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. 2022 Sep;47(3):213-222.
doi: 10.1007/s10484-022-09549-z. Epub 2022 Jun 15.

Dynamic Phase Extraction: Applications in Pulse Rate Variability

Christopher H Li  1 , Franklin S Ly  2 , Kegan Woodhouse  2 , John Chen  2 , Zhuowei Cheng  3 , Tyler Santander  4 , Nirmit Ashar  3 , Elyes Turki  5 , Henry T Yang  2 , Michael Miller  4 , Linda Petzold  2   3 , Paul K Hansma  5   6
Affiliations

Dynamic Phase Extraction: Applications in Pulse Rate Variability

Christopher H Li et al. Appl Psychophysiol Biofeedback. 2022 Sep.

Abstract

Pulse rate variability is a physiological parameter that has been extensively studied and correlated with many physical ailments. However, the phase relationship between inter-beat interval, IBI, and breathing has very rarely been studied. Develop a technique by which the phase relationship between IBI and breathing can be accurately and efficiently extracted from photoplethysmography (PPG) data. A program based on Lock-in Amplifier technology was written in Python to implement a novel technique, Dynamic Phase Extraction. It was tested using a breath pacer and a PPG sensor on 6 subjects who followed a breath pacer at varied breathing rates. The data were then analyzed using both traditional methods and the novel technique (Dynamic Phase Extraction) utilizing a breath pacer. Pulse data was extracted using a PPG sensor. Dynamic Phase Extraction (DPE) gave the magnitudes of the variation in IBI associated with breathing [Formula: see text] measured with photoplethysmography during paced breathing (with premature ventricular contractions, abnormal arrhythmias, and other artifacts edited out). [Formula: see text] correlated well with two standard measures of pulse rate variability: the Standard Deviation of the inter-beat interval (SDNN) (ρ = 0.911) and with the integrated value of the Power Spectral Density between 0.04 and 0.15 Hz (Low Frequency Power or LF Power) (ρ = 0.885). These correlations were comparable to the correlation between the SDNN and the LF Power (ρ = 0.877). In addition to the magnitude [Formula: see text], Dynamic Phase Extraction also gave the phase between the breath pacer and the changes in the inter-beat interval (IBI) due to respiratory sinus arrythmia (RSA), and correlated well with the phase extracted using a Fourier transform (ρ = 0.857). Dynamic Phase Extraction can extract both the phase between the breath pacer and the changes in IBI due to the respiratory sinus arrhythmia component of pulse rate variability ([Formula: see text], but is limited by needing a breath pacer.

Keywords: Lock-in amplifier; Photoplethysmography; Pulse rate variability; Respiratory sinus arrhythmia.

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