Researchers Turn to Continuous-Wave Radar for New Non-Invasive, Long-Term Blood Pressure Monitor

Researchers from Australia's Monash University have developed a new wearable blood pressure monitor, based on continuous-wave radar (CWR) technology, which they claim is considerably less invasive for long-term monitoring than the current state of the art.

“For close to a century, the health sector has used the cuff device to measure blood pressure. More invasive measures are used to monitor the continuous blood pressure of critically ill patients, which are uncomfortable and could potentially cause infection due to ischaemia,” says study lead Associate Professor Mehmet Yuce. "Clinicians still cannot continuously measure blood pressure during sleep, nor during times of activity such as walking or running. This means people with high, low or irregular blood pressure can’t get the critical information they need about the state of their health around the clock.

"A wearable device that can provide comfort and portability while people are going about their daily lives will be a significant development for the health sector in Australia and internationally."

The team's experimental blood pressure monitor dispenses with the usual cuff and the invasive systems previously used for long-term continuous blood pressure monitoring in favor of a system based on continuous-wave radar (CWR) and photoplethysmogram (PPG) sensors — the former worn on the sternum, the latter on the subject's left earlobe. Data from these sensors were used to calculate the pre-ejection period, the delay associated with the heart ejecting the blood — and the pulse transit time, then using those to estimate blood pressure.

The results, while not perfect, shows promise: The new system proved 93 percent accurate for subjects sitting or laying down, dropping to a still-impressive 83 percent accuracy for those performing exercise, in the cohort of 43 participants aged between 40 and 65.

"The CWR sensors present a low-power, continuous and potentially wearable system with minimal body contact to monitor aortic valve activities directly. Doctors would be interested to see such information for long-term better diagnosis of their patients," explains Professor Yuce. "Results of this study demonstrate the potential superiority of CWR-based PEP extraction for various medical monitoring applications, including blood pressure monitoring."

The team's paper has been published in the journal Nature Scientific Reports, and is available under open access terms from Monash University.