Frequency analysis of photoplethysmogram and its derivatives.
There are a limited number of studies on heat stress dynamics during exercise using the photoplethysmogram (PPG). We investigate the PPG signal and its derivatives for heat stress assessment using Welch (non-parametric) and autoregressive (parametric) spectral estimation methods. The preliminary results of this study indicate that applying the first and second derivatives to PPG waveforms is useful for determining heat stress level using 20-s recordings. Interestingly, Welch's and Yule-Walker's methods in agreement that the second derivative is an improved detector for heat stress. In fact, both spectral estimation methods showed a clear separation in the frequency domain between measurements before and after simulated heat-stress induction when the second derivative is applied. Moreover, the results demonstrate superior performance of the Welch's method over the Yule-Walker's method in separating before and after the three simulated heat-stress inductions.
Electrical and Computer Engineering in Medicine Group, University of British Columbia, Vancouver, British Columbia, Canada; Department of Computing Science, University of Alberta, Edmonton, Canada. Electronic address: moe.elgendi@gmail.com.
Mohamed
M
Elgendi
D-Lab, Massachusetts Institute of Technology, Boston, USA.
Richard R
RR
Fletcher
National Critical Care and Trauma Response Centre, Darwin, Australia.
Ian
I
Norton
National Critical Care and Trauma Response Centre, Darwin, Australia.
Matt
M
Brearley
School of Electrical and Electronic Engineering, University of Adelaide, Adelaide, Australia.
Derek
D
Abbott
Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia.
Nigel H
NH
Lovell
Department of Computing Science, University of Alberta, Edmonton, Canada.
Dale
D
Schuurmans
D000328:Adult; D005260:Female; D018882:Heat Stress Disorders / Q000517:prevention & control*; D006801:Humans; D008297:Male; D017156:Photoplethysmography / Q000379:methods*
Affordable healthcare; Heat stress; Hot environment