Credit: UCSD 

A team at the University of California San Diego has created an advanced wearable ultrasound patch designed for continuous, non-invasive blood pressure monitoring. This innovative patch is the first of its kind to undergo extensive clinical validation involving over 100 patients. The researchers believe this device could significantly enhance cardiovascular health monitoring both in clinical settings and at home. Their findings were published in Nature Biomedical Engineering.

Traditional blood pressure measurement methods, such as cuffs, provide only single-time readings and can miss critical blood pressure patterns. The new wearable patch, however, offers a continuous stream of blood pressure waveform data, revealing detailed trends in blood pressure fluctuations. According to Sai Zhou, a co-first author of the study and recent Ph.D. graduate from the UC San Diego Jacobs School of Engineering, this continuous monitoring capability is a significant advancement.

The patch is a soft, stretchy device, about the size of a postage stamp, that adheres to the skin on the forearm. It provides precise, real-time, continuous non-invasive blood pressure readings from deep within the body. The device features a silicone elastomer housing an array of small piezoelectric transducers between stretchable copper electrodes. These transducers transmit and receive ultrasound waves to track changes in blood vessel diameter, converting these changes into blood pressure values.

Building on an earlier prototype from Sheng Xu's lab, the researchers made two key improvements to the patch. They packed the piezoelectric transducers closer together for wider coverage of smaller arteries, such as the brachial and radial arteries. Additionally, they added a backing layer to dampen redundant vibrations from the transducers, improving signal clarity and tracking accuracy.

Testing of the patch showed results comparable to those from a traditional blood pressure cuff and an arterial line sensor, which is the gold standard in intensive care units and operating rooms. The patch was validated in a study involving 117 subjects, including tests during daily activities and posture changes. Results closely matched those from blood pressure cuffs in all tests.

Further validation was conducted in 21 patients in a cardiac catheterization lab and four patients in the ICU after surgery, with measurements aligning with arterial line results. The research team plans to prepare for large-scale clinical trials and aims to integrate machine learning to enhance the device's capabilities. They are also working on a wireless, battery-powered version for long-term use and integration with existing hospital systems.

Sheng Xu emphasized the importance of thorough validation in various real-world and clinical settings, noting that many studies on wearable devices skip these critical steps. The team's comprehensive approach ensures the reliability and accuracy of their new technology.

Paper | Nature Biomedical Engineering