Subjective estimates of physiological responses and perceptual-motor performance in the heat

Heat stress associated with aerosol PPE and its impact

BACKGROUND

Aerosol personal protective equipment (PPE) is subjectively reported to negatively impact healthcare workers' performance and well-being, but this has not been assessed objectively.

AIMS

This randomized controlled crossover study aimed to quantify the heat stress associated with aerosol PPE and to investigate its impact upon mood, cognitive and motor function, and task performance.

METHODS

Sixteen healthy, young, lean participants (eight males) undertook an exercise protocol, which simulated the metabolic expenditure of hospital work: once wearing aerosol PPE (PPE visit) and once wearing standard surgical attire (control visit). Participants walked on a treadmill for 2 h followed by 30-min rest. Core temperature, heart rate, urine specific gravity, weight, grip strength, mood (Bond-Lader scale) and task performance (Intubation of a Manikin) were recorded. Values are between-visit mean (standard deviation) differences.

RESULTS

On the PPE visit core temperature (+0.2 (0.3)°C; P < 0.01), heart rate (+12 (13) bpm; P < 0.001), urine specific gravity (+0.003 (0.005); P < 0.05) and intubation task time (+50 (81) s; P < 0.01) were greater than on the control visit; and alertness (-14 (21) mm; P < 0.001), contentment (-14 (15) mm; P < 0.001) and grip strength (-4 (4) N; P < 0.01) were less.

CONCLUSIONS

This study demonstrates that wearing aerosol PPE in a simulated hospital environment results in heat exhaustion and has a negative impact upon mood, motor function, and task performance. Whilst wearing PPE is important to prevent disease transmission, strategies should be developed to limit its impact upon healthcare workers' performance and well-being.

Comparison between male and female subjective estimates of thermal effects and sensations

Thirty-one male subjects aged between 18 and 40 years and 15 female subjects aged between 18 and 24 years were used to compare male and female subjective estimates of the effect of heat on thermal sensation, drowsiness, boredom and fatigue. The subjects were exposed to climatic conditions between 74 degrees and 110 degrees F (23.3 degrees and 43.3 degrees C) Wet Bulb Globe Temperature (WBGT) while performing perceptual-motor tasks. Linear regression equations relating thermal sensation and ambient temperature were developed. These equations showed that the preferred temperature for males (71.6 degrees F (22 degrees C) WBGT) is significantly lower than that for females (77.1 degrees F (25 degrees C) WBGT). Females tend to feel more uncomfortable than males at both high and low temperature extremes. The subjective responses of thermal sensation take the same pattern as the subjective estimates of physiological responses to heat. Subjective estimates of thermal sensation in the heat relate directly to actual changes occurring in body temperature and heart rate. The subjective estimates by both males and females of drowsiness, boredom and fatigue form inverted U-curves when plotted against increasing temperature. The peaks of the inverted U or arousal curves for the two groups occur at 90 degrees F (32.2 degrees C) WBGT. The females reported higher levels of both drowsiness and boredom than the males at all temperatures, and the males reported higher fatigue than the females at the upper temperature levels.