A modified Kalman filter-based model for core temperature estimation during exercise and recovery with/without personal cooling interventions

Abstract

One of the most important parameters to consider while analysing heat related illness is the human body core temperature. It is therefore required to monitor real-time core temperature in an ambulatory situation for industrial workers, athletes, military personnel, and a variety of other people. As conventional methods of monitoring core temperature are unsuitable for ambulatory use or prohibitively expensive, it is necessary to develop a reliable, inexpensive and non-invasive method for real-time measurement of core temperature. Kalman filter based models for core temperature estimation are found promising to meet these requirements. In this work, we have highlighted one of the major shortcomings of the existing extended Kalman filter model and proposed a modification. The modified extended Kalman filter based model has better performance compared to the existing model in estimating the core temperature as it considers two separate measurement models for exercise and recovery periods. The proposed modified model is validated using human trials data which includes participants wearing regular clothing and different types of personal cooling clothing. It is found that the proposed modified model can predict core temperature more accurately (bias= -0.03 to -0.06°C, LoA=±0.14 - ±0.32°C, and RMSE=0.09-0.16°C) as compared to the existing model (bias=-0.03 - 0.08°C, LoA=±0.26 - ±0.33°C, and RMSE=0.14°C-0.18°C). Personal cooling intervention minimises core temperature rise significantly and thus helps in heat stress mitigation. It is observed that the proposed modified model can estimate core temperature more accurately for cooling intervention cases and intermittent working cases as compared to the existing model. It can be used effectively in an ambulatory setting, but for situations where higher accuracy is required and invasiveness of the method is not a concern, direct contact method of core temperature is always preferred as the proposed model has varying accuracy levels between individuals.

Keywords: Core temperature estimation; Extended Kalman filter; Kalman filter; Non-invasive method; Personal cooling clothing; Real-time monitoring.