Abstract
BackgroundThe 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.MethodsThe 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 DiscussionThe 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.ConclusionThe results suggested that the SPWVD approach could potentially be used to reduce motion artifact on wearable pulse oximeters.
Highlights
Wearable medical devices are capable of continuously monitoring an individual's vital signs in real time
The results suggested that the smoothed psuedo Wigner-Ville distribution (SPWVD) approach could potentially be used to reduce motion artifact on wearable pulse oximeters
SpO2 estimated from the SPWVD, weighted moving average (WMA) and fast Fourier transform (FFT) approaches differed from the reference by -1.07 ± 2.42%, -1.31 ± 3.58% and -1.42 ± 3.18%, respectively
Summary
Wearable medical devices are capable of continuously monitoring an individual's vital signs in real time. These devices need to have a low failure rate and must report minimal false alarms In other words, these devices are required to provide an accurate estimate of the monitored vital sign under normal daily life situations. These devices are required to provide an accurate estimate of the monitored vital sign under normal daily life situations This leads to the important topic on the reduction of motion artifacts [1,2,3,4]. The smoothed pseudo Wigner-Ville distribution (SPWVD) is investigated as a novel motion artifacts resistant approach for estimating one of the most important vital signs – the blood oxygen saturation level (SpO2). By assuming that the artifact is a linear addition to the pulsatile photoplethysmographic (PPG) signal, the original signal can be reconstructed from the corrupted signal [9-
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