Physiologic Responses to Simulated Shipboard Firefighting Tasks

Introduction: Fire suppression can result in injury and death, with cardiac events being the leading cause of death of on-duty structural firefighters. Few data, however, are available regarding the physiologic responses to shipboard fires. Therefore, the purpose of this report was to determine physiologic responses of simulated shipboard firefighting tasks. Materials and Methods: Nineteen subjects (age: 24 ± 5 y, (Formula presented) O₂peak: 44.9 ± 7.2 mL · kg⁻¹ · min⁻¹) performed firefighting tasks in protective garments and breathing apparatus. After completing each task, heart rate (HR), core temperature (T_C), ratings of perceived exertion (RPE), and physiological strain index (PhSI) were measured. The tasks began with walking 80 m followed by carrying two 20 kg buckets up and down a flight of stairs. Subjects then completed circuits of lifting, striking, and pulling tasks in an environmental chamber heated to 40 °C, 41% relative humidity. The circuit was repeated until volitional fatigue, or if a stopping criterion was met. Results: Subjects were in the simulated shipboard firefighting protocol for 1432 ± 516 seconds. All measured variables increased over time (P ≤ .01) and HR, RPE, and T_C were different from baseline at all timepoints (P ≤ .04). PhSI was different from baseline starting at circuit 2 (P < .01). Baseline HR was 85 ± 13 bpm and increased to 188 ± 10 bpm at peak exertion (P < .01). Similar changes were seen for T_C (baseline: 36.8 ± 0.2 °C, peak: 37.9 ± 0.5 °C, P < .01), RPE (baseline: 1 ± 1, peak: 9 ± 1, P < .01), and PhSI (baseline: 4.0 ± 0.9, peak: 7.2 ± 1.2, P < .01). Conclusion: Simulated shipboard firefighting tasks caused considerable tachycardia and hyperthermia among subjects completing multiple rounds of work. Future research should consider appropriate work to rest ratios to ensure firefighter safety.