title: On Time Domain Analysis of Photoplethysmogram Signals for Monitoring Heat Stress.
abstract: There are a limited number of studies on heat stress dynamics during exercise using the photoplethysmogram (PPG) and its second derivative (APG). However, we investigate the most suitable index from short PPG signal recordings for heat stress assessment. The APG waveform consists of a, b, c and d waves in systole and an e wave in diastole. Our preliminary results indicate that the use of the energy of aa area, derived from PPG signals measured from emergency responders in tropical conditions, is promising in determining the heat stress level using 20-s recordings. After examining 14 time domain features using leave-one-out cross-validation, we found that the aa energy extracted from PPG signals is the most informative feature for classifying heat-stressed subjects, with an overall accuracy of 79%. Moreover, the combination of the aa energy with the traditional Sensors 2015, 15 24717 heart rate variability index of heat stress (i.e., the square root of the mean of the squares of the successive aa intervals) improved the heat stress detection to an overall accuracy of 83%.
authors.affiliation: Electrical and Computer Engineering in Medicine Group, University of British Columbia and BC Children's Hospital, Vancouver, BC V6H 3N1, Canada. moe.elgendi@gmail.com.|Department of Computing Science, University of Alberta, Edmonton, AB T6G 2E8, Canada. moe.elgendi@gmail.com.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Elgendi
authors.affiliation: Media Lab, Massachusetts Institute of Technology, Boston, MA 02139, USA. fletcher@media.mit.edu.
authors.forename: Rich
authors.initials: R
authors.lastname: Fletcher
authors.affiliation: National Critical Care and Trauma Response Centre, Darwin, NT 0810, Australia. nortoni@who.int.
authors.forename: Ian
authors.initials: I
authors.lastname: Norton
authors.affiliation: National Critical Care and Trauma Response Centre, Darwin, NT 0810, Australia. matt.brearley@nt.gov.au.
authors.forename: Matt
authors.initials: M
authors.lastname: Brearley
authors.affiliation: School of Electrical and Electronic Engineering, University of Adelaide, Adelaide, SA 5005, Australia. derek.abbott@adelaide.edu.au.
authors.forename: Derek
authors.initials: D
authors.lastname: Abbott
authors.affiliation: Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia. n.lovell@unsw.edu.au.
authors.forename: Nigel H
authors.initials: NH
authors.lastname: Lovell
authors.affiliation: Department of Computing Science, University of Alberta, Edmonton, AB T6G 2E8, Canada. daes@ualberta.ca.
authors.forename: Dale
authors.initials: D
authors.lastname: Schuurmans
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D005385:Fingers; D057232:Global Warming; D006339:Heart Rate / Q000502:physiology; D018882:Heat Stress Disorders / Q000175:diagnosis*; D006358:Hot Temperature; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000379:methods; D017156:Photoplethysmography / Q000295:instrumentation / Q000379:methods; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation
keywords: affordable healthcare; global warming; thermal stress