Design of a flexible dynamic optical spectroscopic system for monitoring blood oxygenation status in the carotid artery

Monitoring the carotid artery in patients who are at high-risk for stroke is crucial for early detection of abnormalities and may improve personalized, point-of-care diagnostics. We have developed a flexible 3-D printed patch for dynamic optical spectroscopy to evaluate the total blood oxygenation within the carotid artery. Each patch consists of a sensing module and detection module measuring 25 mm × 20 mm and 21 mm × 20 mm, respectively, placed a maximum distance of 32 mm apart. The sensing module contains four sources at wavelengths of 670 nm, 750 nm, 808 nm, and 850 nm placed in a square configuration, and the detection module contains two photodiodes in a parallel orientation. During data acquisition, two probes were applied proximally to both the left and right carotid arteries in the neck, and two probes were also placed proximally to the right and left radial arteries in the wrists. Six healthy participants were instructed to perform breathing exercises, such as a single deep breath, continuous deep breaths, and a timed breath hold, with intervals of routine breathing between each activity. Blood oxygenation was continuously measured during the data acquisition protocol. Our study demonstrated consistent blood oxygen content between the left and right carotid and radial arteries across all breathing exercises. Additionally, during a breath hold, we observed a 0.3% and a 0.1% decrease in oxygen saturation in the radial and carotid arteries, respectively. These findings underscore the system's potential to detect disease-related variations in individual carotid arteries, facilitating early detection.