NAPLES, Fla.—Sleep studies to detect obstructive sleep apnea can be performed in the patient’s home—although the convenience and lower costs for performing the tests outside the laboratory are offset by a loss of accuracy.
Explore this issue:April 2006
“The lower cost of home sleep studies makes them a viable screening tool for patients with suspected obstructive sleep apnea,” said Mark Ghegan, MD, a researcher in the Department of Otolaryngology–Head and Neck Surgery at the Medical University of South Carolina in Charleston, in a presentation here at the meeting of the Southern Section of the Triological Society.
Dr. Ghegan, however, did note that laboratory polysomnography sleep studies remain the gold standard in the diagnosis of major sleep disorders.
A Widespread Problem
“The problem of obstructive sleep apnea is immense,” Dr. Ghegan said. “One in five Americans is estimated to be afflicted with the disorder. On average, a person with obstructive sleep apnea has an event five times an hour.”
Obstructive sleep apnea can cause excessive daytime sleepiness in people who have the disorder. The market for products to combat the disorder totals in the neighborhood of $1.4 billion a year.
The public and the medical profession have become more and more aware of the disorder, Dr. Ghegan said. However, the only confirmatory test is a polysomnography procedure done in the laboratory.
He set out to perform a meta-analysis of studies done to test whether home sleep analysis equipment and procedures are useful tools when compared to the laboratory settings—noting that both the laboratory and the home settings have advantages and disadvantages.
Measuring Respiratory Distress
The primary goal of the meta-analysis was to compare the respiratory distress index (RDI) in the home studies with the laboratory studies.
The American Academy of Sleep Medicine rates the average number of obstructive sleep apnea events per hour as the respiratory distress index. An RDI of 0 to 5 is normal, 5 to 20 is mild, 20 to 40 is moderate, and over 40 is considered severe. An apnea event must last at least 10 seconds to be considered an event.
It is not uncommon to see RDIs well above 40. In some cases RDIs were well above 100, with events lasting as long as 90 to 120 seconds. During these bouts of apnea, blood oxygen saturation can fall well below normal levels.
Lab Setting Allows for Other Tests
“The laboratory setting remains the gold standard,” said Dr. Ghegan, because in the laboratory setting doctors may conduct other studies, an electroencephalogram (EEG), and other brain wave measurements. The laboratory setting, he noted, also allows doctors to perform nasal airflow analyses and oxygen saturation studies.