A Non-invasive Detection Of Pulse Oxygen Saturation Based On NIRS

Oxygen saturation is important physiological parameters which could weigh if the oxygen supplied for body is enough, in the clinical,the oxygen often has to be detected, especially in the operation, it is especially important to detect if the patient is lack of oxygen,even it could threaten the life safety of patient serious.So it is important to detect oxygen saturation continuously, timely, exactly and reliably.At present, the detection for oxygen saturation based on NIRS could monitor non-invasively, continuously, timely, so it has good application value in the clinical,and comes to be a research hotspots.But this method has some deficiencies,for example,it has weak capacity of resisting disturbance,the SNR is lower, it is great influenced by individual difference, and so on, these restrict the precision of oxygen saturation to be improved.This paper designs a non-invasive detection system for pulse oxygen saturation based on NIRS technology. It could monitor the body's oxygen saturation timely, reliably and exactly, and provide effective information for doctor to make right diagnosis in the clinical,so it could get the oxygen saturation for explaining easily in the clinical.This system is built up by hardware circuit and software design. To acquisition the pulse wave,AD620 and MCU 89C52 is used as hardware circuit center. Software department is mainly used to process the collected pulse wave signal,and compute the value of oxygen saturation,as it is based on LabVIEW which is the virtual instrument software development platform. The main finishing works are as follows:1.Hardware circuit(1)The probe for detecting oxygen saturation has been designed, and it could restrain the background light and dark current and so on.The LED is controlled by the timing sequence, and the pulse wave signal is light modulated by the LED's driving circuit. (2)The circuit is made up of the instrument amplifier AD620,amplifier TL084,and selection chip C4053.It makes the pulse wave signal amplified, filtered, detached and demodulated, it improves the SNR greatly.(3) As the MCU 89C52 is the center, the timing control is made for light modulation, the signal is collected by AD converter MAX 195 and the collected signal is sent into computer by serial port.2.Software department(1)The program of serial port and MCU is designed to collect and send the pulse wave signal to computer for processing.(2) Based on LabVIEW, the digital lock-in amplifier is designed to make the signal demodulated, and the data is stored and processed.(3)The motion artifact in the oxygen saturation measurement is eliminated by adaptive filter based on the wavelet transform. This method could restrain the inevitable disturbance caused by movement, breath and so on in the measuring.3.Analysis of error and accuracyAs the value of Q, the value of oxygen saturation measured by the standard detection instrument for oxygen saturation makes this system fitted and scaled, and measures the testees'oxygen saturation, the result of measurement could satisfy the needs of the detection for oxygen saturation in the clinical.