Journal of Applied Physiology, Vol 59, Issue 1 28-33, Copyright © 1985 by American Physiological Society
Increased gravitational stress does not alter maximum expiratory flow
D. Pyszczynski, S. N. Mink and N. R. Anthonisen
We measured maximum expiratory flow-volume (MEFV) curves in six seated
subjects during normal (+1 Gz) and increased (+2 and +3 Gz) gravitational
stress. Full MEFV curves, initiated at total lung capacity, were recorded,
as were partial MEFV curves, initiated at approximately 60% of the vital
capacity. Data were acquired in all subjects breathing air at +1 and +2 Gz;
results were available for three subjects breathing 80% He-20% O2 at +1 and
+2 Gz, and in two subjects, results were obtained at +3 Gz. Changes in
gravitational stress were not associated with changes of either full or
partial MEFV curves. The known increase in differences of regional lung
volume and recoil caused by increased gravitational stress did not
influence maximum expiratory flow. Though increased gravitational stress
probably changed regional emptying sequences little during full MEFV
maneuvers, substantial changes of emptying sequence were expected during
partial maneuvers. It is possible that such changes in emptying sequence
occurred but were not associated with changes in maximum flow because the
latter was determined by choking in central airways common to all regions.
