Portable microwave sensors for measuring vital signs

Washington, D.C. (November 9, 2010) — Current medical techniques for monitoring the heart rate and other vital signs use electrodes attached to the body, which are impractical for patients who want to move around. Plasma physicist Atsushi Mase, a scientist at Kyushu University in Japan, and colleague Daisuke Nagae have developed a new technique to disconnect people from their electrodes by using microwaves.

The work, which could lead to the development of non-invasive, real-time stress sensing in a variety of environments, is described in a recent issue of the journal Review of Scientific Instruments, which is published by the American Institute of Physics.

The system uses very weak microwaves to irradiate — and scatter off — the human body. A sensitive microwave sensor monitors the reflected waves, which change in phase in response to motions of the body, including the regular displacement of the chest during breathing or, the slight movement of the chest caused by the beating heart.

“The skin surface moves slightly,” Mase says, “synchronizing to respiration and heart beat.”

Using signal processing algorithms and techniques to filter out the effects of random body motions, Mase and Nagae were able to detect changes in heart rate in near real-time, which allows an evaluation of autonomic nervous system activity.

“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 says. In the future, the system could even be used as a security monitor to distinguish the subtle signs of stress in potential terrorists.

The article, “Measurement of heart rate variability and stress evaluation by using microwave reflectometric vital signal sensing” by Daisuke Nagae and Atsushi Mase appears in the journal Review of Scientific Instruments. See:

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Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques. Its contents include original and review articles on instruments in physics, chemistry, and the life sciences; and sections on new instruments and new materials. One volume is published annually. Conference proceedings are occasionally published and supplied in addition to the Journal’s scheduled monthly issues. RSI publishes information on instruments, apparatus, techniques of experimental measurement, and related mathematical analysis. Since the use of instruments is not confined to the physical sciences, the journal welcomes contributions from any of the physical and biological sciences and from related cross-disciplinary areas of science and technology. See: http://rsi.aip.org/


The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world’s largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.

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