Vol. 94, Issue 1, 75-82, January 2003
Tidal volume single-breath washin of SF6 and
CH4 in transient microgravity
Brigitte
Dutrieue1,
Manuel
Paiva1,
Sylvia
Verbanck2,
Marine
Le Gouic3,
Chantal
Darquenne4, and
G. Kim
Prisk4
1 Biomedical Physics Laboratory, Université
Libre de Bruxelles, 1070; 2 Department of Pneumology,
Akademisch Ziekenhuis, Vrije Universiteit Brussels, 1090 Brussels,
Belgium; 3 European Space Agency, ESTEC,
NL-2200 AG Noordwijk, Holland; and
4 Department of Medicine, University of California,
San Diego, La Jolla, California 92093-0931
We performed tidal volume
single-breath washins (SBW) by using tracers of different diffusivity
and varied the time spent in microgravity (µG) before the start of
the tests to look for time-dependent effects. SF6 and
CH4 phase III slopes decreased by 35 and 26%,
respectively, in µG compared with 1 G (P < 0.05), and the slope difference between gases disappeared. There was no
effect of time in µG, suggesting that neither the hypergravity period
preceding µG nor the time spent in µG affected gas mixing at
volumes near functional residual capacity. In previous studies using
SF6 and He (Lauzon A-M, Prisk GK, Elliott AR, Verbanck S, Paiva M, and West JB. J Appl Physiol 82: 859-865,
1997), the vital capacity SBW showed an increase in slope difference
between gases in transient µG, the opposite of the decrease in
sustained µG. In contrast, tidal volume SBW showed a decrease in
slope difference in both µG conditions. Because it is only the
behavior of the more diffusive gas that differed between maneuvers and
µG conditions, we speculate that, in the previous vital capacity SBW,
the hypergravity period preceding the test in transient µG provoked
conformational changes at low lung volumes near the acinar entrance.
vital capacity single-breath washout; phase III slope; helium; gas
mixing; sustained microgravity
