Wearable ultrasound patch monitors deep blood pressure

Cardiovascular problems can now be easily detected earlier on and that too with greater precision through a new wearable ultrasound patch that non-invasively monitors blood pressure in arteries deep beneath the skin. The new ultrasound patch can continuously monitor central blood pressure in major arteries as deep as four centimeters (more than one inch) below the skin, reports scientists of San Diego in their work published in the journal Nature Biomedical Engineering.

"Wearable devices have so far been limited to sensing signals either on the surface of the skin or right beneath it. But this is like seeing just the tip of the iceberg," said Sheng Xu, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering and the corresponding author of the study. "By integrating ultrasound technology into wearables, we can start to capture a whole lot of other signals, biological events, and activities going on way below the surface in a non-invasive manner."

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According to the researchers, applications include real-time, continuous monitoring of blood pressure changes in patients with heart or lung disease, as well as patients who are critically ill or undergoing surgery. The patch uses ultrasound, so it could potentially be used to non-invasively track other vital signs and physiological signals from places deep inside the body.

"This has the potential to be a great addition to cardiovascular medicine," said Dr. Brady Huang, a co-author on the paper and radiologist at UC San Diego Health. "In the operating room, especially in complex cardiopulmonary procedures, accurate real-time assessment of central blood pressure is needed--this is where this device has the potential to supplant traditional methods."

Credit: Chonghe Wang/Nature Biomedical Engineering

Routine check-up does not measure central blood pressure. However, the device measures central blood pressure--which differs from the blood pressure that's measured with an inflatable cuff strapped around the upper arm, known as peripheral blood pressure. Central blood pressure is the pressure in the central blood vessels, which send blood directly from the heart to other major organs throughout the body. Clinicians consider central blood pressure more accurately than peripheral blood pressure and also say it's better at predicting heart disease.

The state-of-the-art clinical method is invasive, involving a catheter inserted into a blood vessel in a patient's arm, groin or neck and guiding it to the heart.

The patch was tested on a male subject, who wore it on the forearm, wrist, neck, and foot. Tests were performed both while the subject was stationary and during exercise. Recordings collected with the patch were more consistent and precise than recordings from a commercial tonometer. The patch recordings were also comparable to those collected with a traditional ultrasound probe.

According to the researchers, the major advancement in their work is the transformation of ultrasound technology into a wearable platform which will help the clinicians to perform continuous non-invasive monitoring of major blood vessels deep underneath the skin, not just in shallow tissues.