Noninvasive assessment of regional and temporal variations in tissue oxygenation by near-infrared spectroscopy and imaging

A combination of near-infrared spectroscopy and discrete wavelength near-infrared imaging is used to noninvasively monitor the forearm during periods of restricted blood outflow (venous outflow restriction) and interrupted blood inflow (ischemia), Multivariate analysis of image and spectral data time courses was used to identify highly correlated spectral and regional domains, while fuzzy C-means clustering of image time courses was used to reveal finer regional heterogeneities in the response of stressed tissues, Localized near-infrared spectroscopy was used to investigate the magnitude of the bulk changes in the tissue optical properties and the variation in tissue oxygenation saturation during venous outflow restriction and complete forearm ischemia, The imaging and spectroscopic analyses revealed highly localized regional variations in tissue oxygen saturation during forearm ischemia as compared to the more diffuse and global response of the forearm during venous outflow restriction.