Comparison of Different Wavelengths for Estimating SpO2 Using Beer-Lambert Law and Photon Diffusion in PPG

Shifat Hossain, Tae-Ho Kwon, Ki-Doo Kim

Abstract: Photoplethysmography (PPG) is a non-invasive method of detecting blood volume changes in peripheral organ of human body. PPG is widely used to estimate blood oxygenation (SpO2) and thus this system requires at least two light sources to measure SpO2. In this research, these light sources' wavelengths in range of 300nm to 1000nm are compared and analyzed for which wavelength pair has the highest ratio. Both traditional Beer-Lambert law and Photon Diffusion theories are taken into consideration to assess the absorption and scattering effects of blood and tissues. And it is seen that, for the pair of violet-red wavelength ranges (378nm-417nm and 679nm-730nm), the ratio gets the highest value with or without scattering effects and will eventually produce more accurate estimation of blood oxygenation.