Comparison of Cardiocirculatory and Thermal Strain of Male Firefighters During Fire Suppression to Exercise Stress Test and Aerobic Exercise Testing

Abstract

Firefighters face a highly increased risk of sudden cardiac death during fire suppression. Medical examinations and physical performance tests are used to screen endangered firefighters. The aim of this study was to determine cardiocirculatory and thermal strain during fire suppression in firefighters and compare it with the strain during medical and performance evaluations. Forty-nine young professional male firefighters were studied during a 30-minute fire operation (FO) in a large fire simulation plant. Measurements were obtained immediately before, during, and after the FO. During the FO, maximum heart rates of 177 +/- 23 beats/min were recorded on average, with 7 subjects exceeding the age-predicted maximum. Body core temperature increased by 0.9 +/- 0.5 degrees C (p <0.001), body weight decreased by 0.6 +/- 0.2 kg (p <0.001), and blood parameters changed accordingly. Sixteen percent of subjects developed asymptomatic postural hypotension. In an exercise stress test as part of the mandatory medical examination, subjects were limited to heart rates of 176 +/- 3.3 beats/min. They reached 155 +/- 13 beats/min during the annual aerobic exercise in turnout gear. During the FO, maximum heart rate was higher than during the stress test in 66% and higher than during the aerobic exercise in 84% of subjects. In conclusion, fire suppression caused an extreme cardiocirculatory strain, with high heart rates that were not sufficiently tested in medical examinations. To increase the yield of screening for firefighters at risk of death during fire suppression, the exercise should equal requirements in a real emergency; in other words, be limited by exhaustion or age-predicted maximum heart rate.