Human Thermoregulation Model Research Articles

A six-cylinder model of human thermoregulation for general use on personal computers.

The paper describes the basics of a six-cylinder model of human thermoregulation, written in MS-FORTRAN for use on personal computers. The heat balance equations with respect to the radial coordinate, the initial and boundary conditions, and the controller equations are explained. A complete set of parameter values is given. Emphasis is laid on the problems and status of validation. Therefore conditions and methods, on which a standard set of experimental results (dynamics of 29 core, muscle, subcutaneous and skin temperatures) is based, are explained as well as possible deficiencies both of the experimental and the simulation results. It turned out that within the environmental conditions tested (15-45 degrees C), the model, although simplifying the complex geometry of the human body to six cylinders, gives reliable results, both for steady state and dynamics of body temperature topography.

Human thermoregulation model expressing regional characteristics

Human thermoregulation model expressing regional characteristics

Closed loop control of human body temperature: results from a one-dimensional model.

A one-dimensional model of human thermo-regulation is used to solve a variety of basic problems in determining an adequate structure of the controller for metabolic heat production, skin blood flow and sweat production. Assuming one integrated central and one integrated peripheral afferent signal the controller parameters are evaluated by analysis of the control performance. Based on a validation by experimental results this allows the determination of a first optimized set of values for controller gains and weight of skin temperature feedback. Furthermore we analyse the effect of inhomogeneous distribution of heat production and blood flow, the influence of body fat content, of controller gains, of weight of skin temperature feedback and of depth of peripheral receptors on the dynamic performance. Increase of peripheral blood flow in particular evokes essentially both an increase of energy requirement in the cold and a quicker system response. Differing rates of increase of metabolic heat production are the consequence of differing body fat content. The weight of skin temperature feedback can be limited to 5...20%, because values outside this range evoke dynamic responses incompatible with the experiments. The actual value can only be determined if there is a correct assumption for the depth of the skin receptors. The use of measured superficial skin temperatures brings about an underestimation of the peripheral afferent signal. Of the controller gains it is primarily the gain of the metabolic controller which affects the dynamic response of the system. The experimental fact of a delayed onset of sweat production after a transition from cold to heat is the consequence of a high gain of the vasomotor system.

A transient model of thermoregulation in a clothed human

This paper describes a mathematical model of human thermoregulation in a clothed individual. Heat flow within and from the clothed body is expressed as a system of partial differential equations. The system is nonlinear as a result of the very nature of human thermoregulation. Such important physical properties as shivering, sweating, vasodilation and vasoconstriction are included in the simulation. Finite difference techniques are used to approximate spatial partial derivatives, thus reducing the problem to that of solving a system of nonlinear ordinary differential equations. A high accuracy approximation in the time dimension is used to generate a solution to the problem. The model is used to predict the reaction of a clothed human to various changes in environmental conditions.

The simulation of human core temperature

Two fit subjects performed two cycle-ergometer exercise bouts, one of 200 W for 48 min with a following 12-min recovery phase and one of 250 W for 30 min with a subsequent 15-min monitored recovery period. Experiments were performed in ambient conditions of 18 ± 1°C, 52% relative humidity ± 5% and 0.5 m · s −1 + 0.5 air velocity (mean ± range). Experimental values obtained from rectal and tympanic temperature sites were compared with simulation figures produced from a FORTRAN model of human thermoregulation. Data obtained provide qualified experimental support for the concept of a simple feedback model to simulate human core temperature during exercise in ambient temperatures below 20°C.

Automatic control of human thermal comfort by a liquid-cooled garment.

Astronauts utilize water cooling in a liquid-cooled garment to maintain thermal comfort during extravehicular activities (EVA's). In the Apollo and Skylab Programs, manual control of the cooling water was a necessary operation to ensure proper control of body heat storage for the EVA crewman. The development of an automatic thermal control system would be a valuable asset to the conduct of EVA, relieving the crewman of a task that can interfere with his EVA objectives. An analytical model of human thermoregulation was used to develop the equations governing the operation of such an automatic controller. A series of tests verified the feasibility of a controller utilizing only a measurement of the difference in coolant temperature into and out of the astronaut's liquid-cooled garment and an estimate of environmental heat loss to maintain the proper crewman thermal balance. Three test subjects performed over a wide range of metabolic rates, and the crewman heat balance was maintained well within allowable medical limits. This study demonstrates the use of a mathematical model to generate previously unknown physiological relationships between human thermal comfort and liquid cooled garment performance. In so doing, it quantitates physiological parameters that are difficult to relate directly by experiment. Index terms: body temperature regulation, space suit cooling, temperature control, human thermoregulation.

A two-dimensional transient mathematical model of human thermoregulation.

Current models of human thermoregulation are limited in that they fail to account for temperature distribution in any spatial direction other than radially outward from the body centerline. They are therefore incapable of accounting for nonuniform environmental conditions or nonuniform heat generation from muscles or organs within the body. However, for many situations, these nonuniform conditions are commonplace and lead to disparate skin temperatures and heat loss rates on different sides of the same body compartement. A new mathematical model of human thermoregulation that has been developed and is presented here has the capability of predicting transient temperature variations in two spatial dimensions, both radially and angularly, as measured from the body centerline. In so doing, the model accounts for nonuniform environments and internal heat generation rates. Typical results from the model are demonstrated, and comparisons with available experimental data are also presented.

