Journal of Applied Physiology, Vol 39, Issue 2 191-198, Copyright © 1975 by American Physiological Society
Simulation of regional lung emptying during slow and forced expirations
J. Pardaens, K. P. van de Woestijne and J. Clement
Regional lung emptying was simulated by means of a bialveolar lung model.
The influence of bronchial asymmetry and the vertical pleural pressure
gradient was evaluated. The model suggests that 1) in vivo the influence of
the pleural pressure gradient prevails over that of the bronchial
asymmetry; 2) in the presence of this gradient, the shape of phases III and
IV of the single-breath washout curves obtained following inspiration of a
tracer gas bolus at residual volume is determined by the recoil
pressure-volume curve of the lung, by the vertical displacements of the
alveoli, and,, at higher flow rates, by the elastic characteristics of the
airways; 3) if the pleural pressure gradient is independent of lung volume
and of flow rate, the factors mentioned in 2 suffice to produce
single-breath washout curves (phases III and IV) and regional vs. overall
lung volume relationships corresponding to those observed in vivo; 4) the
configuration of the maximal expiratory flow-volume curve is relatively
insensitive to pulmonary and bronchial asymmetry, at least in healthy
individuals.
