Alaina Brinley Rajagopal, a visiting associate in electrical engineering, an emergency medicine physician, and a co-author of the new paper describing the new technique, demonstrates the current prototype of the resonance sonomanometry blood pressure device (Photo – Daniel Cellucci)
A multidisciplinary team of Caltech researchers has figured out how to measure blood pressure anywhere on the body with next to no disruption to the patient. A device using sound waves promises to monitor blood pressure at home, in hospitals, and possibly even in remote locations.
By Kimm Fesenmaier, Caltech
The new patented technique, called resonance sonomanometry, uses sound waves to gently stimulate resonance in an artery and then uses ultrasound imaging to measure the artery’s resonance frequency, arriving at a true measurement of blood pressure. In a small clinical study, the device, which gives patients a gentle buzzing sensation on the skin, produced results akin to those obtained using the standard-of-care blood pressure cuff.
“We ended up with a device that is able to measure the absolute blood pressure—not only the systolic and diastolic numbers that we are used to getting from blood pressure cuffs—but the full waveform,” says Yaser Abu-Mostafa (PhD ’83), professor of electrical engineering and computer science. “With this device you can measure blood pressure continuously and in different sites on the body, giving you much more information about the blood pressure of a person.”
“This team has been working for almost a decade, trying to build something that makes a difference, that is good enough to solve a real clinical problem,” says Aditya Rajagopal (BS ’08, PhD ’14), visiting associate in electrical engineering at Caltech, research adjunct assistant professor of biomedical engineering at USC, and a co-author of the new paper. The resulting Esperto device is small, noninvasive, relatively inexpensive, and it has an automated method for locating the patient’s blood vessel without needing to be physically repositioned.
Blood pressure 101
Blood pressure is simply the force of blood pushing on the walls of the body’s blood vessels as it gets pumped around the body. High blood pressure, or hypertension, is related to risk of heart attack, stroke, chronic kidney disease, and other health problems. Low blood pressure, or hypotension, can also be a serious problem because it means the blood is not carrying enough oxygen to the organs. Taking regular measurements of blood pressure is considered one of the best ways to monitor overall health and to identify potential problems.
Most of us have experienced the cuff-style measurement of blood pressure. A nurse, doctor, or machine inflates a cuff that fits around the upper arm until blood can no longer flow, and then slowly releases the air from the cuff while listening for the sound that blood makes as it once again begins to flow. The pressure in the cuff at that point corresponds to the blood pressure in the patient’s arteries. But this technique has limitations: It can only be performed periodically, as it involves occluding a blood vessel, and can only collect data from the arm.
The team says the device solves longstanding blood pressure monitoring problem. And Rajagopal says it is the product of a million small leaps. “Everything we’ve done is a product of the exact mistakes we’ve made over time,” he says, “and all the work that others have done too.”
“This work is emblematic of what makes Caltech so remarkable: solving a very hard problem by going back to first principles and understanding a physical phenomenon at the fundamental level,” says Fred Farina, Caltech’s Chief Innovation and Corporate Partnerships Officer. “This approach, combined with the tenacity and entrepreneurial drive of the team, is our homemade recipe for societal impact and improving people’s lives.”
The paper describing the new technique is titled “Resonance sonomanometry for noninvasive, continuous monitoring of blood pressure.” Its authors are Yaser Abu-Mostafa (PhD ’83) and Aditya Rajagopal (BS ’08, PhD ’14). Additional authors on the paper include Raymond Jimenez (BS ’13), Steven Dell, Austin C. Rutledge, Matt K. Fu (BS ’13), William P. Dempsey (PhD ’12) of Esperto Medical, and Dominic Yurk (BS ’17, PhD ’23). The work at Caltech was supported by Caltech trustee Charles Trimble (BS ’63, MS ’64), the Carver Mead Innovation Fund, and the Grubstake Fund.
This article was edited for brevity and clarity. Read the full article at this link.
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