Mathematical model and device for noninvasive assessment of fractional oxygen saturation levels

The article considers the development of noninvasive diagnostic instruments relying on the interaction between incident optical radiation and the examined biological medium. The existing models for assessing oxygen saturation levels in transmitted light are shown to inadequately describe the interaction of optical radiation with biological tissue. Specifically, they do not take into account the absorption capacity of those blood fractions that do not participate in oxygen transport. Therefore, the results of measuring fractional oxygen saturation are characterized by low accuracy. A mathematical model was developed for assessing fractional oxygen saturation levels via the photometric transmitted-light method with the use of four optical sources having central wavelengths of 660, 805, 880, and 940 nm. The principle for selecting the spectral characteristics of artificial radiation sources is described. A functional block diagram of the device for noninvasive assessment of fractional oxygen saturation levels is presented, and its operating principles are outlined. A prototype of the proposed device and an existing pulse oximeter were used to experimentally assess the fractional oxygen saturation levels of 30 test subjects. The experiment shows that the relative error in measuring the level of fractional oxygen saturation by the prototype device is 0.71% lower than the measurement error of the certified device, which proves the effectiveness of the prototype. The obtained results apply to the field of medical technology and can be used to design devices for noninvasive assessment of physiological health indicators.