A blood pressure test is the only way to detect hypertension. The usual method is with a blood pressure cuff on the arm. Another method is with a small device called a tonometer pressed against the skin over a blood vessel. For patients who are critically ill, health care providers can obtain even more accurate blood pressure readings by inserting a special tube inside an artery near the heart. This method is called cardiac catheterization.


To develop an accurate but less invasive technique, a research team at the University of California, San Diego, set out to develop a thin, wearable blood pressure sensor using ultrasound transducers. Transducers make high frequency sound waves that bounce off the blood vessel. The transducer then receives the echo patterns and sends them to a computer to create a representation of the vessel’s changing diameter, called a waveform. When calibrated to a patient’s blood pressure, these waveforms can be used to monitor changes in blood pressure.  The team engineered a stretchable, flexible device that can be worn as a skin patch. It has an array of ultrasound transducers so that the one that’s in the best position over an artery can be selected.