Physiological responses during graded treadmill exercise in chemical-resistant personal protective equipment

Background. As the likelihood of terrorist acts increases, prehospital personnel have been forced to train in the proper use of chemical-resistant personal protective equipment (PPE). This protective ensemble has been reported to be physiologically taxing for the wearer, imposing an additional thermal load resulting in hypohydration, hyperthermia, and reduced work time. Victim extrication, the rescue-the-rescuer role of the rapid intervention team and rapid self-extrication, typically requires high-intensity work that can be maintained only for short time intervals. The additional physiological burden imparted by the level C PPE during high-intensity work is unknown. Objective. We hypothesized that the added thermal burden resulting from work in PPE would shorten work time and result in a higher core temperature during incremental treadmill exercise. Method. In this prospective, crossover, laboratory study, EMS providers (n = 8, 5 male) completed a Bruce treadmill test on two occasions: once in a chemical-resistant coverall and air-purifying respirator (PPE) and once in shorts and t-shirt (CON). Oxygen consumption, vital signs, core and skin temperature, and perceptual measures of exertion, thermal sensation, and comfort were monitored throughout the test. Results. Subjects achieved maximal oxygen consumption and more than 90% of age-predicted maximum heart rate in both conditions. Heart rate, skin temperature, and measures of perceived exertion, comfort, and thermal sensation increased during the treadmill exercise but did not differ between the PPE and CON conditions. Core temperature increased in both the CON and PPE conditions (0.8 ± 0.5 vs. 0.7 ± 0.3, p = 0.40). Conclusion. High-intensity work in level C PPE is primarily limited by cardiovascular capacity. The thermal burden associated with this short bout of work in PPE (approximately 10 minutes) is not different than high-intensity work in short pants and cotton t-shirt. Consideration should be given to cardiorespiratory fitness when assigning providers to work in chemical-resistant PPE, especially on tasks that require high-intensity work.