A COMPARISON OF NOVEL COOLING METHODS FOR PREVENTION OF HYPERTHERMIA IN CBR RESPONDERS IN TROPICAL CONDITIONS
Ian Norton¹,², Matt Brearley², Terry Trewin³, Kirsten Hrabar¹
¹ Royal Darwin Hospital, Darwin, Australia
² National Critical Care & Trauma Response Centre, Darwin, Australia
³ Northern Territory Fire and Rescue Service
Aims: To assess the physiological and perceptual responses of health care workers to a CBR (chemical, biological, radiological) training exercise in tropical ‘wet season’ conditions, and to compare the effectiveness of four cooling methods.
Methods: 60 volunteer participants, all of whom were health care workers (predominantly doctors and nurses) were randomised into 4 cohorts (1 Shade; 2 Ice Vest; 3 Water Immersion; 4 Crushed Ice Ingestion) matched for body mass index (BMI). The exercise consisted of triaging, resuscitating, mobilising and decontaminating manikins while dressed in level 3 PPE (personal protective equipment) in field conditions (mean outdoor wet-bulb globe temperature of 31.4°C) for 30 minutes followed by removal of the PPE for 30 minutes of cooling; repeated 3 times. Cohort 2 wore ice vests under their PPE during the active phase, and then rested in the shade. During the cooling phase, cohort 1 rested quietly in the shade, cohort 3 were immersed in large tubs of water at 25°C and cohort 4 ingested 7.5mL.kg-1 body mass of crushed ice. All 4 groups had ad libitum access to fluids. An ingestible telemetry pill permitted measurement of core temperature throughout the exercise, while tympanic temperature, heart rate, blood pressure, subjective thermal sensation and thermal discomfort ratings were recorded periodically throughout the cooling phase.
Results: The peak core body temperature of 40.8°C was observed, with 3 participants recording temperatures above 40.4°C during the study. Ice vests worn during work periods and immersion in water during rest periods were found to be substantially more effective than resting at ambient temperature in shade, or drinking crushed ice.
Conclusions: This study, the first of its kind, was carried out in tropical conditions in the field, with health care workers wearing impermeable PPE during a realistic CBR incident scenario. We confirmed that CBR responders are at risk of hyperthermia in these conditions. We are able to suggest work rest ratios that offer safe working conditions for a range of responders in a tropical environment.
Contact Disaster Medical Research Manager, Matt Brearley for more information via firstname.lastname@example.org, (08) 89226422 or 0420899399.