Journal of Applied Physiology, Vol 65, Issue 4 1757-1765, Copyright © 1988 by American Physiological Society
Inhomogeneity during deflation of excised canine lungs. I. Alveolar pressures
D. O. Warner, R. E. Hyatt and K. Rehder
Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota 55905.
Factors both intrinsic and extrinsic to the lung may cause inhomogeneity of
alveolar pressures during deflation. Wilson et al. (J. Appl. Physiol. 59:
1924-1928, 1985) predicted that any such inhomogeneity would be limited by
interdependence of regional expiratory flows. To test this hypothesis and
to explore how the pleural pressure gradient might affect inhomogeneity of
alveolar pressures, we deflated at submaximal flows excised canine lobes
that first were suspended in air and then were immersed in foams that
simulated the vertical gradient of pleural pressure. Interregional
inhomogeneity of regional transpulmonary pressures was measured with use of
an alveolar capsule technique. Flow-dependent inhomogeneity of alveolar
pressures was present, with differences in alveolar pressure quickly
relaxing to a constant limiting value at each flow. Foam immersion
increased inhomogeneity at a given flow. We conclude that factors intrinsic
to the lung cause significant inhomogeneity of alveolar pressures at
submaximal expiratory flows and that this inhomogeneity is enhanced by the
extrinsic gradient of pleural pressure. These observations are consistent
with the interdependence of flow proposed by Wilson et al.
