Applying new dynamic models to near-infrared spectroscopy measurements of cerebral changes

This work advances biophotonics and computational modeling for real-time monitoring of cerebral physiology during extreme systemic disturbances, including cardiac arrest and carotid artery occlusion. Multimodal optical measurements near- infrared spectroscopy (NIRS), diffuse correlation spectroscopy (DCS), and laser Doppler flowmetry (LDF)-are employed to characterize cerebral blood flow (CBF), cerebral blood volume (CBV), and the cerebral metabolic rate of oxygen (CMRO2) in porcine models undergoing profound ischemic challenges. These measurements provide continuous, minimally invasive access to microvascular perfusion and metabolic dynamics during rapid transitions in cerebral state. A central contribution is the application of a non-linear extension of the Coherent Hemodynamic Spectroscopy (CHS) model, a physics-based framework that captures light–tissue transport and oxygen exchange across arteriole, capillary, and venule compartments. When coupled with NIRS, DCS, and LDF measurements, the model enables non-invasive quantification of absolute CBF and CMRO₂ and resolves transient physiological responses throughout ischemia and reperfusion without contrast agents. The work further examines metabolic–vascular coupling by analyzing the relationship between CMRO₂ and the redox state of cytochrome c oxidase (rCCO), a mitochondrial biomarker derived from hyperspectral NIRS. Observed changes in CMRO2–rCCO coupling reflect shifts in mitochondrial oxygen utilization under severe metabolic stress, offering mechanistic insight into injury progression and recovery. These findings support the feasibility of CHS-based, continuous bedside monitoring as a clinically translatable approach for neurocritical care, while underscoring the need for further validation against independent reference standards.