Abstract
With increasing heat-wave frequency, the prevention and public awareness of heat-related illnesses has become an essential topic. In the standard for heat strain and stress, empirical guidelines to prevent excess core temperature rise above 1 °C have been prescribed for workers. However, measuring core temperature change in our daily life or working place is not straightforward. The estimation of core temperature from measured vital signals in a non-invasive manner is thus essential for the management of heat stress or strain. Here, we propose an estimation method for core temperature change by a simplified thermodynamics model with the measured heart rate and ambient conditions (temperature and relative humidity). Our proposed model is based on a two-layer two-compartment model with tuned parameters, which were derived from comparison between the computations using high-resolution anatomical human body model. Our model exhibited good agreement with the measured core temperature rise; the computed and measured core temperature rise for the naked trial were 0.54 °C and 0.53 °C, whereas those for the clothed trial were 0.70 °C, and 0.71 °C, respectively. Furthermore, our compartment model with vital data measured from a wearable device achieved good estimation in real time for field measurement in addition to computational replication with a previous study.
Highlights
The number of heat wave cases has been increasing in most areas of the world [1, 2]
The range of temperature was chosen as 32–38 oC, and the relative humidity was set to 50 %
The core temperature defined in Eq (6) was used in the compartment model, whereas the arterial blood temperature was used in the anatomical model, which may have had a retarded effect in the order of several minutes
Summary
The number of heat wave cases has been increasing in most areas of the world [1, 2]. With increasing frequency of extreme heat waves, morbidity of heat-related illnesses has been increased [3]. It has remained high at 71,317 in 2019 and 64,869 in 2020 [5] Several indexes, such as the heat index [6], wet-bulb globe temperature (WBGT) [7], and the universal thermal climate index [8], are used to estimate the heat stress and strain as well as thermal comfort [9, 10]. These indexes are metrics of heat-related risks assuming that an individual remains in the same environmental condition; their daily maximum values or instantaneous values, such as when workers start to work, are often used. Environment changes with time, and the duration of heat exposure is case-specific
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