This article is part of a series on Wearable Technology in Physical Medicine and Rehabilitation, edited by Paolo Bonato.

Research

Reduction of motion artifact in pulse oximetry by smoothed pseudo Wigner-Ville distribution

Yong-sheng Yan^* , Carmen CY Poon and Yuan-ting Zhang

Joint Research Center for Biomedical Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong

author email corresponding author email* Contributed equally

Journal of NeuroEngineering and Rehabilitation 2005, 2:3doi:10.1186/1743-0003-2-3

Published:	1 March 2005

Abstract

Background

The pulse oximeter, a medical device capable of measuring blood oxygen saturation (SpO2), has been shown to be a valuable device for monitoring patients in critical conditions. In order to incorporate the technique into a wearable device which can be used in ambulatory settings, the influence of motion artifacts on the estimated SpO2 must be reduced. This study investigates the use of the smoothed psuedo Wigner-Ville distribution (SPWVD) for the reduction of motion artifacts affecting pulse oximetry.

Methods

The SPWVD approach is compared with two techniques currently used in this field, i.e. the weighted moving average (WMA) and the fast Fourier transform (FFT) approaches. SpO2 and pulse rate were estimated from a photoplethysmographic (PPG) signal recorded when subject is in a resting position as well as in the act of performing four types of motions: horizontal and vertical movements of the hand, and bending and pressing motions of the finger. For each condition, 24 sets of PPG signals collected from 6 subjects, each of 30 seconds, were studied with reference to the PPG signal recorded simultaneously from the subject's other hand, which was stationary at all times.

Results and Discussion

The SPWVD approach shows significant improvement (p < 0.05), as compared to traditional approaches, when subjects bend their finger or press their finger against the sensor. In addition, the SPWVD approach also reduces the mean absolute pulse rate error significantly (p < 0.05) from 16.4 bpm and 11.2 bpm for the WMA and FFT approaches, respectively, to 5.62 bpm.

Conclusion

The results suggested that the SPWVD approach could potentially be used to reduce motion artifact on wearable pulse oximeters.