SpiroCall, a technology that can accurately measure lung function over a phone, has been developed by researchers from the University of Washington.

The computer science and engineering and electrical engineering researchers created a system that uses the microphone built into any smartphone, land line or payphone in the world, to transmit the audio to a call-in center.

The team combined algorithms to provide lung function estimates despite possible low-quality audio. The algorithm expects one second of silence before the start of the test to gauge the ambient noise level of the room, and if the noise level is above a certain level, the patient is asked to find a more quiet setting or perform the test at a later time.
“The algorithm uses the phone’s microphone as an uncalibrated pressure sensor and converts the audio captured by the microphone into an estimate of the flow rate of air exiting from the patient’s mouth,” Mayank Goel, lead author and University of Washington computer science and engineering doctoral student, told HCB News.

SpiroCall’s results came within 6.2 percent of results from clinical spirometers used in hospitals and doctor’s offices. This is between the industry’s standard of five to 10 percent, since there is variability in the way a patient exhales during each spirometry test.

In 2012, SpiroSmart for smartphone use was introduced, which allows patients to monitor their lung function by breathing and exhaling as fast and hard as possible until they can’t exhale anymore. The phone’s microphone senses sound and pressure from the patient’s breath and then sends the information to a central server.

Within the last four years, the researchers collected data from more than 4,000 patients who visited clinics in Seattle and Tacoma, and India and Bangladesh, who had their lung function measured both by SpiroSmart and a traditional spirometer.

After a survey from the patients in India and Bangladesh, the team found that many of the patients did not have smartphones so they would not be able to use the technology from home. As a result, SpiroCall was created.

“[SpiroCall is not] dependent on smartphones to provide medical-grade health sensing to the users,” said Goel. “This can have huge implications in the developing world where more than 80 percent of the phone users still do not use a smartphone.”

A 3-D printed whistle was also created that changes pitch when the patient exhales and can be used with SpiroCall to improve the test performance for patients whose vocal cords cannot produce enough sound for the microphone to pick up.

The team plans on collecting additional data and figuring out how to best communicate test results to patients. “We have explored dictating the results back on the phone call itself using text-to-speech or sending them a text message at the end of the call,” said Goel, but he believes the bigger challenge is finding a good way to train patients in doing the test properly.

“While everyone, including us, is trying to enable so many useful capabilities on smartphones, we should not forget that if something has direct and immediate implications, it is important to see if we can enable similar technology on non-smartphones as well,” he said.

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