New non-invasive ‘tag’ system measures vital signs with radio waves.

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 breath 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 state that their tags measure mechanical motion by emitting radio waves that bounce off the body and internal organs, which are then detected by an electronic reader that gathers the data from a location elsewhere in the room.  The opensource study is published in the journal Nature Electronics.

Previous studies show that current approaches to monitoring vital signs are based on body electrodes, optical absorption, pressure or strain gauges, stethoscope and ultrasound or radio-frequency backscattering, each of which suffers particular drawbacks during application.  The current study shows that 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 body movement such as a heart as it beats or blood as it pulses under skin. Results show that in near-field coherent sensing more electromagnetic energy is directed into the body tissue than with typical radio-frequency so the signal from internal organs is amplified. Data findings show that at the same time, the shorter wavelength inside the body renders a small mechanical motion into a relatively large phase variation, which also increases the sensitivity.

The team state that 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 that the signal is as accurate as an electrocardiogram or a blood-pressure cuff and believe that the technology could also be used to measure bowel movement, eye movement and many other internal mechanical motions produced by the body.

The team surmise that they have developed a non-invasive system for monitoring vital signs which modulates the detailed motion on and inside the body via radiofrequency signals via tags.  For the future, the researchers state that for every garment in a person’s daily use, there could be a tag on them, with a cellphone reading and analysing vital signs.

Source: Cornell University


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