Journal of Applied Physiology, Vol 45, Issue 6 903-907, Copyright © 1978 by American Physiological Society
Is inert gas washout from the tissues limited by diffusion?
Y. Ohta, S. H. Song, A. C. Groom and L. E. Farhi
To determine the extent to which diffusion may limit the exchange of gases
stored in the tissues, nine dogs were allowed to breathe an O2-N2-Ar
mixture until saturation was achieved; the inspired gas was then changed to
one containing neither N2 nor Ar, and the level of these two species in the
arterial and in the mixed venous blood was monitored during the washout. A
theoretical analysis shows that in a situation where peripheral gas
transport is limited entirely by perfusion, the washout curves should be
identical, provided concentrations are expressed as a fraction of the
initial value. When the process is restricted by diffusion through the
tissues, Ar is expected to lag because of its higher molecular weight. In
all animals, the rate of elimination of the two tracers was the same,
indicating that the time course of storage or release of inert gas from
body stores is governed (mainly or entirely) by perfusion.
