Continuous, noninvasive blood pressure monitoring has been a longtime goal of medicine because of blood pressure’s utility as a metric for clinicians.
However, options have been limited to internally placed arterial catheters or inflatable pressure cuffs, requiring frequent calibration with an inflatable cuff.
Ultrasound-based measurement
Raymond Jimenez and colleagues propose a new method based on "resonance sonomanometry," in which the artery is stimulated by an acoustic transducer (similar to a medical ultrasound scanner) and the resonant response and dimensions are measured using ultrasound.
Similar to how a guitar string changes pitch as its tension is manipulated, changing circumferential tension (by blood pulses) of the arterial wall changes its resonant frequency through the continuous phases of the cardiac cycle.
The method was tested on humans on the carotid artery in the neck and the axillary, brachial, and femoral arteries. Measurements were compared with those from a blood pressure cuff.
Not limited to an arm
All four sites produced measurements in a single subject that were broadly in line with those obtained from a cuff. Additional testing on the carotid arteries of six volunteers showed promising results, albeit with lower systolic values (predictable, given the carotid being closer to the heart than the brachial artery measured by the cuff).
According to the authors, their proposed device could be worn over any ultrasound-accessible artery, even including the radial (back of arm near hand), where the device could be worn like a watch.
Citation: Jimenez, R., Yurk, D., Dell, S., Rutledge, A. C., Fu, M. K., Dempsey, W. P., Rajagopal, A., & Brinley Rajagopal, A. (2024). Resonance sonomanometry for noninvasive, continuous monitoring of blood pressure. PNAS Nexus, 3(7). https://academic.oup.com/pnasnexus/article/3/7/pgae252/7717708 (open access)