(7) CAREER STRUCTURAL FIREFIGHTER’S IMMUNE, BIOCHEMICAL, AND CORTISOL RESPONSES TO A FIVE-DAY SMOKE DIVER TRAINING PROGRAM

Purpose: Smoke diver training is a five-day live fire simulation course designed to push firefighters to their physical and mental limits. During the course, firefighters work independently and as a team to complete live fire rescue evolutions, rescuing weighted mannequins and fire instructors in different scenarios. These programs present a unique opportunity to study changes in immunological and cortisol responses, and blood chemistry following repeated live fire events. While some studies have investigated changes in immune function and blood chemistry, these studies did not include a baseline or measure changes in cortisol. The purpose of this study was to investigate the stress responses of firefighters during smoke diver training in the form of immunological, biochemical, and cortisol responses. Methods: 24 firefighters (age: 31.4±6.4 yrs, height: 179.1±6.4 cm, weight: 93.7±14.2 kg, body fat percentage (BF%): 19.0±8.0%) attending a smoke diver training course were recruited to participate in this study. Blood was drawn at three timepoints: Monday (Day 1) morning before beginning any training for the week, Thursday (Day 4) morning before training began for the day, and within 30 minutes of completing the last of their training drills for the day (Day 4). Whole blood samples were processed through a hematology analyzer for complete blood counts. Plasma, isolated from the whole blood, was then used for further analysis using a blood chemistry analyzer, and serum cortisol levels were measured using an ELISA kit. Statistical analyses were conducted using repeated measures ANOVA with Bonferroni corrections to test for changes in cortisol and blood chemistry and hematology variables. Statistical significance was set at an alpha level of 0.05. Results: Only 16 of the 24 firefighters completed the training. Of these, a subsample 14 (age: 31±6 yrs, height: 179.4±6.3 cm, weight: 86.2±7.6 kg, BF%: 14.6±6.1%) had a complete blood sample series, with 11 of them being assayed for serum cortisol levels. Between the first and final time points, there were significant decreases in erythrocytes (p <0.001, ES=0.628), platelets (p=0.002, ES=0.450), and serum cortisol concentrations (p <0.001, ES=0.579) but significant increases in leukocytes (p <0.001, ES=0.720), creatine kinase levels (p <0.001, ES=0.574), and blood urea nitrogen (BUN) levels (p=0.002, ES=0.384). Among leukocyte subspecies, there were significant increases in lymphocytes (p <0.001, ES=0.527), monocytes (p < 0.001, ES=0.537), and neutrophils (p < 0.001, ES=0.781). Conclusions: Firefighters undergoing smoke diver training experienced a significant inflammatory response as indicated by the decreases in cortisol and increases in leukocyte counts, particularly monocytes and neutrophils. The decrease in platelets suggests an ongoing response to vascular damage, while the increases in creatine kinase and BUN would suggest an increased risk of developing rhabdomyolysis. Practical Applications: Given the significant inflammatory response and identified risk of rhabdomyolysis in this study, healthcare professionals should work to integrate these findings into firefighter health management protocols. This should include routine monitoring of relevant biomarkers, proactive recovery strategies following fire calls, and targeted interventions for those in high-call-volume environments to mitigate internal damage and ensure long-term well-being. Acknowledgements: None