Tracheal gas exchange: perfusion-related differences in inert gas
elimination.
Souders, Jennifer E., Steven C. George, Nayak L. Polissar, Erik R.
Swenson, Michael P. Hlastala.
Departments of Anesthesiology, Chemical Engineering, Biostatistics,
Medicine, and Physiology and Biophysics, University of Washington,
Seattle, Washington
APStracts 2:0148A, 1995.
Exchange of inert gases across the conducting airways has been
demonstrated using an isolated dog trachea preparation and has been
characterized using a mathematical model (Swenson et.al., J. Appl.
Physiol., 72(4): 1581-1588, 1992). Theory predicts that gas exchange
is both diffusion- and perfusion-dependent, with gases of higher
blood-gas solubility ([lambda]b) exchanging more efficiently. The
present study evaluated the perfusion-dependence of airway gas
exchange in an in vivo canine tracheal preparation. Eight dogs were
studied under general anesthesia using the same isolated tracheal
preparation. Tracheal perfusion () was altered from control (o) by
epinephrine or papaverine instilled into the trachea and was measured
using fluorescent microspheres. Six inert gases of differing
[lambda]b were used to measure inert gas elimination. Gas exchange
was quantified as excretion (E), equal to exhaled partial pressure
(PE) divided by arterial partial pressure (Pa). Data were plotted as
ln [E/(1-E)] vs. ln/o and the slopes determined by least squares.
Excretion was a positive function of , and the magnitude of the
response of each gas to changes in was similar and highly significant
(P < 0.0002). These results confirm a substantial perfusion
-dependence of airway gas exchange.
Received 1 July 1994; accepted in final form 29 March 1995.
APS Manuscript Number A656-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.