Journal of Applied Physiology, Vol 47, Issue 1 228-232, Copyright © 1979 by American Physiological Society
Effect of inhalate thermal conductivity and high O2 in producing hypothermia
A. V. Beran, R. A. Shinto, K. G. Proctor and D. R. Sperling
The effect of an increase in inhalate thermal conductivity and the fraction
of inspiratory O2 (FIO2) on the rate of cooling and rewarming using a
surface-inhalate heat exchange method was evaluated. Male New Zealand White
rabbits were divided into three groups: those ventilated with air, those
with 20% O2 + 80% He, and those with 100% O2. All animals were cooled to an
esophageal temperature of 22.5 degrees C (or for 180 min maximum).
Following a 15-min exposure to room air, the animals were connected to the
humidifying and warming system. He-O2 had the highest thermal conductivity
and the animals ventilated with it had the fastest cooling rate. One
hundred percent O2 and room air had similar thermal conductivities, but the
animals ventilated with 100% O2 had significantly lower cooling rates.
These data indicate that, while maintaining a constant surface heart
exchange, the rate of heat exchange across the lung can be modified by
altering the thermal conductivity of the inhalate gas mixture. Total heat
exchange can also be modified by hyperoxemia-induced hemodynamic changes.
