A Highly Accurate Sleep Apnea Test on Your Smartphone
There are already several home sleep apnea tests available, but some are costly and inconvenient; that could change with the development of a new smart phone app from the University of Washington (UW), according to a news release by Dr. Nathaniel F. Watson, Md, MSc, professor of neurology and co-director of the UW Medicine Sleep Center. The study uses a smartphone to wirelessly test for sleep apnea events in a person’s own bedroom. Unlike other home sleep apnea tests in use today, ApneaApp uses inaudible sound waves emanating from the phone’s speakers to track breathing patterns without needing special equipment or sensors attached to the body.
The clinical study was presented at the MobiSys 2015 conference in May. It’s been appropriately called the ApneaApp, because it can identify signs of sleep apnea as accurately as a polysomnography test, which is 98% accurate. For those of you who don’t know, the polysomnograph is the gold standard among sleep apnea tests, which tests for a disease that affects roughly 1 in 13 Americans. The polysomnograph, however, is much more costly and inconvenient, since it requires an overnight stay in a sleep lab and can cost over thousands of dollars. In contrast to this costly test, this sleep apnea test may prove to be just what the patient and doctors want to improve savings and detection.
“Right now we don’t have enough sleep clinics, sleep laboratories, and sleep specialists in the country to address all the sleep apnea that is out there,” says co-author Dr. Watson. “These initial results are impressive and suggest that ApneaApp has the potential to be a simple, noninvasive way for the average person to identify sleep apnea events at home and hopefully seek treatment.”
To determine if a person is experiencing sleep apnea signs, also called events, ApneaApp adapts an Android smartphone into a sonar system that can track minute changes in a person’s breathing patterns. Sonar works by using an echo. When an animal or machine makes a noise, it sends sound waves into the environment around it, and those waves bounce off nearby objects, reflecting back to the object that made the noise. The phone does the same, but emits inaudible sound waves that bounce off a sleeping person’s body, reflecting back to the phone’s microphone.
The sound waves are too low for adults to hear, so the app easily screens out background noise from people talking, cars, or other common sounds. The UW team developed new algorithms and signal-processing programs, both of which test the boundaries of what smartphones can do.
“Right now phones have sensing capabilities that we don’t fully appreciate,” says co-author Shyam Gollakota, assistant professor of computer science and engineering and director of the UW Networks and Mobile Systems lab. “If you can recalibrate the sensors that most phones already have, you can use them to achieve really amazing things.”
In the clinical study, 37 patients were tested using the sleep apnea test with the smart app at Harborview Medical Center. Researchers used a Samsung Galaxy S4 smartphone placed at the corner of the beds during their overnight sleep study. Nearly 300 hours of testing were done, and the app tracked various respiratory paterns including central apnea, obstructive apnea, and hypopnea with between 95% and 99% accuracy, compared to the use of polysomnography. This new app of course needs further testing at other research clinics, but once they are further tested, many of us look forward to testing this app for ourselves and passing on the savings to our patients.