Physiologic Strain during Treadmill Electrocardiography in the Medical Evaluation of Candidates for Hazardous Materials Duty, with and without Added Heat StressLawrence W Raymond*
Director of Occupational and Environmental Medicine, Carolinas Health Care System, Charlotte, NC, USA
- *Corresponding Author:
- W. Raymond L
Director of Occupational and Environmental Medicine
Carolinas Health Care System, Charlotte, NC
Professor of Family Medicine
University of North Carolina at Chapel Hill, USA
E-mail: [email protected]
Received Date: October 09, 2014; Accepted Date: October 28, 2014; Published Date: November 04, 2014
Citation : Raymond LW (2014) Physiologic Strain during Treadmill Electrocardiography in the Medical Evaluation of Candidates for Hazardous Materials Duty, with and without Added Heat Stress. Emerg Med (Los Angel) 4:224. doi:10.4172/2165-7548.1000224
Copyright: © 2014 W. Raymond L, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
added heat stress as part of medical evaluation for hazardous materials (hazmat) work requiring protective ensembles which block evaporative and convective heat transfer. Also, to extend comparison of PSI versus published values from hazmat simulations. Methods: Candidates for hazmat duty (N=203) underwent maximal, symptom-limited Bruce protocol treadmill electrocardiography (standard Bruce test wearing gym clothes, SBT) during which changes in tympanic temperature (TT) and heart rate (HR) enabled calculation of PSI. A subgroup of candidates (N=39) later performed a second Bruce test, wearing novel, inexpensive apparel chosen to impede dissipation of metabolic heat (Hot Bruce test, HBT). Thermal discomfort was gauged using the Young index (4, neutral; 8, maximal discomfort). Results: SBT duration was 12.2 ± 2.6 SD minutes and the rise in TT and PSI averaged 0.5 ± 0.4ÃÂC and 5.9 ± 1.1, respectively. The rate of rise of TT was 0.038ÃÂC per min. of treadmill exertion. In the subgroup of 39 candidates, HBT duration was 13.7 ± 3.3 min. (p>0.05). TT rose more after HBT than SBT: 1.3 ± 0.7ÃÂC vs. 0.5 ± 0.4ÃÂC (p<0.001). The rate of rise of TT during HBT was 0.10ÃÂC per min. and was associated with greater physiological strain (PSI=7.4 vs. 6.2, p<0.001). The Young index was 6.2 ± 0.8 for SBT vs. 7.3 ± 0.6 (p<0.001) for HBT. Maximal heart rate was 181 bpm during both SBT and HBT. Conclusions: 1. The rate of rise of TT–0.038ÃÂC per min. of SBT treadmill exertion -- is similar to that of two smaller studies, but less than the only other published report. 2. PSI during HBT exceeded that from SBT and was similar to PSI observed during hazmat simulations, suggesting that HBT, which also induced heavy sweating and thermal discomfort, may be more appropriate than SBT in the medical evaluation of hazmat candidates.