Researchers have developed a lightweight wearable patch that is able to accurately monitor blood pressure round the clock.
Standard blood pressure checks with an inflatable cuff only take one-off measurements, and averaging multiple measurements can be inaccurate and miss vital patterns.
The current gold standard when it comes to constant blood pressure monitoring is the use of an arterial line, which is a thin catheter inserted into an artery.
While accurate, it is highly invasive, can cause discomfort and pain, and limits mobility.
It is generally suited only to clinical settings, whereas a wearable patch could potentially be used anywhere, including round-the-clock monitoring at home.
Study co-author Sai Zhou of the University of California San Diego said that the ultrasound patch provides “a continuous stream of blood pressure waveform data”, allowing it to reveal “detailed trends in blood pressure fluctuations”.
The patch itself is described as the size of a postage stamp and is made of a flexible silicone elastomer that adheres to the skin.
Inside the device, piezoelectric transducers are sandwiched between stretchable copper electrodes.
Ultrasound tracks changes in the diameter of blood vessels
These transducers receive and transmit ultrasound waves that track changes in the diameter of blood vessels, which can be deep within the body.
The ultrasound data is then converted into standard blood pressure measurements.
The current device improves on earlier prototypes by packing the piezoelectric transducers closer together, allowing wider coverage to better target smaller but clinically significant arteries, such as the brachial and radial arteries.
The researchers also added a backing layer to dampen redundant vibrations from the transducers, to improve signal clarity and overall accuracy.
In tests, results from the device were said to be comparable to blood pressure cuffs and arterial lines.
A total of 117 volunteers took part in the trials, which involved monitoring blood pressure in a variety of settings and activities.
These included patients in a cardiac catheterisation laboratory and some in the intensive care unit following surgical procedures.
Others tested the patch while undergoing regular daily activities, such as cycling, raising arms and legs, doing mental arithmetic and even consuming energy drinks.
The patch was also tested while subjects changed posture by standing up from a sitting position.
Co-author Sheng Xu said that it was important to test the device in a variety of situations as blood pressure can be “all over the place” depending on a wide range of factors.
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