A research team from the University of Washington has adapted a smartphone-based spirometry test to work with any kind of phone, including feature phones and landline phones, and to deliver clinically accurate results. 

Back in 2012, the University developed a smartphone app, SpiroSmart, that would use the measure lung function using the phone's microphone. But in attempting to put the device to work in low-resource settings, researchers discovered that smartphones were often unavailable, but cell phones in general were much more ubiquitious. Furthermore, since the only sensor SpiroSmart used was the microphone, the same service could be provided via a 1-800 number.

"We wanted to be able to measure lung function on any type of phone you might encounter around the world — smartphones, dumb phones, landlines, pay phones,” Shwetak Patel, a professor of computer science, engineering, and electrical engineering at UW told the University's Office of News and Information. “With SpiroCall, you can call a 1-800 number, blow into the phone and use the telephone network to test your lung function.”

The team will soon present a paper at a conference demonstrating that the accuracy of SpiroCall is within 6.8 percent of clinical grade spirometers. The acceptable margin for error in spirometry is 5 to 10 percent. This is even after accounting for the decrease in sound quality that occurs when the test has to be transmitted over a phone line or satellite connection. 

“We had to account for the fact that the sound quality you get over a phone line is worse,” Elliot Saba, a UW electrical engineering doctoral student, who co-wrote the paper told the university. “You can imagine how listening to someone play a song over a phone line would sound compared to listening to it on your music app — there’s a similar difference with a spirometry test.”

The team created an additional tool that helps train SpiroCall users to do the test correctly. It's a 3D-printed whistle that changes pitch when the user exhales. 

SpiroSmart -- the original app -- is currently undergoing the FDA clearance process. In preparing for clearance, researchers have collected data from more than 4,000 patients both in the United States and in India and Bangladesh, each time collecting both traditional spirometry data and data collected from the app. 

Correction: After we published our story, a few mobile spirometry startups whose products have hit the market reached out. We've updated the story to include them.

When Apple added spirometry to HealthKit in 2014, we noted that there were no smartphone connected spirometers on the market, but several companies working on that technology that were close to launching. That's no longer the case. Cohero Health, which also makes smartphone-connected inhalers, received FDA clearance for its smartphone-connected spirometer last summer. Additionally, Rome-based Medical International Research markets Smart One, a smartphone-connected peak flow meter.

MySpiroo, a Polish company, has developed a smartphone-connected peak flow meter that plugs into the phone's headphone jack. They have completed a prototype and plan to launch their second version soon. In addition, a Greek company called Respi, a member of DreamIt Health's latest accelerator class, is also building a smartphone spirometer. And Breathometer, the smartphone-connected breathalyzer device that has backing from Mark Cuban, could potentially move into spirometry too.