The effects of chemical, nuclear, radiological medical training on first responders: dysfunctional heart rate variably leads to altered physiological and psychological response.

Abstract Background: While professionals working in chemical, biological, radiological, and nuclear (CBRN) environments have underlined the need to improve the psychological and operational safety of personnel, there are few data regarding the stress induced in responders who must wear CBRN equipment. These conditions are particularly restrictive, both due to the risk of exposure to life-threatening toxic agents, and the need to wear equipment that places demand on their psychological, cognitive, and physiological capacities. Inter-individual variability remains poorly understood. Current research recognizes that the activity of the parasympathetic system (PSS) can be used as an objective marker of stress adaptation, measured as heart rate variability (HRV). Methods:28 members of the Paris Fire Brigade medical team attended to three simulated scenarios requiring CBRN management of casualties. We examine: (i) anxiety, emotions, coping, body awareness, cognitive load, HRV, and exteroception impacts of working in CBRN environment; (ii) the role of PSS functioning in stress responses; and (iii) recovery. We recorded for three days: before the simulations (baseline), simulations’ day (pre- and post-training), and the following day. Results show: (i) a high level of anxiety at baseline (Median 51 [46;56]) which decreased between pre- and post-training (p = 0.02); (ii) a post-simulation decrease in negative affect (p = 0.03); (iii) a tendency to decrease in body awareness during simulation (p = 0.06), which returned to the initial level at follow-up (p = 0.07); and (iv) decrease in mean RR between baseline and post-simulation n°1 (p = 0.04), and between baseline and post-training (p= 0.01). Clustering analysis based on the post-training median RMSSD: (i.e., stress-adapted subject versus non-stress-adapted subject) shows that stress-adapted subject tends to have more positive affect (p=0.006), a higher mean RR (p = 0.014) and SDNN (p = 0.005). The autonomic nervous system (ANS) shows different kinetics: the PSS activity increases post simulation in stress-adapted subject, and collapse between baseline, pre- and post-training in non-stress-adapted subject (p = 0.002). The sympathetic activity tends to increase in stress-adapted subject between baseline, pre- and post-simulation and tend to decrease in non-stress-adapted subject. Conclusion: stress-adapted subject has a hardiness psycho-physiological response under CBRN stress.