Washington, April 28 (IANS): A team of Indian-American researchers from the University of Washington (UW) has developed an app that uses a smartphone to wirelessly test for obstructive sleep apnoea in a person's bedroom.

Unlike other home sleep aponea tests in use, "ApneaApp" uses inaudible sound waves emanating from the phone's speakers to track breathing patterns without the need of special equipment or sensors attached to the body.

"ApneaApp" turns a smartphone into an active sonar system that can detect sleep apnoea events.

"It is similar to the way bats navigate. They send out sound signals that hit a target and when those signals bounce back, they know something is there," explained Rajalakshmi Nandakumar, lead author in the UW's department of computer science and engineering.

Tests in a home bedroom setting showed "ApneaApp" works efficiently at distances of up to three feet, in any sleeping position and even when the person is under a blanket.

The clinical study tested the app, that could be available to consumers in the next year or two, on 37 patients.

Researchers put a Samsung Galaxy S4 smartphone on a corner of the bed during the overnight sleep study.

During nearly 300 hours of testing, the app tracked various respiratory events including central apnoea, obstructive apnoea and hypopnea with between 95 and 99 percent accuracy, compared to intensive polysomnography.

"ApneaApp" correctly classified 32 out of 37 patients in the clinical study.

To determine, if a person is experiencing sleep apnoea events, "ApneaApp" transforms an Android smartphone phone into an active sonar system that tracks tiny changes in a person's breathing movements.

The phone's speaker sends out inaudible sound waves, which bounce off a sleeping person's body and are picked back up by the phone's microphone.

Because the sound waves are at a frequency adults cannot hear, the app easily screens out audible background noise from people talking, cars honking or a bedroom fan.

Right now phones have sensing capabilities that people do not fully appreciate.

"If you can recalibrate the sensors that most phones already have, you can use them to achieve really amazing things," added co-author Shyam Gollakota, assistant professor of computer science and engineering.

The 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, the authors noted.

The app is much simpler to use than other home sleep apnoea tests.

"Using ApneaApp at home over the course of several nights or weeks could produce a more complete picture of real-life sleeping patterns," the authors concluded.

The researchers are now exploring the process of getting the US Food and Drug Administration (FDA) approval.

The clinical study will be presented at the "MobiSys 2015" conference in Florence, Italy, in May this year.