Design of filter to reject motion artifact of pulse oximetry

The performance of the pulse oximeter, an instrument which non-invasively measures oxygen saturation in blood, is influenced by a patient's respiration or movement. Generally, the frequency band of the motion artifact signal generated from the patient's movement is overlapped with that of the patient's pulse wave which is measured by the received light sensor. Accordingly, it is difficult to filter the motion artifact of the pulse wave by using a filter which has a cut-off frequency that is fixed. In this study, the motion artifact is removed using the filter bank and the matched filter. Compared with traditional adaptive filter methods, the ratio variation is 50% lower than that of the moving average filter, allowing more stable measurement of oxygen saturation despite the patient's movement. (C) 2003 Elsevier B.V. All rights reserved.