At least 115 people die every day in the U.S. after overdosing on opioids, according to the National Institute on Drug Abuse.

And in 2016, illegal injectable opioids became the most common drug involved in overdose-related deaths. This spike has led to a national public health crisis and epidemic.

During an overdose, a person breathes slower or stops breathing altogether. These symptoms are reversible with the drug naloxone if caught in time.

But people who use opioids by themselves have no way of asking for help in the event of an overdose.

Researchers at the University of Washington have developed a cellphone app, called Second Chance, that uses sonar to monitor someone’s breathing rate and sense when an opioid overdose has occurred. The app accurately detects overdose-related symptoms about 90 percent of the time and can track someone’s breathing from up to 3 feet away. The team will publish its results Jan. 9 in Science Translational Medicine.