According to a study published in Nature Biomedical Engineering on November 20, 2024, a team of researchers at the University of California San Diego created an enhanced wearable ultrasound patch that provides ongoing and noninvasive blood pressure monitoring.
This small, stretchy skin patch uses ultrasound to continuously monitor blood pressure deep inside the body. A comprehensive clinical validation on 117 subjects, including patients in the intensive care unit, has demonstrated its potential as a simpler and more reliable alternative to current clinical methods for monitoring blood pressure. Image Credit: David Baillot/UC San Diego Jacobs School of Engineering
Their study is significant since the gadget is the first wearable ultrasonic blood pressure monitor to be rigorously and comprehensively validated on over 100 individuals.
The technique can potentially increase the quality of cardiovascular health monitoring in clinics and homes.
Traditional blood pressure measurements with a cuff, which are limited to providing one-time blood pressure values, can miss critical patterns. Our wearable patch offers a continuous stream of blood pressure waveform data, allowing it to reveal detailed trends in blood pressure fluctuations.
Sai Zhou, Study Co-First Author and PhD Candidate, Jacobs School of Engineering, University of California San Diego
The patch is a soft and elastic device roughly the size of a postage stamp applied to the skin. When worn on the forearm, it provides accurate, real-time blood pressure readings from deep within the body. The patch is made of silicone elastomer and contains an array of tiny piezoelectric transducers sandwiched between flexible copper electrodes. The transducers send and receive ultrasound waves that measure changes in the diameter of blood vessels and transform them into blood pressure readings.
Technological Improvements to Wearable Ultrasound
The wearable ultrasound patch is based on an earlier prototype developed by Sheng Xu, a professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at UC San Diego. Researchers redesigned the patch with two significant changes to increase its efficacy for continuous blood pressure monitoring.
First, they packed the piezoelectric transducers closer together, allowing them to provide more coverage and better target smaller arteries like the brachial and radial arteries, which are more therapeutically significant. Second, they added a backing layer to decrease redundant transducer vibrations, which enhanced signal clarity and arterial wall tracking accuracy.
In tests, the device provided findings similar to those of a blood pressure cuff, and another clinical device known as an arterial line, a sensor put into an artery to continually monitor blood pressure. The arterial line is the gold standard for measuring blood pressure in intensive care units and operating rooms, but it is very intrusive, restricts patient mobility, and can cause pain or discomfort.
The patch is a simpler and more reliable option, as demonstrated in validation testing on patients undergoing arterial line operations in cardiac catheterization laboratories and intensive care units.
Comprehensive Clinical Validation
Researchers did comprehensive testing to ensure the patch’s safety and accuracy. A total of 117 people participated in experiments that measured blood pressure in various activities and environments. In one series of experiments, seven people wore the patch while cycling, lifting an arm or leg, doing mental arithmetic, meditating, eating meals, and drinking energy drinks.
In a wider cohort of 85 patients, the patch was tested during posture changes from sitting to standing. In all experiments, the patch produced results that were quite similar to those of blood pressure cuffs.
The patch's ability to continuously track blood pressure was tested in 21 patients in a cardiac catheterization lab and four in the intensive care unit following surgery. Measurements from the patch nearly matched those from the arterial line, demonstrating its promise as a noninvasive alternative.
A big advance of this work is how thoroughly we validated this technology, thanks to the work of our medical collaborators. Blood pressure can be all over the place depending on factors like white coat syndrome, masked hypertension, daily activities or use of medication, which makes it tricky to get an accurate diagnosis or manage treatment. That’s why it was so important for us to test this device in a wide variety of real-world and clinical settings. Many studies on wearable devices skip these steps during development, but we made sure to cover it all.
Sheng Xu, Professor, Aiiso Yufeng Li Family Department of Chemical and Nano Engineering, University of California San Diego
Next Steps
The research team plans for large-scale clinical trials and intends to use machine learning to enhance the device’s capabilities. Efforts are being made to validate a wireless, battery-powered version for long-term use and seamless connection with current hospital systems.
Sai Zhou, Geonho Park, Katherine Longardner, Muyang Lin, Baiyan Qi, Xinyi Yang, Xiaoxiang Gao, Hao Huang, Xiangjun Chen, Yizhou Bian, Hongjie Hu, Ray S. Wu, Wentong Yue, Mohan Li, Chengchangfeng Lu, Ruotao Wang, Siyu Qin, Isac Thomas, Benjamin Smarr, Erik B. Kistler, Belal Al Khiami, Irene Litvan and Sheng Xu, UC San Diego; and Esra Tasali and Theodore Karrison, The University of Chicago are the study co-authors.
Wellcome Trust Innovator Award (WT215841/Z/19/Z) and the National Institutes of Health (1 R01 EB3346401) supported the study.