A wearable hyperspectral PPG module using a compact and high-resolution microspectrometer allows continuous, cuff-free blood pressure monitoring with high accuracy by capturing spectral PPG signals and physiological changes during exercise.

Conventional cuff-based blood pressure (BP) monitoring methods have long been the standard in clinical practice, but they involve discrete measurements and cause discomfort due to physical movement restrictions. These limitations make them unsuitable for continuous monitoring, especially in daily life or during physical activities. Cuffless alternatives have emerged as potential solutions, but most require bulky or rigid sensors that must be adhered to the skin, leading to discomfort during movement and limiting their practicality in dynamic environments.

Wearable devices, such as smartwatches, have recently adopted photoplethysmography (PPG) to estimate blood pressure noninvasively. These devices typically use a small number (typically 1 to 4) of wavelengths to measure blood volume and flow changes, offering some advantages with regard to mobility. However, their BP estimation accuracy remains poor, and they are unable to provide continuous, high-fidelity monitoring due to limited spectral resolution and signal variability during motion.

To overcome these challenges, a research team at KAIST developed a wearable blood pressure sensor based on hyperspectral photoplethysmography (HS-PPG). This new technology utilizes a novel, ultrathin, high-resolution microspectrometer capable of capturing PPG signals across as many as 50 distinct wavelengths. The HS-PPG module measures subtle spectral variations in the blood flow and enables precise calculation of the arteriolar pulse transit time (aPTT), a critical parameter for accurate BP estimations. The compact form factor of the module also supports integration into wrist-wearable devices.

The research team achieved continuous measurements of the BP, heart rate, and respiratory exchange ratio (RER) during exercise. The BP estimation demonstrated a coefficient of determination (R²) of up to 0.95 during recovery from exercise-induced hypertension—significantly outperforming conventional methods, which typically yield R² values around 0.75. This work highlights the strong potential of HS-PPG for high-accuracy, noninvasive, and continuous cardiovascular monitoring in everyday settings. This study demonstrates the potential of the wearable hyperspectral PPG sensor as a valuable tool for monitoring blood pressure during physical activity and for tracking its recovery based on newly acquired data from exercise-induced hypertension experiments. It serves as evidence that hyperspectral PPG technology can play a key role in dynamic, real-time BP monitoring. This technology is expected to make a significant contribution to the future of personalized digital healthcare.