Research On Monitoring System Of Pulse Oxygen Saturation

Oxygen is the key material to human's life, and oxygen saturation is one of the important parameters reflecting oxygen delivery ability in human's blood. The non-invasive method detecting oxygen saturation can provide fast, direct, effective physiological parameters to doctors. But, in measuring blood oxygen concentration, some factors which can lead the monitor system to abnormal working. These factors include: the disturbance of environment noise, movement of patients, baseline drift of Pulse wave, signal value exceeding range of amplifier, and so on. How to get an accurate and reliable oxygen saturation value by non-invasive, economical ways is always concerned by researchers in biomedical engineering. This paper analysis the measuring principle of pulse oxygen meter and discusses the exiting technology of pulse oxygen meter.At first, this paper deeply introduces the concept of oxygen saturation and the pulse development process of pulse oxygen saturation meter. The theory and methods of pulse-type oxygen saturation detection are analyzed deeply in this paper, and the pulse oxygen saturation detection formula is deduced by means of the Lambert - Beer theory.Secondly, the monitoring system of Pulse oxygen saturation has been designed. Through the MSP430 as the explosion platform, on the research of hardware circuit design system, we developed the auto-gain control circuit, applied the adjustable integrating amplifier, and developed the adjustable control intercept circuit. On the research of software system, at first we applied the digital filtering dealing with the pulse signal from the hardware circuit. Then, we propose an adaptive de-noising method that combines multiple wavelet transform. Based on the deeply understanding of the LMS adaptive filter and wavelet transform principles, and use this method to deal with pulse signal. Finally we apply the moving average arithmetic to computing oxygen saturation.Finally, we made a profound research on the factors of the pulse oxygen saturation meter's measurement accuracy, such as blood flow small, the quality and quantity of hemoglobin and blood factors, and the interfering factors such as the interference of background light, electromagnetic interference and motion artifacts, and put forward some solutions to this problem.