Publication Abstracts

ASEM V67N6: A Miniswine Model of Acute Exertional Heat Exhaustion.

Gentile BJ, Szlyk-Modrow PC, Durkot MJ, Krestel BA, Sils IV, Tartarini KA, Alkhyyat AM.
Aviat Space Environ Med 1996; 67:560-7

Abstract

Method: We examined the thermoregulatory and hemodynamic responses of 12 miniswine (31 +- 3.9 kg) during 25 - 30 min of treadmill exercise (5.4 km h-1, 5% grade) under cool (10°C), moderate (20°C) and warm (30°C) ambient temperature (Ta) conditions. Results: Within 15 - 20 min of exercise at Ta = 30°C, the miniswine demonstrated significant hyperventilation, hypersalivation, and unsteady gait. Exercise-heat endurance time (7) at Ta = 30°C decreased by 35% and 40% in comparison to T at Ta = 20°C and 10°C, respectively. This resulted from a significant rise in heat strain (5)-defined as the rate of change in rectal temperature. Averaged throughout exercise, 5 increased from 0.04 +- 0.01 °C min ^-1 and 0.05 +-0.02 °C min ^-1 at Ta = 10°C and 20°C, respectively, to 0.10 +- 0.03 °C min^-1 at Ta = 30°C. Due to the comparatively large storage capacity of the porcine spleen relative to humans, splenectomized miniswine were used. This permitted calculation of percentage changes in plasma volume (% PVc) from hematocrit (HTC) and hemoglobin (HGB) without the confounding effects of splenic red cells released into the circulation during exercise. Independent of To, pre exercise PVc decreased 3%-5% (p 0.05) within the first 10 min of exercise, but increased 5% - 9% (p 0.05) by 10 min post-exercise. Conclusion: We conclude that the poor thermoregulatory ability of miniswine manifested in insignificant sweating and restricted evaporative cooling, may make them an appropriate model for acute exertional heat exhaustion in humans working in hot, humid conditions and/or wearing impermeable protective clothing. Further evaluation of plasma volume changes from HCT and MGB in a miniswine model should consider the merit of a splenectomized design.

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Table of Contents for Volume 67, Number 6 of the ASEM journal.