Wearable Ultrasound Patch Monitors Blood Pressure

Posted on November 1st, 2018 by Dr. Francis Collins

Caption: Worn on the neck, the device records central blood pressure in the carotid artery (CA), internal jugular vein (Int JV) and external jugular vein (Ext JV).
Credit: Adapted from Wang et al, Nature Biomedical Engineering

There’s lots of excitement out there about wearable devices quietly keeping tabs on our health—morning, noon, and night. Most wearables monitor biological signals detectable right at the surface of the skin. But, the sensing capabilities of the “skin” patch featured here go far deeper than that.

As described recently in Nature Biomedical Engineering, when this small patch is worn on the neck, it measures blood pressure way down in the central arteries and veins more than an inch beneath the skin [1]. The patch works by emitting continuous ultrasound waves that monitor subtle, real-time changes in the shape and size of pulsing blood vessels, which indicate rises or drops in pressure.

We’ve all had an inflatable cuff wrapped around an arm to measure our peripheral blood pressure. But the more accurate predictor of a developing heart problem is the central blood pressure. That’s the flow of blood through the aorta, the main artery that carries blood to the rest of the body.

The problem is getting a gold standard read on central blood pressure requires inserting a catheter into a blood vessel and guiding it with great precision to the aorta. That’s not practical. While non-invasive, handheld devices have been developed for measuring central blood pressure in more distal major blood vessels, such as the carotid artery in the neck, it’s been tough to get accurate readings.

That’s why a team of researchers, led by Sheng Xu and graduate student Chonghe Wang, University of California San Diego, La Jolla, decided to merge ultrasound technology with wearables. Their prototype wearable ultrasound patch consists of a thin sheet of silicone polymer with elastic qualities. The sheet is patterned with a visible array of small electronic parts connected by lightweight, spring-shaped copper wires that can stretch, bend, and twist without breaking.

Then there is the customized software. It allows continuous monitoring of central blood pressure based on the ultrasound readout. Each peak and valley reading in the blood pressure real-time measurement, called a waveform, represents the heart’s normal activity. Any hiccup in the blood pressure waveform can be used to indicate a problem, such as an irregular heartbeat or impending heart failure.

The patch has already been tested while worn on the wrist, forearm, neck, and foot. The researchers also tried it out during exercise and rest. So far, the new device appears to function better than any commercially available, non-invasive device for measuring central blood pressure.

For the current patch to monitor central blood pressure, it must be hooked up to external wires. But the researchers envision a future wireless version, in which a power source and data processing units are fully integrated into the patch. The hope is that one day soon their device will offer round-the-clock monitoring of central blood pressure. That could utterly transform our management of hypertension.

References:

[1] Monitoring of the central blood pressure waveform via a conformal ultrasonic device . Wang C, Li X, Hu H, Zhang, L, Huang Z, Lin M, Zhang Z, Yun Z, Huang B, Gong H, Bhaskaran S, Gu Y, Makihata M, Guo Y, Lei Y, Chen Y, Wang C, Li Y, Zhang T, Chen Z, Pisano AP, Zhang L, Zhou Q, Xu S. Nature Biomedical Engineering. September 2018, 687-695.

Links:

Sensors (National Institute of Biomedical Imaging and Bioengineering/NIH)

Ultrasound (NIBIB)

High Blood Pressure (National Heart, Lung, and Blood Institute/NIH)

Sheng Xu Lab (University of California San Diego, La Jolla)

NIH Support: National Institute of Biomedical Imaging and Bioengineering