Author(s): CHONG, L., YONG, X., ROSLIE, N., LEE, S.H., NISHA, V., KOH, J., ANG, J. , Institution: HOME TEAM SCIENCE & TECHNOLOGY AGENCY, Country: SINGAPORE, Abstract-ID: 1353

INTRODUCTION:
To detect, handle, and contain hazardous chemicals and toxins, Singapore Civil Defence Force Hazardous Materials (HazMat) specialists may be deployed multiple times in a single operation. Based on current standard operating procedures, the recommended rest period after each deployment differs depending if it is the first, second, or third deployment. An open question is how the cognitive and physiological performance of our HazMat specialists is affected by the different lengths of rest durations between deployments. This study presents the first attempt to systematically examine current practices, and to determine the optimal work-rest cycle (WRC) based on cognitive and physiological measures.
METHODS:
120 HazMat specialists were recruited and randomly assigned to Group 1 (15 minutes rest), Group 2 (30 minutes rest), or Group 3 (45 minutes rest) between two HazMat deployments. During the deployments, they don their personal protective equipment and breathing apparatus to perform tasks that mimic an actual incident. Cognitive and physiological measures were administered periodically before and twice after the HazMat deployments. The Psychomotor Vigilance Task and the Operation Span Task were used to measure vigilance and working memory (WM) respectively. Maximal and average heart rate (HR), body temperature, and oxygen saturation levels were taken as indication of physiological fitness. Self-reported measures, the Rating-of-Fatigue scale and the Borg Rating of Perceived Exertion scale were also administered.
RESULTS:
Findings suggest that while there is improvement in WM performance after the second deployment, this improvement was not proportional to the resting durations. The best performing group was Group 3 while the worst performing was Group 2. These two groups, however, had similar HR by the end of the experiment while HR for Group 1 remained slightly elevated. Conversely, while vigilance performance decreased after two deployments for all groups, Group 1 performed the worst and reported feeling the most fatigue and exertion after two.
CONCLUSION:
As WM after 45 minutes was found to be better than that after 30 minutes despite HR in both groups being similar, it seems that WM might be underpinned by a non-linear relation between arousal and performance. In addition, the non-linear changes in WM in contrast to the decrease in vigilance for all groups suggests that the different cognitive functions of WM and vigilance respond differently to the exertion and fatigue of two deployments.
This study highlights the importance of assessing both cognitive and physiological performance when designing WRC, especially where HazMat specialists are required to be physically fit to endure the bouts of rigorous tasks and maintain alertness to react quickly to ever-changing situations. Considering that there are differing roles and intensities during an actual operation, future studies could also explore varying task types and demands when designing the optimal WRC for HazMat response.