Heat Strain Assessment Under Three Different Wet Bulb Globe Temperatures With Protective Clothing

Abstract

Personal protective clothing is an important part of personal protective equipment worn by health care workers and first receivers. Wearing a vapor-barrier layer of protective clothing inhibits sweat evaporation and impairs physiological and perceptual responses. PURPOSE: To evaluate thermoregulatory responses and heat strain indices during simulated healthcare and first receivers’ tasks under three different wet bulb globe temperatures (WBGT). METHODS: Four men (25.8±6.8 yrs, 176.5±6.1 cm, 75.3±16.9 kg) wore an ensemble consisting of a loose-fitting powered air-purifying respirator, chemical resistant coverall vapor-barrier ensemble, double gloves, boots, and an apron, while performing a battery of first receiver and health care simulation activities (walking, cutting and removing clothing, scrubbing, placing a splint and cervical collar, and weight carrying) for three repetitions under three different WBGT (18, 26, and 34°C) in counterbalanced order. These environmental conditions were intended to simulate healthcare workplace conditions during mass casualty incidents. Rectal temperature (Tre) and heart rate were continuously monitored and averaged during the last 1-minute of each activity and presented as mean ± standard deviation. Physiological (PSI) and perceptual strain index (PeSI) were calculated at the end of each activity. RESULTS: Over time, Tre, PSI, and PeSI all gradually increased. At the end of the trial, Tre was significantly higher in the 34°C condition (38.5±0.4°C) than the 18°C condition (37.8±0.4°C, p=0.029) but did not differ from the 26°C conditions (38.2±0.6°C, p=0.104). The PSI was significantly higher in 34°C (6.4±1.0) than 26°C (5.1±1.2, p=0.002) and 18°C conditions (2.6±1.1, p=0.001). The PeSI was significantly higher in 34°C (7.6±1.8) than 18°C conditions (3.3±1.8, p=0.006) but did not differ between 34°C (7.6±1.8) and 26°C conditions (5.7±1.4, p=0.075). CONCLUSIONS: Tre and heat strain indices gradually increased over time across all environmental conditions. Tre and PeSI did not differ between 26°C and 34°C WBGT conditions. Tre and PeSI responses may be blunted by wearing a vapor-barrier ensemble. Future studies should examine this hypothesis to clarify the current findings.