Effects of surfactant on the in vivo alveolar surface-to-volume
ratio.
Miyazawa, Naoki, Shunsuke Suzuki, Tadashi Akahori, and Takao Okubo.
The First Department of Internal Medicine, Yokohama City University
School of Medicine, Yokohama 236 JAPAN
APStracts 2:0384A, 1995.
To investigate how pulmonary surfactant influences alveolar structure
in vivo, we examined the alveolar surface-to-volume (S/V) ratio of
the lung parenchyma of a live dog by light-scattering stereology
prior to and following saline lavage. We measured the back-scattered
light pattern produced by applying a laser beam to the pleural
surface of a ventilated animal and obtained the S/V ratio (equivalent
to the inverse of the optical mean free path, _). Following saline
lavage, the lung volume at transpulmonary pressure of 30 cm H2O
(defined as total lung capacity, TLC) decreased by 11.1 +/- 3.1 (SD)
% and the pressure-volume curve shifted to a lower volume. The _
-volume curve was shifted to a higher _ and to a lower volume
following saline lavage. The S/V ratio decreased following saline
lavage (_ increased by 38 +/- 27% on the deflation limb at a lung
volume of 80% of control TLC). The alveolar surface tension increased
following saline lavage and the increase in surface tension was
greater on inflation than on deflation. We conclude that depletion of
pulmonary surfactant increases the alveolar surface tension in vivo,
resulting in a decrease in the S/V ratio.
Received 21 February 1995; accepted in final form 24 August 1995.
APS Manuscript Number A203-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.