Monitoring a person’s vital signs (heart rate, blood pressure, respiratory rates, and breath effort) is crucial to managing their health. The current methods of practice in the measurement process can be uncomfortable because of their necessity for direct skin contact. Moreover, they can disrupt the circadian rhythm and restrict the motion of a person. These approaches are also limited in terms of sensing capabilities and sampling rates. They are based on very old technology.
The sphygmomanometer was invented by Samuel Siegfried Karl Ritter von Basch in 1881. Devices based on its basic pressure principle are still in use. (credit: Wellcome Trustees)
Fortunately, there is soon to be a better way: with the use of proximity tags that emit radio waves a person’s heart, lungs, and blood pressure could be monitored. The signal is as accurate as any electrocardiogram or a blood-pressure cuff.
A wireless health-care system. “Hui and Kan report a system for monitoring a person’s vital signs, such as their heart rate. The system is wireless and does not require skin contact. It uses a device known as a passive radio-frequency identification tag, which can be integrated into clothing. The tag comprises an embroidered antenna and sensors and is powered by electromagnetic energy (blue arrow) from an electronic device called a reader. The antenna transmits radio waves that enter the body and are reflected. The backscattered signal is then picked up by the on-tag sensors. Finally, this information is sent to the reader (red arrow) to allow data on the person’s vital signs to be retrieved.”
Cornell University engineers have developed a concept termed “near-field coherent sensing” (NCS). It is a method to directly attune the mechanical motion on the surface and inside a body (such as breathing, heartbeat, pulse, etc.) onto multiplexed radio signals that are integrated with a unique digital identification (ID). Passive (no batteries required) RFID tags, that are powered remotely by electromagnetic energy supplied from a central reader, are what measure the person’s internal body motion(s) by emitting radio waves.
These cracker-size microchip “tags” are similar to the anti-theft tags placed on clothing and electronics in department stores. The radio waves they emit bounce off the body and its internal organs to then be detected by an electronic reader located elsewhere that gathers the data. According to Edwin Kan, professor of electrical and computer engineering, the system works like a radar.
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. The transmission facilitates simultaneous sensing for multiple points and multiple persons. Kan explains, “If this is an emergency room, everybody that comes in can wear these tags or can simply put tags in their front pockets, and everybody’s vital signs can be monitored at the same time. I’ll know exactly which person each of the vital signs belongs to.”
Kan and his graduate student Xiaonan Hui are also in collaboration with professor Jintu Fan and associate professor Huiju Park from Cornell’s Department of Fiber Science and Apparel Design, who have demonstrated a way to embroider the tags directly onto clothing using fibers coated with nanoparticles. This affiliation has left Hui envisioning a future where people can monitor their health, in real-time and with little or no effort required, just by wearing their clothes. “For every garment in our daily use, there could be a tag on them, and your cellphone will read your vital signs and will tell you some kind of information about your condition that day,” said Hui.
NCS opens up new doors of opportunity for vital sign monitoring with accuracy, comfort, convenience and at a low-cost. The technology could eventually be used to even measure bowel movement, eye movement and many other internal mechanical motions produced by the body. The team plans to do more extensive testing with Dr. Ana Krieger, medical director of the Center for Sleep Medicine and associate professor of clinical medicine, of medicine in clinical neurology and of clinical genetic medicine at Weill Cornell Medicine. The system, as of now, is detailed in the paper called “Monitoring Vital Signs Over Multiplexed Radio by Near-Field Coherent Sensing,” which has been published in the journal Nature Electronics.
Edwin Kan, professor of electrical and computer engineering at Cornell, holds a radio frequency identification tag.