Evaluation of the physiological changes in prehospital health‐care providers influenced by environmental factors in the summer of 2020 during the COVID‐19 pandemic

AIM: Wearing personal protective equipment (PPE) is essential to prevent infection transmission, but the risk of heatstroke increases with wearing PPE in a humid and hot environment. Therefore, we aimed to examine how environmental parameters change the body physiology in a hot environment during the coronavirus disease (COVID‐19) pandemic. METHODS: This was a retrospective cohort study extracted from the MEDIC Japan heatstroke prevention database, which was recorded between 1 August and 7 September, 2020. Its database is a registry collection from seven healthy health‐care providers. Subjects recorded their own vital signs (forehead and tympanic temperature, blood pressure, pulse rate, and oxygen saturation) and environmental factors (type of weather, wet‐bulb globe temperature [WBGT], air temperature, humidity, and location) every hour during their working shift. RESULTS: From 323 records, a weak positive but statistically significant correlation was observed between WBGT and pulse rate (correlation coefficient [95% confidence interval], r = 0.34 [0.23, 0.45]) and between WBGT and core body temperature. Forehead temperature had a stronger correlation than tympanic temperature (forehead, r = 0.33 [0.21, 0.43]; tympanic, r = 0.17 [0.05, 0.28]), which also showed a larger effect (forehead, η(2) = 0.08; tympanic, η(2) = 0.05). The effect size of oxygen saturation measured outdoors was large (η(2) = 0.30). Forehead temperature increased abruptly at 28°C WBGT and at 33°C air temperature. CONCLUSION: A hot environment significantly affected forehead temperature, and the daytime imposed a high risk of heatstroke. To avoid heatstroke, environmental parameters are important to note as outdoor environments had a large effect on vital sign changes depending on the time of day.