Want to see another example of how mobile technology could make bigger, more expensive devices obsolete? Look no further than SpiroSmart, the app the turns your iPhone into a personal spirometer.

Anyone familiar with chromic lung ailments like asthma or cystic fibrosis are surely aware of what a spirometer does. For everyone else, a spirometer is a device that measures the volume of air inspired and expired by your lungs. Basically, it tells you how much and how fast you’re breathing out over the course of a few seconds. Traditional spirometers have users blow into a tube with a turbine, which helps to measure the flow speed.

Of course, the trick in turning a person’s smartphone into a spirometer is utilizing just the built-in microphone. Researchers at the University of Washington, UW Medicine and Seattle Children’s hospital say they’ve found a solution, and it’s quite impressive.

“The UW researchers found they could model a person’s trachea and vocal tract as a system of tubes to replace the spirometer, and use a phone to analyze the sound wave frequencies to detect when the breath is resonating in those natural pipes,” writes Hannah Hickey at the University of Washington.

“There are resonances that occur in the signal that tells you about how much flow is going through the trachea and the vocal tract, and that’s precisely the quantity that a clinician needs to know,” says lead researcher Shwetak Patel.

This is the first and only app of its kind, say the researchers. Other spirometer apps on the market aren’t accurate, as they rely on loudness of breath sounds to get a reading. Of course, this can be manipulated by how far away the user is holding their phone.

“There’s a big need in the pulmonary community to make testing cheaper and more convenient,” says Patel. “Other people have been working on attachments for the mobile phone that you can blow into. We said, ‘Let’s just try to figure out how to do it with the microphone that’s already there.’”

The team debuted their work at the Association for Computing Machinery’s International Conference on Ubiquitous Computing, and the results were good. Readings from SpiroSmart came within 5.1% of commercial portable spirometers already on the market, and many of those can cost thousands of dollars.

Preventative care via smart apps. That’s something patients and doctors can likely get behind.

[University of Washington via GeekWire]