Monitoring the vital signs of a patient is critical to managing their care, however, current approaches are limited in terms of sensing capabilities and sampling rates. The measurement process can also be uncomfortable due to the need for direct skin contact, which can disrupt the circadian rhythm and restrict the motion of the patient.  Now, a study from researchers at Cornell University demonstrates a non-invasive method for gathering blood pressure, heart rate, and breathing rate using a cheap system of radio-frequency signals and microchip tags, similar to the anti-theft tags department stores place on clothing and electronics.  The team states their tags measure mechanical motion by emitting radio waves that bounce off the body and internal organs, which, in turn, are then detected by an electronic reader gathering data from a location elsewhere in the room.  The opensource study is published in the journal Nature Electronics.

Previous studies show current approaches to monitoring vital signs are based on electrodes, optical absorption, pressure or strain gauges, stethoscope, and ultrasound or radio-frequency backscattering, all of which suffer particular drawbacks during application.  The current study shows the external and internal mechanical motion of a person can be directly modulated via radio-frequency signals integrated with unique wearable tags using near-field coherent sensing.

The current study develops near-field coherent sensing, a method to directly modulate the mechanical motion on the surface and inside a body onto radio signals integrated with a unique digital identification, allowing tags to measure internal bodily movement such as a heart as it beats or blood as it pulses under the skin. Results show while using near-field coherent sensing more electromagnetic energy is directed into the body tissue than with typical radio-frequency, meaning the signal from internal organs is amplified. Data findings shoe the shorter wavelength inside the body renders a small mechanical motion into a relatively large phase variation simultaneously, increasing the sensitivity.

The team states the tags are powered by electromagnetic energy supplied by a central reader, and because each tag has a unique identification code it transmits with its signal up to 200 people can be monitored simultaneously using just one central reader.  They go on to add the signal is as accurate as an electrocardiogram or a blood-pressure cuff and believe the technology could also be used to measure bowel movement, eye movement and many other internal mechanical motions produced by the body.

The team surmises they have developed a non-invasive system for monitoring vital signs inside the body based on radiowaves emitted by tags.  For the future, the researchers state for every garment in a person’s daily use, there could be a tag inegrated into them, with a cellphone reading and analyzing vital signs.

Source: Cornell University

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