Specific ventilation distribution in microgravity.
Verbanck, Sylvia, Dag Linnarsson, G. Kim Prisk, and Manuel Paiva.
Akademisch Ziekenhuis, Vrije Universiteit Brussel, Brussels,
Belgium; Department of Physiology, Karolinska Institute, Stockholm,
Sweden; Department of Medicine, University of California San Diego,
La Jolla, California; Biomedical Physics Laboratory,
Universit[acute]e Libre de Bruxelles, Brussels, Belgium
APStracts 2:0543A, 1995.
We studied the contribution of inter- and intraregional inhomogeneity
of specific ventilation (_V/Vo) from the rebreathing inert gas trace
in microgravity ([mu]G) and on ground (1 G). The rebreathing tests
were carried out by four astronauts before, during and after the 9
-day Spacelab D-2 mission. Starting from functional residual capacity,
the rebreathing maneuver consisted of eight reinspirations from a bag
filled with 1.8 to 2.2L of test gas mixtures containing approximately
5% Argon. The rate of Argon equilibration in the rebreathing bag was
quantified by determining the logarithm of the actual minus
equilibrated Argon concentration normalized to inspired minus
equilibrated Argon concentration, termed RBeq. A compartmental model
of the lung (J. Appl. Physiol. 76:445-454, 1994) was used to validate
the method for determining RBeq, and to simulate the influence of
intra- and interregional _V/Vo inhomogeneity on the RBeq curve. The
comparison between the experimental 1 G and [mu]G RBeq curves and
model simulations shows that gravity-independent _V/Vo inhomogeneity
is at least as large as gravity-dependent _V/Vo inhomogeneity.
Received 17 July 1995; accepted in final form 1 December 1995.
APS Manuscript Number A776-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 12 December 95