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. 2018 May 1:5:180076.
doi: 10.1038/sdata.2018.76.

An optimal filter for short photoplethysmogram signals

Yongbo Liang  1   2   3 , Mohamed Elgendi  1   4   5 , Zhencheng Chen  2   3 , Rabab Ward  1
Affiliations

An optimal filter for short photoplethysmogram signals

Yongbo Liang et al. Sci Data. .

Abstract

A photoplethysmogram (PPG) contains a wealth of cardiovascular system information, and with the development of wearable technology, it has become the basic technique for evaluating cardiovascular health and detecting diseases. However, due to the varying environments in which wearable devices are used and, consequently, their varying susceptibility to noise interference, effective processing of PPG signals is challenging. Thus, the aim of this study was to determine the optimal filter and filter order to be used for PPG signal processing to make the systolic and diastolic waves more salient in the filtered PPG signal using the skewness quality index. Nine types of filters with 10 different orders were used to filter 219 (2.1s) short PPG signals. The signals were divided into three categories by PPG experts according to their noise levels: excellent, acceptable, or unfit. Results show that the Chebyshev II filter can improve the PPG signal quality more effectively than other types of filters and that the optimal order for the Chebyshev II filter is the 4th order.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1. A box plot of the signal quality index of raw photoplethysmogram signals.
Figure 2
Figure 2. A stacked histogram of normalized signal quality index (SQI) values for all filter types and orders.
The SQI was calculated using skewness.
Figure 3
Figure 3. A comparison of raw and filtered photoplethysmogram (PPG) waveforms in G1, G2, and G3 classes.
The skewness signal quality index values are shown for the raw PPG waveform (black color), the 4th-order Cheby II (red color), and 4th-order Butterworth (blue color) filters.
Figure 4
Figure 4. Photoplethysmogram waveform classifications.
Note, the SQI here is calculated using the skewness.
Figure 5
Figure 5. The photoplethysmogram study flowchart.
PPG stands for photoplethysmogram; SQI stands for signal quality index.
See this image and copyright information in PMC

References

Data Citations

    1. Liang Y., Liu G., Chen Z., Elgendi M. 2017. figshare. https://doi.org/10.6084/m9.figshare.5459299.v2 - DOI

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