In the not-so-distant future, patients having their heart rate or other vital signs monitored may not have to be wired up with electrodes. Scientists Atsushi Mase and Daisuke Nagae, at Kyushu University in Japan, have developed a method of remotely measuring such data using microwaves. This means that people would be free to move around as they were being monitored, or in some applications, would not even know that it was happening.

The Kyushu system works by irradiating the patient’s body with very weak microwaves. A microwave sensor detects the waves as they reflect back. The phase of the reflected waves will change in response to motions in the body, such as the subtle rising and falling of the chest as caused by breathing or a beating heart. Signal processing algorithms are incorporated to filter out other random body movements.

Mase and Nagae have successfully used their system to detect changes in a test subject’s heart rate in near real-time. “We plan to apply the system to various conditions, including for clinical use – such as for the overnight monitoring of human vital signs – and as a daily health monitor, including detecting signs of sleepiness in drivers and preventing stress-related illnesses," he said.

It has also been suggested that the technology could be used in airport security, to detect the subtle signs of stress exhibited by potential terrorists.

The research was recently published in the journal Review of Scientific Instruments.