(4) THE IMPACT OF A SIMULATED OCCUPATIONAL EXPOSURE ON FIREFIGHTERS’ WORKING MEMORY: PROJECT FIRE

Purpose: To evaluate the impact of a simulated occupational exposure on firefighters’ working memory and to assess the relationship of occupational exertion versus working memory performance. Methods: 28 structural firefighters (Age: 31.4±5.6 yr; Body fat: 20.1±6.1%; Experience: 8.9±6.0 yr) completed a set of standardized simulated occupational tasks in an environmental chamber (Dry bulb temperature: 32.4±0.7 deg C; Relative humidity: 48.5±3.3%) including stair ascent, ladder climb, equipment carry, victim rescue, and search. Working memory outcomes were assessed during familiarization, prior to (baseline) and immediately following the occupational exposure (0 min), and after 20 and 40 min of passive recovery. During recovery, firefighters were seated in front of a fan (air velocity: 10 m/s) under a covered outdoor structure (Dry bulb temperature: 28.2±1.3 deg C; Relative humidity: 75.8±9.6%). Specifically, the working memory assessment was composed of a set of simulated radio communications similar to what is heard while responding to a fireground emergency and while in rehabilitation. The assessment was scored as the number of correct responses relative to the total number of items (n=10; %). Two sets of radio communications were developed and one set was randomly assigned in block format to each firefighter. Rating of perceived exertion (RPE), dyspnea, thermal stress, tympanic temperature, systolic and diastolic blood pressure, and blood oxygenation were assessed at each time point. Continuous variables are reported as mean ± standard deviation, whereas ordinal variables are reported as median [interquartile range]. Cronbach’s alpha was used to assess test-retest reliability of the working memory assessment. A repeated measures ANOVA was used to evaluate changes in working memory over time. Partial eta squared (ηp2) and statistical power values are reported. Pearson and Spearman’s rho correlations were used to evaluate bivariate relationships with working memory for continuous and ordinal variables, respectively. Significance was set at p < 0.05. Results: Working memory was not impacted by the occupational exposure and was similar across all time points (F(3,81)=0.540, p=0.657, ηp2=0.020, Power=0.16). Subsequently, the test-retest reliability of the work memory assessment across all time points was ICC = 0.717. There were no significant correlations between working memory scores at 0 min post exposure (82.5±12.7% correct) versus RPE (r=-0.20, p=0.310, 4.0[3.8]), dyspnea (r=-0.19, p=0.346, 2.5[3.0]), thermal stress (r=0.16, p=0.412, 2.0[1.0]), systolic blood pressure (r=0.05, p=0.803, 124.9±11.9 mmHg), diastolic blood pressure (r< -0.01, p=0.989, 69.1±7.0 mmHg), tympanic temperature (r=-0.08, p=0.685, 37.9±0.4 deg C), and blood oxygen saturation (r=-0.02, p=0.905, 95.5±1.9%). Conclusions: These findings indicate that performing simulated fireground tasks in a warm environment did not impact working memory and that working memory performance was not associated with perceptual or objective measures of occupational exertion. Practical Applications: This work demonstrates that this novel occupational working memory assessment yields acceptable reliability and indicates that a simulated occupational exposure does not impact firefighters’ short term occupational recall ability. However, additional research is necessary to determine if other cognitive processes are impacted by occupational fatigue and/or heat exposure. Acknowledgements: This investigation was funded by the University of Kentucky’s College of Education, Singapore Civil Defence Force, and Home Team Science and Technology Agency.