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KMID : 0378120020290020133
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Chungnam Medical Journal
2002 Volume.29 No. 2 p.133 ~ p.142
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FIR Digital Filter Design for Pulse Oximetry
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Lim Hyun-Soo
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Abstract
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Blood oxygen saturation(SpO_(2)) is an important clinical indicator of patient health. However. pulse oximeter is a complex system that can suffer from the problem of excessive noise. Noise reduction is important to get a precise pulse oximetry reading.
We attempted to reduce the noise in the raw signal and to develope an appropriate calibration curve for the pulse oximeter. We used an FIR 35 order Digital Low Pass Filter(LPF) with a signal preprocessor on a measured raw signal to effectively reduce the signal noise. Both applied preprocessor and non-applied preprocessor signals were investigated. By passing the two signals into the 35 order Low pass filter the applied non-preprocessor signal is distorted by peaking noise while the preprocessor signal retains its original characteristics. Therefore. the latter signal is suitable for an appropriate calibration R-curl-e for calculation of pulse oximetry. Application of the preprocessor to the raw signal and passing the signal into a 35 order LPF is appropiate. In this way a calibration curve for 2 pulse oximeter system can be developed. The formulas for SpO_(2) were derived from the calibration curve. These results are useful to obtain an accurate SpO_(2) value for a pulse oximeter system.
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KEYWORD
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Pulse Oximetry, SpO_(2), FIR LPF, Preprocessor, Noise reduction, R-curve
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