Taking your blood pressure may become as easy as taking a video selfie if a new smartphone app proves itself.
High blood pressure can be a warning sign of a heart attack or stroke, but half of those with hypertension don't know it. Developing an easy at-home blood pressure screen could potentially save lives.
A new technology called transdermal optical imaging gives a picture of the blood flow in your face, which reveals your blood pressure, researchers say.
"We found, using a smartphone, we can accurately measure blood pressure within 30 seconds," said lead researcher Kang Lee.
Lee is research chair of developmental neuroscience at the University of Toronto.
"We want to use this technology to help us to make people aware of their blood pressure and monitor it," he said.
Lee doesn't intend this technology to replace standard "cuff" blood pressure measuring, but rather to make blood pressure easy to take at home.
So how does it work?
The technology uses light to penetrate the skin and optical sensors in smartphones to create an image of blood flow patterns. These patterns are then used to predict blood pressure, Lee explained.
"Once you know how blood concentration changes in different parts of your face, then we can learn a lot of things about your physiology, such as your heart rate, your stress and your blood pressure," he said.
Lee discovered the relationship between facial blood flow and blood pressure by accident. He was using transdermal optical imaging to try to develop a way of telling when kids were lying by correlating blood flow to areas of the face with fibbing.
To test the technology's blood pressure predictions, Lee and his colleagues tried it out on more than 1 300 Canadian and Chinese adults with normal blood pressure. Each participant had a two-minute video recorded using an iPhone with transdermal optical imaging software.
Lee's team compared the results of the videos with blood pressure readings taken the standard way.
They found that the video prediction of systolic blood pressure (the upper number) was almost 95% accurate. The prediction of diastolic pressure (the bottom number) was nearly 96% accurate.
The report was published August 6 in the journal Circulation: Cardiovascular Imaging.
But several problems need to be solved before this technique is ready for primetime, Lee said. For one, the recordings made in the study were in highly controlled environments.
The researchers hope to make the system work with normal home lighting and to shorten the time needed for the recording to 30 seconds.
They also need to test the technology on people with high and low blood pressure and a variety of skin tones.
"Smartphones are really smart," Lee said. "We cannot only use it for social networking, it can actually help you become aware of your physiological state."
But one specialist is sceptical that this system could ever be widely used.
"It would be cool to just look at your phone and then you know your blood pressure," said Ramakrishna Mukkamala, a professor of electrical and computer engineering at Michigan State University.
Mukkamala said, however, that it's doubtful that facial video can yield specific information about blood pressure.
"There's no physics theory behind it," said Mukkamala, a cardiovascular researcher who wrote an accompanying editorial.
If it were to work, "a lot of technical challenges have to be overcome", he said. "These include different skin shades, different room temperatures and different lighting. Also, different angles of the face. And those aren't easy problems."