Asthma? There’s an app for that. Currently, those who suffer from asthma or other chronic lung problems only get a measure of their lung function at the doctor’s office a few times a year by blowing into a specialized piece of equipment – the spirometer. But, more frequent testing at home could detect problems earlier, say researchers at the University of Washington, Seattle, who have created a new app, called the SpiroSmart, that lets people monitor their lung function by simply by blowing into their smartphones.

“There’s a big need in the pulmonary community to make testing cheaper and more convenient,” said Shwetak Patel, the lead researcher and an assistant professor of computer science and engineering and electrical engineering. “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.’”

Existing spirometers have pulmonary patients blow into a tube with a small turbine that measures how much and how fast the person can breathe out, which tells doctors whether their airways are narrowed or filled with mucous. The 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.

People would use the SpiroSmart app by holding a smartphone at arm’s length and following the prompts to breathe in deeply and then exhale as hard and fast as they can. The scientists found in their study of 52 volunteers that the app came within 5.1 percent of a commercial portable spirometer that costs thousands of dollars.