Poster L26 - A Mathematical Model of Cold-induced Vasodilation in the Human

Introduction: Cold-related injuries pose a health threat to Warfighters and an impediment to Force Readiness during extended operations in cold-weather environments [1]. The cold-induced vasodilation [2] (CIVD) response of the human body to Arctic-like environments helps delay or prevent cold injuries to peripheral regions, such as the hands and feet. To more comprehensively predict the thermal responses of these peripheral regions to cold stress, here we extended our previously developed and validated anatomically accurate three-dimensional (3-D) whole-body thermoregulatory human [3] by incorporating a new phenomenological formulation of the CIVD mechanism.

Materials and

Methods: The 3-D whole-body human thermoregulatory model represents a 50th percentile U.S. male, comprised of 29 metabolically active organs and biological tissues, and accounts for heat-transfer mechanisms within the human body, thermal interaction of the human body with the environment, and thermoregulatory mechanisms that regulate the thermal state of the body. In this model, using the modified Pennes bioheat equation [3], we solved the macroscopic energy balance for the time-dependent temperature. In addition, we modulated the cyclic vasodilation and vasoconstriction flow of warm blood due to CIVD from the body core to the peripheral regions solely by determining the heat transfer exchange between the skin and the surrounding environment. We defined the thermal state of CIVD based on the value of the fingertip/toe-tip skin temperature, and deactivated it when the core body temperature decreased to 36.5 °C (Figure 1, left panel). We calibrated and validated the extended model using eight distinct studies involving 153 unique male subjects exposed to 10 experimental conditions, including cold-air exposure of the whole body as well as air exposure and cold-water immersion of the hand or foot.

Results, Conclusions, and Discussions: Results and

Discussion: With CIVD incorporated, the model predictions yielded root mean square errors (RMSEs) of < 3.0 °C for skin temperature, which represented a reduction of up to 3.6 °C compared to when we did not consider CIVD (Figure 1, right panel). Similarly, the incorporation of CIVD increased the fraction of predictions within two standard errors of the measured data by up to 63%. The model predictions yielded RMSEs for core body temperature of < 0.2 °C.

Conclusions: We validated our extended whole-body model with CIVD by comparing predicted skin (hand, finger, and toe) temperature with experimental data collected during cold-air exposure or cold-water immersion. The model can be used to provide guidelines to reduce the risk of cold-related injuries.

References:
1. Armed Forces Health Surveillance Division, Medical Surveillance Monthly Report 29 (2022).
2. Lewis, Heart, 15 (1930):177-208.
3. Gulati et al., J. Appl. Physiol., 133(2022):288-310.

Acknowledgements (Optional): Acknowledgements: This research was supported by the Military Operational Medicine and the Combat Casualty Care Program Area Directorates of the United States Army Medical Research and Development Command (USAMRDC). The Henry M. Jackson Foundation was supported by the USAMRDC under Contract No. W81XWH20C0031.

Disclaimer: The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the United States Army, the United States Department of Defense, or The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. This abstract has been approved for public release with unlimited distribution.