Device Puts Sleep Apnea Diagnosis Hurdles to Rest

Originally Published MDDI June 2002

MEDICAL DESIGN EXCELLENCE AWARDS 2002

SleepStrip Disposable Sleep Apnea Screener

Submitted and manufactured by SLP Ltd. (Tel Aviv, Israel)

Studies indicate that in the United States alone more than 10 million cases of sleep apnea remain undiagnosed. The high cost, complexity, inconvenience, and low availability of sleep studies are some of the reasons why this condition so often isn't tested for and treated. Many times throughout the night, sufferers of sleep apnea stop breathing for more than 10 seconds at a time or experience significant decreases in respiratory amplitude, both of which may lead to excessive daytime fatigue, hypertension, cardiovascular disease, and other disorders.

The SleepStrip Disposable Sleep Apnea Screener was designed by Noam Hadas, then R&D manager of SLP Ltd., and Peretz Lavie, a professor who heads the Technion Sleep Disorder Center, to make diagnosis of the disorder accessible to everyone.

"Our test is much like a home pregnancy test in that you will be able to buy it at the drugstore, take the test yourself, and get the results quickly," says Hadas, now SLP CEO. (The test is currently available only by prescription.) Unlike other sleep-monitoring devices, "SLP's product is self-contained; there is no additional hardware, software, or handling." Most importantly, the test costs less than $50.

The single-use, miniature sleep respiration screener consists of a plastic strip measuring 6 in. by 1 in. that the patient attaches under his nose, like a Band-Aid, and a gel that activates the device. During the first 20 minutes of use, the device calculates the patient's normal breathing pattern. Then, for the next five hours, it continues to monitor and analyze respiratory flow patterns in real time, counting the number of times each hour that the patient stops breathing or the amplitude is reduced. The device then determines the average count per hour and sends that value to the display. SleepStrip's ability to measure data in real time and deliver results immediately sets it apart from all other sleep-monitoring devices, according to SLP. Those latter monitors record all data, which then must be downloaded and analyzed—a time-consuming, expensive process.

The SleepStrip's electrochemical display contains six silvery-white dots that turn a dark gray or black after use, indicating the presence and severity level of sleep apnea. While the device is capable of providing a diagnosis to patients directly, due to current regulatory requirements the display presents a binary code that only physicians can interpret. Still, testing is now available to millions of people who could not have been diagnosed before—owing either to the cost or the logistics involved in being tested at a sleep clinic.

"The biggest challenge we faced was in getting the price down," Hadas notes. "SleepStrip doesn't use any new technologies—it uses the same type of sensor and the same type of algorithm as devices used in sleep clinics. The difference is how we collect data. We rely on real-time data analysis rather than on storing every piece of data collected during the night—that would have required a huge memory, and a download and analysis period. We tested more than 30 software versions before finding one that could score specific respiration patterns in real time to our satisfaction and deliver an analysis as soon as the study was over. The software is written in machine code to save memory.

"It was also very difficult to manufacture a low-cost display that would stay visible without power," Hadas adds. "We developed a permanent electrochemical display that, once activated, can be disconnected from the circuit and still remain readable indefinitely. We use Chinese components and production in the East to keep costs down."

SLP now plans to apply its proprietary technology of integrating a physiological sensor, real-time data processing, and a permanent display element in a low-cost, disposable medical test to two more sleep-monitoring devices that will screen periodic limb movement disorder and sleep bruxism. Millions of consumers will simply be grateful that, as a result of SLP's efforts, they should soon be able to enjoy a good night's sleep.

Copyright ©2002 Medical Device & Diagnostic Industry