Journal of Applied Physiology, Vol 75, Issue 4 1624-1629, Copyright © 1993 by American Physiological Society
Dynamic behavior of alveolar surface-to-volume ratio in live dogs by light-scattering stereology
T. Akahori, S. Suzuki, M. Suzuki and T. Okubo
First Department of Internal Medicine, Yokohama City University School of Medicine, Japan.
To investigate the behavior of the surface-to-volume ratio (S/V) in lung
lobes of live dogs, we measured the backscattered light pattern produced by
applying a laser beam to the pleural surface. This pattern was used to
estimate the optical mean free path, which is approximately proportional to
the inverse square of the geometric S/V. Measurements were performed in
mechanically ventilated animals with the chest widely opened. We found that
during quasi-static large volume excursion, S/V changed approximately as
the one-third power of lung volume but with hysteresis such that S/V during
deflation was higher than during inflation. This finding is consistent with
a relatively large stress hysteresis of surface tension compared with that
of the tissue. During tidal breathing, however, the geometric hysteresis
was inconsistent among animals at low frequency but was consistently
changed at higher frequencies in a direction suggesting a lesser role of
surface tension relative to tissue stress hysteresis.
