(38) VENTILATORY DYNAMICS IN FIREFIGHTERS DURING SIMULATED FIREGROUND TASKS PERFORMED AT A STANDARDIZED PACE

A self-contained breathing apparatus (SCBA) provides firefighters (FF) with clean air in potentially toxic environments. However, a SCBA’s supply is finite, and the duration ultimately depends on a FF ventilatory rate. Thus, ventilatory dynamics are relevant to air conservation and work capacity during emergency response.

Purpose: (1) To investigate the ventilatory dynamics of FF while completing simulated fireground tasks at a fixed pace; (2) To identify ventilatory characteristics associated with greater SCBA air consumption.

Methods: Incumbent FF (N=40) completed two randomized trials of a continuous air consumption drill (ACD) at a predetermined, standardized pace (i.e., 7.8 min) while wearing full turnout gear. During one trial, FF breathed through a self-contained breathing apparatus (ACD_SCBA) and the change in air pressure was recorded. During the other trial (ACD_VO2), FF wore a portable gas analyzer designed to capture all expired air. FF were instructed to avoid using breathing techniques that could alter ventilation. Minute ventilation (VE), oxygen consumption (relative and absolute; VO₂), the ratio of minute ventilation to oxygen consumption (VE/VO₂), tidal volume (TV), and respiratory frequency (Rf) data from ACD_VO2 were compared to air consumption data from ACD_SCBA using descriptive statistics, paired-samples t-tests, effect sizes (Cohen’s d), and correlations.

Results: Figure 1 displays the ventilatory parameters of FF completing the ACD_VO2. On average, FF consumed 1559±217 lb·in² (40±5%) during the ACD_SCBA. Aside from the ladder extension task time, there were no differences in ACD completion time between mask conditions (p=0.09, d=0.33). No additional differences in the testing environment or physiological strain existed between trials. Total SCBA air consumption was positively correlated with total ventilation (r=0.51; p=0.001), absolute VO₂ (r=0.45; p< 0.01), VE (r=0.50; p=0.001), and TV (r=0.34; p</em>=0.03), but not relative VO₂ (r=0.08; p</em>< 0.61), Rf (r=0.15; p=0.35), or VE/VO₂ (r=0.14; p=0.40).

Conclusions: Despite performing tasks at a fixed pace, there was considerable variability in ventilatory outcomes, likely due to differences in stature and economy. As expected, VE was related to total SCBA air consumption. Although VO₂ remained relatively steady throughout the drill, VE exhibited a gradual rise, reflecting decreased efficiency as the drill progressed. Further, predominantly anaerobic tasks (e.g., hoseline advance, forcible entry) were characterized by increases in Rf, whereas predominantly aerobic tasks (e.g., equipment carry, search) were characterized by increases in TV. TV was related to total air consumption, though Rf was not. PRACTICAL APPLICATIONS: Ventilatory dynamics appear to be influenced by the duration and types of tasks performed. Future research should investigate the efficacy of breathing techniques on air management, particularly during longer duration tasks of relatively low intensity.

Acknowledgements: None