Computer Simulation of Thermoregulatory Responses to Heat Stress: A Future Work Design and Training Tool

A mathematical model of human thermoregulation was developed to simulate thermoregulatory responses of man exposed to heat stress environments. The model was validated with experimental results of a man pedalling in environments of 35 and 45°C dry-bulb and 33 mm Hg water vapor pressure. The model inputs of body segment temperatures, thermal characteristics, basal blood flows, basal heat production, and of environmental and task characteristics permitted the model to be “individualized” for a specific subject, environment, and task. The model outputs of body segment temperatures, blood flows, and sweat loss at designated intervals permitted observation of the dynamic thermoregulatory responses over a 60 minute exposure period. The model was successful in predicting the change in thermal responses of a clothed man working in heat stress environments. Over the 60 minute exposure at 45°C the mean absolute difference between experimental and simulated values of head skin temperature was 0.28°C. The difference for trunk mean skin temperature was 0.12°C; for body mean skin temperature, 0.29°C; and for internal body temperature, 0.53°C.

A model of human thermoregulation during water immersion

A mathematical model for thermoregulation in humans immersed in time-varying water baths is described. The model is readily adaptable to other exposure conditions and control assumptions. Blood flow appears explicitly as a major factor in transferring heat from deep layers to the surface, and its distribution and magnitude at the surface is controlled in the model by the deviations of head core and local skin temperatures, as well as the rate of change of local skin temperature. The model results are compared with data from two water bath immersion experiments, one in which the temperature of the bath was periodically varied between 34 and 39°C, and in the other as a ramp-step function between 28 and 32°C. The resulting agreement demonstrates the feasibility of the control scheme, and also indicates ways in which distributed models of thermoregulation can be improved. The difficult inverse problem of solving the model equations for blood flow rates for a given temperature distribution is discussed, and some sample solutions are given. Extension to other exposure conditions is discussed.

Predicting effects of heat acclimatization on heart rate and rectal temperature.

Predicting effects of heat acclimatization on heart rate and rectal temperature.

Heat tolerance and acclimatization to work in the heat in relation to age.

Heat tolerance and acclimatization to work in the heat in relation to age.

Experimental determination of coefficient of heat exchanges by convection of human body.

ArticleExperimental determination of coefficient of heat exchanges by convection of human body.J Colin, and Y HoudasJ Colin, and Y HoudasPublished Online:01 Jan 1967https://doi.org/10.1152/jappl.1967.22.1.31MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByA two-part model for evaluation of thermal neutrality for sleeping peopleBuilding and Environment, Vol. 132Numerical studies on the microclimate around a sleeping person and the related thermal neutrality issues25 October 2011 | Ergonomics, Vol. 54, No. 11Convective heat transfer area of the human body25 August 2004 | European Journal of Applied Physiology, Vol. 93, No. 3The Effects of Hydration on Core Temperature in Pediatric Surgical PatientsAnesthesiology, Vol. 98, No. 4A computer model of human thermoregulation for a wide range of environmental conditions: the passive systemDusan Fiala, Kevin J. Lomas, and Martin Stohrer1 November 1999 | Journal of Applied Physiology, Vol. 87, No. 5Radiant Energy and Insensible Water Loss in the Premature Newborn Infant Nursed Under a Radiant WarmerClinics in Perinatology, Vol. 9, No. 3 More from this issue > Volume 22Issue 1January 1967Pages 31-8 https://doi.org/10.1152/jappl.1967.22.1.31PubMed6017650History Published online 1 January 1967 Published in print 1 January 1967 Metrics

Effect of acclimatization on circulatory responses to high environmental temperatures.

ARTICLESEffect of Acclimatization on Circulatory Responses to High Environmental TemperaturesC. H. WyndhamC. H. WyndhamPublished Online:01 Nov 1951https://doi.org/10.1152/jappl.1951.4.5.383MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByExercise heat acclimation has minimal effects on left ventricular volumes, function and systemic hemodynamics in euhydrated and dehydrated trained humansGavin Travers, José González-Alonso, Nathan Riding, David Nichols, Anthony Shaw, and Julien D. Périard15 October 2020 | American Journal of Physiology-Heart and Circulatory Physiology, Vol. 319, No. 5Cutaneous vasomotor adaptation following repeated, isothermal heat exposures: evidence of adaptation specificityApplied Physiology, Nutrition, and Metabolism, Vol. 43, No. 4Individualized model of human thermoregulation for the simulation of heat stress responseGeorge Havenith1 May 2001 | Journal of Applied Physiology, Vol. 90, No. 5MEDICAL RESEARCH COUNCIL CLIMATE AND WORKING EFFICIENCY RESEARCH UNIT31 May 2007 | Ergonomics, Vol. 1, No. 3 More from this issue > Volume 4Issue 5November 1951Pages 383-395 https://doi.org/10.1152/jappl.1951.4.5.383PubMed14938269History Published online 1 November 1951 Published in print 1 November 1951 Metrics