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Effect of external dead volume on performance while wearing a respirator
A T Johnson1, W H Scott, C G Lausted
1Biological Resources Engineering, University of Maryland, College Park, MD 20742-5711, USA.
AIHAJ : a Journal for the Science of Occupational and Environmental Health and Safety
|November 9, 2000
Summary
Increased respirator dead volume significantly reduces work performance and comfort. Even small increases in dead volume, which rebreathers exhaled carbon dioxide, led to substantial declines in endurance and user satisfaction during strenuous activity.
Area of Science:
- Physiology
- Occupational Health
- Human Performance
Background:
- Respirator dead volume reintroduces exhaled carbon dioxide (CO2) into the breathing circuit.
- Inhaled CO2 acts as a respiratory stimulant and can have psychoactive effects.
- This rebreathing effect is hypothesized to negatively impact performance during respirator use.
Purpose of the Study:
- To quantify the impact of varying respirator dead volumes on performance times.
- To assess the effect of respirator dead volume on user-perceived comfort during strenuous work.
- To establish a relationship between dead volume magnitude and performance/comfort decrements.
Main Methods:
- Subjects performed treadmill walking at high intensity (80-85% VO2max).
- Six controlled levels of respirator dead volume (280 mL to 1,160 mL) were imposed.
- Performance time and subjective comfort ratings were recorded for each dead volume condition.
Main Results:
- A significant, linear decrease in performance time was observed with increasing dead volume.
- Breathing apparatus comfort also showed a linear decline as dead volume increased.
- Each 350 mL increase in dead volume corresponded to a 19% reduction in performance time and an 18% decrease in comfort.
Conclusions:
- Respirator dead volume demonstrably impairs physical performance and reduces user comfort.
- The magnitude of performance and comfort decrements is directly proportional to the dead volume.
- Minimizing dead volume in respiratory protective equipment is crucial for maintaining user endurance and well-being during demanding tasks.