New app turns smartphone into health monitor

Researchers have developed a new smartphone app that monitors how heart and lung patients walk and can alert doctors when their symptoms worsen.
GaitTrack, an app developed by researchers at the University of Illinois at Urbana-Champaign and the U of I at Chicago, turns a smartphone into a sophisticated medical device.
Unlike other apps that merely count steps, GaitTrack uses eight motion parameters to perform a detailed analysis of a person's gait, or walking pattern, which can tell physicians much about a patient's cardiopulmonary, muscular and neurological health.
"Fitness apps and devices are tuned for healthy people," said Bruce Schatz, the head of medical information science and a professor of computer science at the U of I.

"They cannot accurately measure patients with chronic disease, who are the biggest medical market. A pedometer is not a medical device. But a cheap phone with GaitTrack software is," Schatz said.
According to Schatz, gait is sometimes called the "sixth vital sign" - after temperature, blood pressure, heart rate, respiratory rate and blood oxygen level.

Gait speed involves several systems of the body working together in coordination, so changes in gait can be a sign of trouble in one or more systems.
Doctors often use an assessment called the six-minute walk test for patients with heart and lung disease, such as congestive heart failure, chronic obstructive pulmonary disease (COPD) and asthma.

Patients with chronic disease often cannot be measured with typical pedometers since they tend to walk with shorter, more careful strides, or to shuffle, so specialised medical accelerometers are used.
The Illinois team used GaitTrack to administer six-minute walk tests to 30 patients with chronic lung disease and found that it monitored more accurately - and more cheaply - than the medical accelerometers.
In addition, they discovered that analysis of the gait data could predict lung function with 90 per cent accuracy, within an age group.
Schatz envisions the GaitTrack app running constantly in the background as a patient carries a phone.

The phone would periodically collect data, analyse it and keep tabs on the patient's status, alerting the patient or patient's doctor when it detects changes in gait that would indicate a decline in health so that treatment could be adjusted responsively.
The team published its findings in the journal Telemedicine and e-Health.