Computer prediction of human thermoregulatory and temperature responses to a wide range of environmental conditions

Abstract

A mathematical model for predicting human thermal and regulatory responses in cold, cool, neutral, warm, and hot environments has been developed and validated. The multi-segmental passive system, which models the dynamic heat transport within the body and the heat exchange between body parts and the environment, is discussed elsewhere. This paper is concerned with the development of the active system, which simulates the regulatory responses of shivering, sweating, and peripheral vasomotion of unacclimatised subjects. Following a comprehensive literature review, 26 independent experiments were selected that were designed to provoke each of these responses in different circumstances. Regression analysis revealed that skin and head core temperature affect regulatory responses in a nonlinear fashion. A further signal, i.e. the rate of change of the mean skin temperature weighted by the skin temperature error signal, was identified as governing the dynamics of thermoregulatory processes in the cold. Verification and validation work was carried out using experimental data obtained from 90 exposures covering a range of steady and transient ambient temperatures between 5 degrees C and 50 degrees C and exercise intensities between 46 W/m2 and 600 W/m2. Good general agreement with measured data was obtained for regulatory responses, internal temperatures, and the mean and local skin temperatures of unacclimatised humans for the whole spectrum of climatic conditions and for different activity levels.

UTCI-Fiala multi-node model of human heat transfer and temperature regulation

“…Fiala et al 2001), occupant comfort in buildings (Fiala et al 2003), transient indoor climate conditions in cars , asymmetric radiation scenarios and exposures to high intensity sources (Kubaha 2005, Richards and, but also anaesthesia and clinical trials. A summary is provided in Fiala et al (2010).…”

“…suppression (vasoconstriction), elevation (dilatation) of the cutaneous blood flow, shivering, and sweat moisture excretion (Fiala et al 2001 The system coefficients of the thermoregulatory system are a result of meta-regression analysis (Fiala et al, 2001) [g/min] are the overall effectors of the central nervous system, i.e. shivering, peripheral vasoconstriction and dilatation, and sweating, respectively.…”

“…The distribution coefficients for sweating and vasodilation were obtained from Stolwijk (1971). The coefficients used in the UTCI-Fiala model to distribute the overall shivering and vasoconstriction responses were estimated from simulations of cold and extreme-cold exposures (Fiala et al 2001), while the skin sensitivity coefficients were obtained from Nadel et al (1973) and Crawshaw et al (1975).…”

Opportunities and constraints of presently used thermal manikins for thermo-physiological simulation of the human body

“…The order of magnitude of the temperature gradients possible across various joints was simulated using the thermoregulation model (Fiala et al 1999;Fiala et al 2001;Psikuta et al 2012). In the model, the virtual nude average person was exposed to chosen ambient conditions for an extended period of time of up to 3h and subsequently the resultant temperature gradients across the neighbouring model compartments were determined.…”

The UTCI-clothing model

“…For use with the UTCI-Fiala model which is a multisegmental representation of the human body (Fiala et al, 1999(Fiala et al, , 2001(Fiala et al, , 2010, clothing data are required for each of the simulated body segments. For this purpose, a 'local' clothing model is developed that takes into account the non-uniformity of clothing ensembles in different temperature environments, i.e.…”