Sleep apnea can be diagnosed without sleep lab

By Amy Norton

NEW YORK (Reuters Health) - Some people with the breathing disorder sleep apnea can be diagnosed and treated without going through overnight studies in a sleep lab, researchers report.

Their findings, based on a study of 68 patients, suggest that people with strong signs of obstructive sleep apnea (OSA) can go without the extensive, costly sleep-clinic tests recommended for diagnosing the disorder.

In OSA, soft tissues in the throat temporarily collapse during sleep, causing repeated stops and starts in breathing. Loud snoring and daytime sleepiness can be tell-tale symptoms, but experts recommend that people undergo overnight polysomnography in a sleep lab to diagnose the condition and to initially manage treatment.

In the new study, published in the Annals of Internal Medicine, researchers found that simpler home testing can work just as well for patients strongly suspected of having OSA.

All 68 study patients had at least a 90 percent chance of having the disorder based on their signs and symptoms and on a home test that measures oxygen in the blood.

The researchers then randomly assigned them to have overnight polysomnography -- which measures breathing, heart rate and brain activity during sleep -- or to start treatment right away with continuous positive airway pressure, or CPAP.

CPAP is considered the most effective treatment for OSA. The therapy involves wearing a facemask through which the CPAP device delivers pressurized air to keep the airways open during sleep. Normally, overnight testing is recommended both to confirm sleep apnea and to set the CPAP device at the right pressure level.

In this study, however, patients who started treatment immediately were given auto-CPAP, a "smart" device that automatically makes pressure adjustments during the night.

After three months, the researchers found, these patients were doing just as well as those who went through sleep studies before starting CPAP. They had similar improvements in the number of breathing problems during the night -- as measured by the CPAP device -- and in daytime sleepiness.

A potential risk of forgoing sleep-clinic studies is misdiagnosis, the researchers say. On the other hand, if someone is very likely to have OSA but would have to wait longer than two or three weeks for polysomnography, the at-home approach might be the better choice, according to Dr. C. Frank Ryan, a professor of medicine at the University of British Columbia and the study's senior author.

People with moderate to severe OSA are at risk of cardiovascular disease and, because of drowsiness, car accidents, Ryan pointed out. "There is a potential benefit in starting treatment as quickly as possible," he told Reuters Health.

The study also found that patients who started auto-CPAP right away were ultimately more compliant with their treatment, using the CPAP device for more hours per night.

It's not clear why this was, but the shorter wait for treatment might be one reason, Ryan speculated.

When asked, only 6 percent of patients in this group said they would have preferred having sleep studies; in contrast, Ryan noted, 62 percent of the polysomnography group said they would have opted for the home-based approach.

SOURCE: Annals of Internal Medicine, February 6, 2007.