Physiological Response Of USAR-workers During Training In Extreme Hot Conditions

Abstract

Urban Search And Rescue (USAR) teams are often deployed in areas where the ambient conditions can be classified as 'extreme'. USAR operations often take several days in which team members work in irregular work shifts. The extreme conditions combined with the irregular work shifts involve high physical demands. Little is known about the physiological requirements of search-and-rescue tasks under extreme conditions over a prolonged period of time. PURPOSE: To evaluate the physiological responses of Dutch USAR-workers during a 4-day training period in the desert near Dubai (UAE). METHODS: The training period was divided in three parts: a 2 day adaptation period in the heat, 4 consecutive days of USAR training and a 2 day recovery period. During the adaptation period the activities as ordered by the training staff were observed by the research team. During the 4 day training period, 8 experienced USAR-workers (42.3±7.2 yr; BMI 27.0±3.7) were monitored. Core temperature (Tcore) and heart rate (HR) was measured with the EquivitalTM-system (Hidalgo Ltd., Cambridge UK). The percentage heart rate reserve (%HRR) as derived from HR was used as measure for the relative physical workload. Environmental conditions were measured and logged with a mobile weather station (QuestTemp 36, Oconomowoc, WI, USA) to calculate the Wet Bulb Globe Temperature (WBGT). RESULTS: During the adaptation period the rescue workers were ordered to stay outdoors as much as possible and be physically active in the heat. This resulted in a 10-15% prevalence of symptoms of heat related problems (headache, nausea, etc.). During the 4 day training period a mean WBGT-value of 27.4±3.6°C (range: 23.7-34.5°C) was measured. A mean core temperature during rescue activities of 38.0±0.3°C was measured. Individual values for Tcore exceeded 39.5°C. The mean workload was 'light to moderate' (between 20-40%HRR), but during some of the activities peak values of 80%HRR were calculated. On the final day of the training period one of the subjects was hospitalized due to severe heat illness. CONCLUSION: It is concluded that the training of the Dutch USAR-team took place under extreme environmental conditions. Although mean physiological responses were not extremely high, individual values pointed out that the USAR-workers were exposed to extreme high risks.