As reported previously in ENToday, as many as 18 million Americans might have obstructive sleep apnea (OSA) with an apnea-hypopnea index (AHI) > 5.0 events per hour of sleep, according to the National Commission on Sleep Disorders Research report, Wake up America: A National Sleep Alert. The National Sleep Foundation’s 2004 Sleep in America poll found that almost one in five preschoolers and school-age children snore, which can be an indication of sleep apnea.
Explore This IssueOctober 2007
Insomnolence due to OSA may lead adults to sit and seethe in traffic jams, quarrel with other people, or overeat, and is suspected to increase the risk for daytime learning problems, poor school performance, daytime sleepiness, and hyperactivity in children. Effectively screening for OSA, as well as improving or resolving certain comorbidities of OSA, is becoming increasingly important for sleep-deprived adults and children.
Screening for OSA
Polysomnography (PSG) has long been considered the gold standard for the diagnosis of OSA, but its use is limited by the availability of sleep centers and the costs of the tests, stated Jordan C. Stern, MD, of the New York Otolaryngology Group in his presentation, A New Device for Home Screening of Obstructive Sleep Apnea Using Holter Oximetry, delivered at the Combined Otolaryngology Spring Meeting in April. Other screening tests have been proposed over the past 20 years, ranging from simple overnight pulse oximetry to more complex multiple channel home devices.1 Previous studies have determined that single-lead electrocardiogram (ECG) recordings from sleep study patients can detect OSA with great sensitivity and specificity in the laboratory setting.2,3,4
ENTs are confronted daily with patients presenting with the signs and symptoms of OSA, said Dr. Stern. Many patients do not want to go through the trouble of sleeping in a lab; hence, a reliable, inexpensive, portable, and easy-to-use at home screening device would be invaluable for both ENTs and their patients.
During his presentation, Dr. Stern described the use of two new devices to screen for OSA in the unattended home setting: (1) the Holter apnea monitor (continuous ambulatory ECG recording) and (2) the Holter oximeter (both continuous ECG recording and pulse oximetry). The underlying technology in both devices is the same; each consists of a small portable digital recording device connected to chest electrodes. The Holter oximeter has an additional pulse oximetry finger probe.
The Holter oximeter uses the same software to analyze the continuous ECG signal, as well as data from the continuous pulse oximetry, and produces two outputs. The first output is an epoch-by-epoch sequence of annotations of normal or sleep-disordered breathing (SDB). The second output provides an estimate of the AHI, derived from the epoch-by-epoch annotations. An estimated AHI was derived from the per-epoch classification by counting the average number of detected apnea segments per hour of sleep and automatically applying an appropriate threshold.