Journal of Applied Physiology, Vol 68, Issue 5 2200-2207, Copyright © 1990 by American Physiological Society
Videofluoroscopic assessment of muscle fiber shortening in the in situ canine diaphragm
H. Knight, W. M. Petroll, J. M. Adams, H. A. Shaffer and D. F. Rochester
Department of Medicine, University of Virginia School of Medicine, Charlottesville 22908.
We tested the hypothesis that dynamic shortening of the costal diaphragm
can be accurately estimated from measurements of the radiographic width of
the zone of apposition (WZapp) by studying seven supine anesthetized dogs.
Both muscle fiber length, represented by the distance between implanted
radiopaque markers, and WZapp were measured from digitized recordings of
fluoroscopic images utilizing interactive computer software. The WZapp was
highly correlated with the length of costal fibers during active
respiration in all animals (mean R2 = 0.94). The accuracy in the prediction
of fiber length and shortening during breathing is enhanced by inclusion of
additional variables describing the displacement of the abdominal wall and
the resting geometric orientation of the fibers. We conclude that dynamic
fluoroscopic measurement of WZapp is a valuable technique for estimating
dynamic diaphragm fiber length and shortening. Depending on the
experimental circumstances, WZapp may be a more easily acquired indicator
of diaphragm shortening than other variables that have been previously
utilized. As such, it may provide a suitable approach to assess active
shortening of the diaphragm in humans.
