Effect of continuous cooling on inhibition and attention while wearing firefighter’s PPE in a hot environment

Abstract

Firefighting is physically and mentally strenuous, requiring rapid, appropriate decision-making in hot environments. Intact cognitive function is imperative to firefighters’ effectiveness and safety. The study purpose was to investigate the effect of hyperthermia and the effect of body cooling on sustained attention and response inhibition while wearing firefighters’ personal protective ensembles after exercise in a hot environment. Twelve healthy males were recruited to participate in two randomly assigned exercise sessions (walking on a treadmill for 40 min at 40% $\dot{V}$ O_2max while wearing firefighter’s protective ensemble) in a hot environment: control (no cooling) and intervention (cooling). For intervention sessions, a cooling garment was worn underneath firefighter’s protective ensemble and infused with 18 °C water supplied by an external water circulator. Participants performed a computerized Go/No-Go (a measure of cognitive function) test three times at baseline and post-exercise for each experimental session. Participants completed baseline testing while wearing cotton athletic clothing. The exercise continued until the core temperature reached ∼39 °C (for all subjects regardless of cooling or non-cooling experimental sessions). Following hyperthermia, participants’ physiological responses were significantly increased after exercise. Subjects’ reaction time was significantly reduced (improved) after experiencing thermal strain and reaching hyperthermia. The cooling method had a significant impact on suppressing the physiological load, i.e., body cooling delayed the time to reach a T_c of 39 °C (p ≤ 0.05), but not cognitive inhibition and attention (reaction time and accuracy). Unexpectedly, hyperthermia resulted in shorter reaction time following exercise (16.64 ± 5.62; p < 0.03), likely influenced by increased attention/vigilance. Hyperthermia may trigger an acute increase in alertness, causing decreased reaction time.

Keywords:

• Cognitive ergonomics
• heat stress
• hyperthermia

Acknowledgments

This study was a part of Dr. Aljaroudi’s dissertation work at the University of Cincinnati Education Research Center (UC ERC) doctoral program, conducted during his fellowship at the NPPTL. The authors thank all subjects for their time and participation. The authors also thank the NPPTL Evaluation and Testing Branch for kindly permitting us to use their Environmental Chamber for this study. We thank Aitor Coca, Ph.D., Jung-Hyun Kim, Ph.D., and Tianzhou Wu, MS for their support during data collection. We also thank Lorenna Altman and Cyndy Cox from the University of Cincinnati for their technical support. We thank Raymond Roberge, MD for medical monitoring and screening during data collection.

Disclosure statement

The authors report no conflict of interest. The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of a product or use of a photo does not constitute NIOSH endorsement.

Additional information

Funding

The study was funded in part from the NIOSH ERC Grant #T42OH008432 and with NIOSH/NPPTL internal discretionary funding.