Lumped versus distributed thermoregulatory control: results from a three-dimensional dynamic model.

Area of Science:

• Physiology
• Biophysics
• Computational Biology

Background:

• Human thermoregulation involves complex physiological responses to thermal challenges.
• Accurate modeling requires integrating heat transfer principles with physiological data.
• Previous models often simplified the spatial aspects of thermal regulation.

Purpose of the Study:

• To develop and validate a detailed 3D model of the human thermal system.
• To evaluate different control equations for metabolic heat production, blood flow, and sweat production.
• To determine the necessity of spatial distribution in thermoregulatory control models.

Main Methods:

• Utilized a 3D spatial grid model (0.5-1.0 cm resolution) based on physical heat-transfer equations.
• Assigned 54 distinct physical parameter values to different body areas/organs.
• Solved equations using a modified alternating direction implicit method for simulation.

Main Results:

• Identified simplest closed-loop control equations compatible with experimental data.
• Demonstrated the essential role of spatial distribution for heat production and blood flow control.
• Found distributed controller gains necessary for shivering control, distinct from muscle distribution.

Conclusions:

• Spatial distribution is critical for accurate simulation of thermoregulation, especially for shivering.
• Lumped parameter control may be adequate for simulating sweat response to homogeneous heat loads.
• The validated 3D model can analyze thermoregulatory mechanisms and inform clinical/environmental health applications.