Pre-processing of Photoplethysmographic Waveform for Amplitude Regularization

Abstract

This study is aimed to develop a post-processing method to regularize amplitude of PPG waveforms and evaluate the performance of the algorithm. The proposed procedure for regularizing amplitude consists of extracting the signal envelopes based on time-domain filtering, generating a compensation curve, and reconstructing the waveform. The proposed technique was evaluated with respect to dispersion and waveform fluctuation by means of coefficients of variation (CV) and a scaling exponent of detrended fluctuation analysis (DFA). Other criteria included the detection performances of major features such as upper and lower fiducial points and maximum dV/dt. In developing this method, we used a clinical dataset that comprised 74,225 beats. By applying reconstruction algorithm, the %CV and the scaling exponent of DFA were significantly decreased from 115.4 to 71.4 and from 1.029 to 0.836, respectively in peak amplitude. In valley amplitude, they were also decreased from 38.3 to 13.2 and from 0.993 to 0.713, respectively. Moreover, sensitivity of maximum dV/dt point, upper and lower peak detection are increased by 8.50, 2.72 and 5.21% after reconstruction, respectively. Our results clearly showed that the proposed reconstruction technique could reduce amplitude fluctuation and improve detection of fiducial points.

Photoplethysmogram Analysis and Applications: An Integrative Review

“…In addition to noise reduction, pre-processing is also performed for signal enhancement purposes. Kim et al (2019) proposed an amplitude regularization technique using an envelope curve to reduce the fluctuation of PPG amplitude. Canac et al (2019) used a moving differentiation filter to sharpen PPG upslope and eliminate high-frequency noise.…”

“…In addition to restoring distorted parts, reconstruction of the PPG waveform can be performed to enhance the waveform. To equalize PPG amplitude fluctuations when severe fluctuations in the PPG baseline or amplitude occur, Kim et al (2019) proposed a method of compensating the PPG amplitude using an amplitude compensation curve generated from the envelope of the PPG waveform. Figure 7 shows an example of PPG waveform reconstruction.…”

“…Calculating the difference with the sample after a window size of a moving window (Canac et al, 2019) Enhancing upslope of the photoplethysmogram Curve fitting Amplitude normalization Eliminating non-stationary dynamics -Amplitude compensation curve (Kim et al, 2019) Detrending -32nd-order polynomial fitting (Selvaraj et al, 2011) respiration or other various causes, accurate detection becomes difficult. Shin et al (2009) proposed an adaptive threshold PPG peak detection method based on a dynamic threshold that tracks the signal amplitude and finds peaks at the maximum amplitude outside the refractory period.…”

Anti-motion imaging photoplethysmography via self-adaptive multi-ROI tracking and selection

“…} the raw IPPG signal t Signal j ( ) is a one-dimensional time series signal, where t T 0, , Î ¼ { } is the video frame index within a time window of T-length frames. The American Heart Association defined the measurement range of clinically approved HR monitors as between 30 and 210 bpm (Kim et al 2019). Thus, a finite impulse response (FIR) bandpass filter with a 0.5-3.5 Hz cut-off frequency is applied to the raw IPPG signal.…”