Hypertension affects nearly half of all adults in the U.S. and remains the leading cause of cardiovascular disease. Regular and accurate blood pressure monitoring is essential for managing this condition, but current methods require cumbersome cuffs and are limited to single-time-point measurements, often taken in clinical settings. These infrequent readings can miss important fluctuations and fail to reflect a person's true blood pressure throughout the day, particularly at night or during daily activities. This makes it difficult to detect conditions like masked hypertension, where readings in a clinic appear normal but are elevated elsewhere. A new noninvasive method has now demonstrated significantly improved accuracy in estimating blood pressure, offering a potential solution that eliminates the need for a cuff.

Researchers at Boston University (Boston, MA, USA), in collaboration with Meta Platforms’ Reality Labs (Menlo Park CA, USA), have developed a cuff-less blood pressure monitoring technique using Speckle Contrast Optical Spectroscopy (SCOS). SCOS is an optical imaging method that analyzes the speckle patterns created by coherent light scattering off tissue to measure blood flow. While SCOS has previously been used for brain and tissue monitoring, this is one of the first studies to apply it to blood pressure estimation. The research team developed a device that uses dual laser wavelengths (532 nm and 808 nm) to collect SCOS waveforms from different tissue depths and at a higher frame rate than other systems. This enabled them to capture fine time features associated with cardiovascular activity. Measurements were taken from the wrist and finger of 30 volunteers at rest and during a leg press exercise to induce changes in blood pressure. The team extracted features from blood flow and volume waveforms and used machine learning models to estimate blood pressure.

The study, published in Biomedical Optics Express, found that combining blood flow and volume information improved blood pressure prediction accuracy by up to 31% compared to models using volume alone (photoplethysmography). The model accurately estimated systolic blood pressure with a low average absolute error of 2.26 mmHg. Repeat testing several weeks later in 20 participants confirmed the sustained accuracy. The device's ability to measure both blood flow and volume at high temporal resolution enables frequent, noninvasive monitoring using the wrist or finger. These results open the door to wearable devices that could monitor cardiovascular health continuously and comfortably in daily life. The researchers now plan to miniaturize the SCOS system, embed data processing capabilities on the device, and test its performance during real-world use over longer periods.

“Hypertension affects nearly half of all adults in the US and is the leading cause of cardiovascular disease,” said Ariane Garrett, a doctoral student in Darren Roblyer’s lab at Boston University. “This research is a step towards a wearable device that would let people monitor their blood pressure anytime, without a cuff.”

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