Comparison of active cooling devices with passive cooling for rehabilitation of firefighters performing exercise in thermal protective clothing: A report from the fireground rehab evaluation (FIRE) trial

Background. Thermal protective clothing (TPC) worn by firefighters provides considerable protection from the external environment during structural fire suppression. However, TPC is associated with physiologic derangements that may have adverse cardiovascular consequences. These derangements should be treated during on-scene rehabilitation periods. Objective. To examine heart rate and core temperature responses during the application of four active cooling devices, currently being marketed to the fire service for on-scene rehabilitation, and compare them with passive cooling in a moderate temperature (approximately 24°C) and with an infusion of cold (4°C) saline. Methods. Subjects exercised while they were wearing TPC in a heated room. Following an initial exercise period (bout 1), the subjects exited the room, removed the TPC, and for 20 minutes cooled passively at room temperature, received an infusion of cold normal saline, or were cooled by one of four devices (fan, forearm immersion in water, hand cooling, or water-perfused cooling vest). After cooling, the subjects donned the TPC and entered the heated room for another 50-minute exercise period (bout 2). Results. The subjects were not able to fully recover core temperature during a 20-minute rehabilitation period when provided rehydration and the opportunity to completely remove the TPC. Exercise durations were shorter during bout 2 when compared with bout 1 but did not differ by cooling intervention. The overall magnitudes and rates of cooling and heart rate recovery did not differ by intervention. Conclusions. No clear advantage was identified when active cooling devices and cold intravenous saline were compared with passive cooling in a moderate temperature after treadmill exercise in TPC.