Physiological Response to Firefighting: Air Consumption and Work Output

This article examines the physiological responses of firefighters during simulated firefighting activities, focusing on air consumption, work output, and the impact of physical fitness and equipment.

Physiological Demands of Firefighting

• Firefighting involves significant physical exertion, leading to increased air consumption and cardiovascular strain due to the need for oxygen during strenuous tasks.
• The self-contained breathing apparatus (SCBA) limits air supply, necessitating an understanding of how firefighting tasks, gear, and fitness levels affect performance and safety.
• Key physiological responses include increased heart rate, stroke volume, and minute ventilation, which are essential for meeting the oxygen demands of working muscles.

Impact of Firefighting Activities

• Studies show that firefighters experience rapid increases in heart rates and core temperatures during simulated activities like stair climbing, hose advancing, searching, and overhauling.
• In a controlled environment, firefighters reached near-maximal heart rates (180-185 bpm) and significant increases in core temperature after just 14 minutes of activity.
• Peak oxygen consumption varied by activity, with stair climbing demanding the most oxygen (8.1 METs) and overhaul requiring the least (5.5 METs).

Air Consumption and SCBA Efficiency

• The standard 30-minute SCBA cylinder holds about 1,275 liters of air, which can be consumed in approximately 14-17 minutes at peak ventilation rates.
• Average minute ventilation during activities was lower than peak rates, reflecting the intermittent nature of firefighting tasks.
• Firefighters’ ability to sustain high work output diminishes over time, particularly when transitioning to a second round of activities without adequate rest.

Effects of Extended Operations

• In studies simulating extended firefighting operations, firefighters showed decreased oxygen consumption and work output during a second round of activities, indicating fatigue.
• Heart rates remained high, but oxygen consumption dropped significantly across all activities, demonstrating that firefighters cannot maintain the same intensity over prolonged periods.
• Firefighters with higher body mass indexes (BMI) and lower fitness levels were more likely to experience fatigue and reduced performance.

Influence of SCBA Weight

• The weight of the SCBA affects operational capacity; heavier SCBAs led to shorter times until firefighters needed to exit due to fatigue.
• Average exit times decreased as SCBA weight increased, highlighting the importance of equipment weight on performance during firefighting operations.

Recommendations for Fireground Operations

• Firefighters should be monitored closely for physiological strain, especially after using two SCBA bottles or during extended operations.
• NFPA 1584 guidelines suggest that firefighters should report to rehabilitation after significant work to recover from the physiological demands of firefighting.
• Officers and incident commanders should consider the cumulative effects of fatigue and the reduced operational capabilities of firefighters who have already engaged in strenuous activities.

Conclusion

• Understanding the physiological responses to firefighting tasks is crucial for improving safety and efficiency on the fireground.
• Firefighters’ fitness levels, equipment weight, and the nature of the tasks performed significantly influence their performance and ability to sustain work output during operations.

Read the Full Article: Physiological Response to Firefighting: Air Consumption and Work Output, by Richard Kesler, Gavin Horn and Denise Smith