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Sensors 2015, 15(10), 24716-24734;

On Time Domain Analysis of Photoplethysmogram Signals for Monitoring Heat Stress

Electrical and Computer Engineering in Medicine Group, University of British Columbia and BC Children's Hospital, Vancouver, BC V6H 3N1, Canada
Department of Computing Science, University of Alberta, Edmonton, AB T6G 2E8, Canada
Media Lab, Massachusetts Institute of Technology, Boston, MA 02139, USA
National Critical Care and Trauma Response Centre, Darwin, NT 0810, Australia
School of Electrical and Electronic Engineering, University of Adelaide, Adelaide, SA 5005, Australia
Graduate School of Biomedical Engineering, UNSW, Sydney, NSW 2052, Australia
Author to whom correspondence should be addressed.
Academic Editor: Alexander Star
Received: 23 June 2015 / Revised: 14 September 2015 / Accepted: 21 September 2015 / Published: 25 September 2015
(This article belongs to the Section Biosensors)
Full-Text   |   PDF [556 KB, uploaded 25 September 2015]   |  


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 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%. View Full-Text
Keywords: global warming; affordable healthcare; thermal stress global warming; affordable healthcare; thermal stress

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Elgendi, M.; Fletcher, R.; Norton, I.; Brearley, M.; Abbott, D.; Lovell, N.H.; Schuurmans, D. On Time Domain Analysis of Photoplethysmogram Signals for Monitoring Heat Stress. Sensors 2015, 15, 24716-24734.

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