OSA was based on medium-quality evidence. PSG measures or estimates the apnea-hypopnea index (AHI), which is the number of apnea or hypopnea events per hour during sleep.

The AHI is used to assess the severity of OSA as well as to diagnose it. The American Academy of Sleep Medicine sets a threshold of 15 events per hour with or without symptoms or 5 events per hour with symptoms such as daytime somnolence and fatigue.

Although PSG, performed in a sleep laboratory, is the "gold standard" for diagnosing OSA, it is resource-intensive and expensive, and patients must spend the night under observation. In the absence of PSG, the reviewers recommend portable monitors, which also assess AHI.

Portable Devices

There are several types of portable devices: type II, III, and IV (type 1 is used in a facility and isn't portable). These vary in the number of channels — from 7 or more in type II to 1 - 3 in type IV — with those having more channels performing better than those with fewer channels, according to the review. Type II monitors measure AHI while types III and IV estimate AHI.

The overall quality of the evidence for all portable monitors was moderate, according to the authors. No study directly compared the different monitors with each other. Compared with PSG, all monitor types had a wide range of differences in AHI estimates.

There was indirect evidence that type III monitors performed better than type IV monitors in predicting AHI scores suggestive of OSA. Type IV monitors have an important limitation in that they're unable to distinguish obstructive from central sleep apnea.

Central sleep apnea results from a temporary failure of the brain to send signals to breathe. Patients with cardiac, respiratory or neurologic disease may be at greater risk of central sleep apnea. In these patients, portable monitors for diagnosis are not recommended. said the authors.

Continuous positive airway pressure (CPAP) devices may also be contraindicated in patients with central sleep apnea.

Although the portable monitors "are a reasonable alternative" to a sleep lab, they have some drawbacks, commented Dr. Fleming. Patients need to understand how they work, the leads can fall off the devices, and the recordings need to be correctly interpreted. As well, he said, the monitor "will tell you if there is a problem with apnea, but it may not tell you what kind of apnea and therefore which kind of treatment" to pursue.

If a monitor picks up a problem, a patient might want to get a full study in the sleep lab, he said.

Clinical Insight

"Much of this is clinical insight; it's just talking to the patient, doing an examination, looking at comorbidities," said Dr. Fleming. "If I have a patient with a BMI [body mass index] of 35 to 40 with type 2 diabetes and hypertension, and his wife is complaining that he is snoring all time and is drowsy during day and keeps falling asleep at dinner, to me the diagnosis has been made."

The "key," added Dr. Fleming, is not making the diagnosis but rather getting the appropriate treatment. "It's getting to what the patient can tolerate (in terms of CPAP [continuous positive airway pressure] or other nighttime device), and getting them to where they can actually start exercising and to where maybe they will start losing weight."

Evidence was insufficient to determine the utility of most questionnaires in screening for OSA, said the reviewers. They noted that questionnaires may not be applicable to the general population because they include subjective questions about sleepiness and not all patients report this symptom.

The evidence was also insufficient to determine the effectiveness of "phased testing" for the diagnosis of OSA. Phased testing might involve a confirmatory test one night and titration of a pressure device the next, said Dr. Fleming.

There's also insufficient evidence for the utility of preoperative screening for OSA to improve postsurgical outcomes, said the authors.

These new recommendations follow on the heels of others developed by the ACP last year. At that time, the College recommended that all overweight and obese patients diagnosed with OSA be encouraged to lose weight, that CPAP treatment be used as initial therapy for OSA patients and that mandibular advancement devices may be an alternative to CPAP for patients who prefer these devices or who are adverse to CPAP.

Dr. Qaseem has no disclosed relevant financial relationships.

Ann Intern Med. 2014;161:210-220.

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