Uncompensable Heat Stress Improves Manual Dexterity, But Does Not Affect Risk Propensity

Abstract

PURPOSE: Healthcare workers in the West African Ebola Treatment Units experienced substantial heat stress from wearing personal protective equipment (PPE) while performing light activities in a hot environment. It is unknown if uncompensable heat stress alters risk propensity or manual dexterity, which could impact the health of the worker and/or patient. We tested the hypothesis that uncompensable heat stress increases risk-taking propensity and impairs manual dexterity. METHODS: Fifteen healthy subjects (2 women) aged 22 ± 2 y completed a single experimental trial in 40°C and 60% relative humidity while wearing a hooded Tyvek chemical resistant coverall, an N95 respirator mask, goggles, gloves, boots, and an autopsy apron. Subjects walked on the treadmill for 30 min at 60% of their age predicted maximal heart rate, which was followed by 15 min seated rest. This cycle was repeated until: participants reached 120 min, the subject terminated the test, or their physiological measures exceeded safe parameters. Subjects completed the Balloon Analogue Risk Task (BART) and two dexterity tasks (Tool Dexterity and Minnesota Manual Dexterity) pre and post the exercise while in the hot environment. RESULTS: Core temperature (1.8 ± 0.6°C; p<0.01), mean skin temperature (3.8 ± 0.7°C; p<0.01), and heart rate (55 ± 21 bpm; p<0.01) increased during exercise, while body mass decreased (1.1 ± 0.4%; p<0.01). Core-to-skin temperature gradient decreased from pre to post (1.1 ± 0.02°C vs. 1.0 ± 0.02°C; p<0.01) During exercise, perceived exertion (p<0.01), thermal sensation (p<0.01), thermal comfort (p<0.01), sweating sensation (p<0.01), and dyspnea (p<0.01) ratings increased. There was no change in the number of balloon explosions on the BART, an objective measure of risk propensity, from pre to post (p=0.43). Time to complete the Tool Dexterity task did not differ between pre and post (p=0.49). Time to complete the Minnesota Manual Dexterity task decreased from pre to post for both placing (270.4 ± 29.6 s vs. 252.0 ± 27.7 s; p=0.03) and turning (230.2 ± 25.7 s vs. 204.9 ± 33.3 s; p<0.01). CONCLUSION: Despite considerable thermal strain, light exertion in the heat while wearing encapsulating healthcare PPE did not alter risk propensity, but improved aspects of manual dexterity.