Frequency analysis of resting state muscles hemodynamics to assess endothelial activity.

The endothelium is responsible for fundamental processes such as blood vessel tone, and oxygen extraction. Some diseases such as respiratory diseases can affect endothelium functions, causing severe damage to the organisms. Previous studies demonstrated that near-infrared spectroscopy (NIRS) combined with vascular occlusion tests (VOT) allows assessing endothelial activities, and helps discriminate the progression of respiratory disease as acute respiratory distress syndrome. The VASCOVID project (Horizon 2020 European project) aims to evaluate the endothelial health of intensive care unit patients by exploiting VOT combined with new diffuse optical spectroscopies (DOS) technologies: time domain NIRS and diffuse correlation spectroscopy that allow measuring absolute hemoglobin concentration oxygen saturation and blood flow index. In the framework of this project, we studied a new strategy to evaluate endothelial activities by analyzing the frequency response of resting state blood flow. We observed that healthy subjects show peaks in the power spectral density at very low frequencies associated with endothelium functions, demonstrating the great potential of DOS frequency analysis.