Proposal for alert threshold for stop activity to improve firefighters' occupational safety based on heart rate variability analysis

As firefighting is a highly stressful occupation and is performed under severe situations, understanding the physical state and activity capabilities of individual firefighters is essential for improving occupational safety management for firefighters. To examine how physiological information such as oxygen uptake and blood lactate levels and biological information such as heart rate and respiratory rate change during firefighting activities, we conducted six types of tests, including tests in which the imposed load gradually increases over time from a low to a high level, tests in which the constant load intensity repeats over time, a test that simulates actual firefighting activities, and a field test for endurance training. Based on an evaluation of the load degree on the cardiopulmonary function, which was determined from the change in both heart rate and proposed parameter reflecting respiratory metabolism state, a management methodology is proposed that determines when firefighters should stop a firefighting activity and take a break is proposed. The parameter representing respiratory metabolism state is determined by a frequency analysis of the heart-rate variability of the electrocardiographic information. The alert threshold is determined based on the results obtained in the simulated firefighting activity test and its effectiveness is validated in an endurance test performed in an outdoor and by a bicycle ergometer test. We present a method to estimate the minimum resting-time required for a firefighter undergoing continued highload activities, based on blood lactate level attenuation properties, but inferred from heart-rate signals.

Automated summary

Understanding the physical state and activity capabilities of individual firefighters is crucial for occupational safety management in firefighting. Tests were conducted to examine physiological and biological changes during firefighting activities, leading to a proposed methodology for determining when firefighters should take a break. The effectiveness of the methodology was validated through simulated firefighting tests and endurance training.