The Pulse Oximetry System Based On The Diffuse Theory

Oxygen saturation plays an important role in monitoring of patients in clinical surgery, neonates and premature infants, replying indicators of human body and so on. Pulse oximeter is used widely in hospital and daily life. However, the inherent limitations of its principles leave space for improvement in veracity, accuracy and stability of the results. We want to make improvement upon the theoretical model of pulse oximeter by replacing the Lambert-Beer's law with photon diffusion theory. We set up pulse oximeter based upon DSP TMS320F2812. Our work is briefly divided into five sections.Firstly, a digital pulse oximeter system is designed. All the signal processing work is allocated to DSP in order to guarantee the accuracy and stability of the measuring results.Secondly, diffusion equation (DE) for infinite tissue layer slab model is applied to obtain oxygen saturation which compared to the result of lambert-beer theory. Fittingpolynomial fits calibration curve describing the relationship which obtained by DE between R and oxygen saturation.Thirdly, in the software design portion, DSP achieves the functions of time delay, interruption, analog-digital conversion, characteristic point extraction and motion artifact elimination to calculate oxygen saturation.Fourthly, in the hardware design portion, a voltage conversion circuit, a low-pass filter circuit, a ambient light removal circuit and et al. are designed to guarantee the easy and convenient of the system and accuracy of effective information.Fifthly, in vivo measurement of blood oxygen and phantom measurement of blood oxygen experiments proved that oxygen saturation derived from DE correspond to the situation of measuring objects and can detective lower oxygen saturation.