Abstract
Tissue oxygenation evaluation is an essential element in the management and understanding of patient care. This evaluation requires measurement of hemoglobin concentration and its oxygen saturation in the blood. The current study proposed the principal equation for simultaneous optical measurement of hemoglobin concentration, oxygen saturation, and water percentage in the blood. In this equation, the absorption coefficient of hemoglobin for the light of wavelength λ (μaλ) is expressed using the hemoglobin oxygen saturation (SO2), hemoglobin concentration ([Hb]), water percentage in the blood (fw), molar extinction coefficient (ε) for the light of wavelength λ for oxygenated hemoglobin and deoxygenated hemoglobin, and the absorption coefficients of water (μaλwater) for the light of wavelength λ. Thereafter, a total of 125 arbitrary values of μaλ were set by introducing various SO2, [Hb], and fw values in the equation with 125 different combinations. We observed that all the combinations of SO2, [Hb], and fw values could be reconstituted from the corresponding μaλ values using the Nelder–Mead method, a heuristic optimization technique, with the principal equation. However, this was only possible when ε and μaλwater values were used for light of specific wavelengths, i.e., light wavelengths that were absorbed by oxygenated and deoxygenated hemoglobin and water. This result suggests that hemoglobin concentration, oxygen saturation, and water percentage in the blood may be estimated from the hemoglobin absorption coefficient values via the optimization method with the proposed principal equation.
