A smartphone app that measures the user's heart rate is not only a popular feature with consumers, but it sparked an idea for a Worcester Polytechnic Institute researcher who now is turning such phones, and eventually tablet devices, into medical monitors able to capture and transmit vital physiological data.

A team led by Ki Chon, professor and head of biomedical engineering at the institute, located in Worcester, Mass., has developed a smartphone application that can measure not only heart rate, but also heart rhythm, respiration rate, and blood oxygen saturation using the phone's built-in video camera.

The developers claim the new app yields vital signs as accurate as standard medical monitors now in clinical use.

"This gives a patient the ability to carry an accurate physiological monitor anywhere, without additional hardware beyond what's already included in many consumer mobile phones," Chon's team writes. "One of the advantages of mobile phone monitoring is that it allows patients to make baseline measurements at any time."

The application analyzes video clips recorded while the patient's fingertip is pressed against the lens of the phone's camera. As the camera's light penetrates the skin, it reflects off of pulsing blood in the finger. The application is able to correlate subtle shifts in the color of the reflected light with changes in the patient's vital signs.

Chon, who is an expert on signal processing, previously has developed algorithms that monitor a range of vital signs using traditional clinical devices such as a Holter heart monitor. In the new study, Chon and his team created and adapted algorithms to process the data gathered by the phone's video camera.

To test for accuracy, volunteers at WPI donned the standard monitoring devices now in clinical use for measuring respiration, pulse rate, heart rhythm, and blood oxygen content. Simultaneously, the volunteers pressed a finger onto the camera of a Motorola Droid phone. While all devices were recording, the volunteers went through a series of breathing exercises while their vital signs were captured.

Analysis of the data showed that Chon's new smartphone monitor was as accurate as the traditional devices, the researchers say. While this study was done on a Droid, Chon says the technology is adaptable to most smart phones.

Furthermore, since the new technology can measure heart rhythm, Chon believes the smart-phone app could be used to detect atrial fibrillation (AF), which is the most common form of cardiac arrhythmia.

"We are building that application now, and we have started a preliminary clinical study with colleagues at UMass Medical School to use the smart phone to detect AF," Chon says.