Evaluation of blood oxygen saturation in vivo from diffuse reflectance spectra

Abstract

A simple method to evaluate the hemoglobin oxygen saturation and relative hemoglobin concentration in a tissue from diffuse reflectance spectra in the visible wavelength range is put forward in this paper. It was assumed that while oxygenated and deoxygenated hemoglobin contributions to light attenuation are strongly variable functions of wavelength, all other contributions to the attenuation including scattering are smooth wavelength functions and can be approximated by Taylor series expansion. Based on this assumption, a simple, robust algorithm suitable for real time monitoring of the hemoglobin oxygen saturation in the tissue has been derived. This algorithm can be used with different fiber probe configurations for delivering and collecting light passed through the tissue. An experimental technique using this algorithm has been developed for in vivo monitoring during artery occlusion and in vitro monitoring of blood samples. The experimental results obtained are presented in the paper.

Influence of skin type and wavelength on light wave reflectance

“…Hemoglobin plays a major role on light absorption especially at the lower wavelengths. 44,50 The sensor then interprets the inverse of the absorption in relation to blood volume in the tissue. 49 By detecting the change in the fluctuation of hemoglobin in the radial artery, a PPG-based device is able to determine pulse rate.…”

Evaluation of Diffuse Reflectance in Multi-layered Tissue for High Intensity Laser Therapy

“…The diffuse reflectance is defined as the photon probability of re-emission from the inside of an infinite turbid medium per unit surface area. The photon trajectories through the tissue form a banana shaped region with the ends at the positions of the delivery and receiving fibers [19,20]. As the source-detector distance increases the average path length increases significantly while the average photon visit depth increases only slightly.…”

Novel method for early signs of clinical shock detection by monitoring blood capillary/vessel spatial pattern

“…Therefore, to find the solution of the complex system of equations, a Taylor series expansion is used [37]. Three wavelengths, l 0 , l 1 , and l 2 will be selected within the 20 nm wavelength range, because within this wavelength range, the contribution of the tissue absorber and scattering shows a smooth function of wavelength [23]. …”

“…As a result, the optical response of tissue strongly depends on the presence of blood and its relevant parameters, such as the oxygen state and haematocrit value [22]. This opens wide possibilities for optical diagnostics because physiologically relevant information about the tissues [22][23][24][25] can be determined in real time and non-invasively. Currently, pulse oxymetry [26], spectrophotometric method, NIR [27] and diffuse reflectance [28][29][30][31] are used for non-invasive blood oxygenation measurement.…”