Heart rate variability assessment during work in personal protective equipment under environmental thermal load

Abstract

Introduction. When performing work in open areas in the summer, electrical engineering personnel use shunt shielding kits to protect against industrial frequency electric fields. However, the use of personal protective equipment has an additional thermal load on the human body, which is assessed, among other things, by changes in the indicators of the functional state of the cardiovascular system. The study aims to assess the variability of the heart rate when working in shunting screening kits under conditions of modeling the thermal load of the environment. Materials and methods. The study carried out in seven volunteers using power frequency electric field personal protective equipment. Heart rate variability assessed for simulated elevated thermal load environment. The volunteers worked with physical activity (walking) of 60 minutes treadmill and 15 minutes rest in the same climatic conditions (recovery period) after. Temperature and humidity inside shunting shielding personal suit recorded. The determination and statistical analysis of heart rate variability based in electrocardiogram were performed. Based on the recording of an electrocardiogram, the authors carried out the determination and statistical analysis of heart rate variability indicators. Results. Volunteers heart rate variability analysis showed that stress index median values during work and recovery periods were 345 cu and 96 cu without shunting shielding personal suit. Work in shunting shielding personal suit showed that stress index median values were 196 cu and in recovery period 152 cu. RR-interval median values under work in personal protective equipment were lower (0.552 s) than without personal protective equipment (0.617 s). The results revealed the tendency to body thermoregulatory mechanisms strain increase in work time, characterized by RR-intervals differences with personal protective equipment use and without (ΔRR) — 0.057 s, and organism partial recovery during rest time (ΔRR — 0.113 s) with personal protective equipment. Limitations. The number of volunteers was due to the limited duration of the study. Conclusion. The results of cardiovascular system functional state assessment by heart rate variability indicate stress with regulatory systems overstrain with and without personal protective equipment. Power frequency electric field personal protective equipment makes additional external thermal load to human body as stress index (196 cu), RR-intervals (0.552 s) in work period and slight decrease in recovery period (152 cu and 0.566 s). Stress index high values in the recovery period associated with prolonged environment thermal load exposure due to climatic parameters and volunteers staying in PPE after the end of physical work. Ethics. The Local Ethics Committee of the Izmerov Research Institute of Occupational Health approved this study carried out under the WMA Declaration of Helsinki (record № 3 from 23.03.2022).