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Physiological Responses of Medical Team Members to a Simulated Emergency in Tropical Field Conditions

Published online by Cambridge University Press:  29 January 2013

Matt B. Brearley*
National Critical Care and Trauma Response Centre, Darwin, Australia
Michael F. Heaney
Royal Darwin Hospital, Darwin, Australia
Ian N. Norton
National Critical Care and Trauma Response Centre, Darwin, Australia Royal Darwin Hospital, Darwin, Australia
Correspondence: Matt Brearley, PhD, BHMS (Hons), BBus National Critical Care and Trauma Response Centre Royal Darwin Hospital Rocklands Drive Tiwi, NT, Australia 0810 E-mail



Responses to physical activity while wearing personal protective equipment in hot laboratory conditions are well documented. However less is known of medical professionals responding to an emergency in hot field conditions in standard attire. Therefore, the purpose of this study was to assess the physiological responses of medical responders to a simulated field emergency in tropical conditions.


Ten subjects, all of whom were chronically heat-acclimatized health care workers, volunteered to participate in this investigation. Participants were the medical response team of a simulated field emergency conducted at the Northern Territory Emergency Services training grounds, Yarrawonga, NT, Australia. The exercise consisted of setting up a field hospital, transporting patients by stretcher to the hospital, triaging and treating the patients while dressed in standard medical response uniforms in field conditions (mean ambient temperature of 29.3°C and relative humidity of 50.3%, apparent temperature of 27.9°C) for a duration of 150 minutes. Gastrointestinal temperature was transmitted from an ingestible sensor and used as the index of core temperature. An integrated physiological monitoring device worn by each participant measured and logged heart rate, chest temperature and gastrointestinal temperature throughout the exercise. Hydration status was assessed by monitoring the change between pre- and post-exercise body mass and urine specific gravity (USG).


Mean core body temperature rose from 37.5°C at the commencement of the exercise to peak at 37.8°C after 75 minutes. The individual peak core body temperature was 38.5°C, with three subjects exceeding 38.0°C. Subjects sweated 0.54 L per hour and consumed 0.36 L of fluid per hour, resulting in overall dehydration of 0.7% of body mass at the cessation of exercise. Physiological strain index was indicative of little to low strain.


The combination of the unseasonably mild environmental conditions and moderate work rates resulted in minimal heat storage during the simulated exercise. As a result, low sweat rates manifested in minimal dehydration. When provided with access to fluids in mild environmental conditions, chronically heat-acclimatized medical responders can meet their hydration requirements through ad libitum fluid consumption. Whether such an observation is replicated under a harsher thermal load remains to be investigated.

BrearleyMB, HeaneyMF, NortonIN. Physiological Responses of Medical Team Members to a Simulated Emergency in Tropical Field Conditions. Prehosp Disaster Med. 2013;28(2):1-6.

Original Research
Copyright © World Association for Disaster and Emergency Medicine 2013 2013 World Association for Disaster and Emergency Medicine

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