Simple camera may help measure heart and respiration rates

A simple video camera paired with complex algorithms can help accurately monitor heart and respiration rates to track a person's health, scientists say.
The inexpensive method for monitoring the vital signs without touching a patient could have major implications for telemedicine, including enabling rapid detection of a heart attack or stroke occurring at home and helping avoid sudden infant death syndrome, researchers said.
"Heart and respiratory rates obviously tell us a lot about how an individual is doing," said Dr Joe Tsien, neuroscientist at the Medical College of Georgia at Georgia Regents University.
"Normally, caregivers have to put their hands on a patient to assess these rates. However our algorithms enable us to rapidly and accurately translate, for example, normally imperceptible movement of the skin in rhythm with our breathing into an accurate measure of respiration rate," Tsien said.

Scientists at MCG and China's BanNa Biomedical Research Institute are working to see if the approach can also accurately measure blood pressure.
To measure heart rate, the approach takes advantage of the fact that the blood vessels expand and contract with each heartbeat: more blood in the vessels means more camera light is absorbed rather than reflected.

Breathing causes a slight body movement that produces varying lengths of reflected light off the moving surface. In fact, Tsien noted, the two rates are closely tied and respiration rate can also be calculated based on heart rate, using his algorithms as well as other methods.

Within a few seconds, the algorithms enable light reflections to be sorted by source so that ambient signals from, say, a fluorescent lamp, can be ignored and distinct numbers can be calculated for heart and respiration rates.
False-positive rates were less than 3 per cent and false negatives under 1 per cent, indicating the device would be reliable even in rapidly changing scenarios such as a heart attack or stroke.
Measurements were taken multiple times on 15 human subjects, including seven males, eight females and one infant, who were a mix of Caucasians, Asians and blacks.
To assess accuracy, heart and respiratory rates were concurrently measured using standard approaches such as an electrocardiogram for the heart and airflow captured by a sensor under the nose while subjects were active and stationary.

To further assess accuracy, scientists also used the approach on still images such as photographs of humans, a Simpson cartoon character and the Mona Lisa painting. Their system correctly identified all as inanimate objects.
They also applied the technique to television footage of celebrities such as former US President Bill Clinton, and were able to detect varying heart and respiration rates in calm, happy and stressful situations.
The study was published in the journal PLOS ONE.