Journal of Applied Physiology, Vol 65, Issue 4 1693-1702, Copyright © 1988 by American Physiological Society
Bronchial distribution of gas mixing in a model of the upper and central airways
A. F. Simone, J. S. Ultman and A. B. Jebria
Department of Chemical Engineering, Pennsylvania State University, University Park 16802.
Longitudinal mixing of He, O2, and sulfur hexafluoride boluses with air
flowing through a three-generation tracheobronchial airway model was
evaluated as the increase in volume variance of gas concentration
distributions monitored at upstream and downstream sampling ports. Mixing
was partitioned between tracheal and branched regions of the model at
steady inspiratory and expiratory airflows from 0.044 to 0.884 l/s, both in
the absence and in the presence of a removable larynx cast. During
inspiration in the absence of the larynx, mixing increased as airflow
increased, reaching a peak value at 0.2 l/s, and decreasing as airflow
increased further. This mixing peak was higher in the branched region than
in the tracheal region and was inversely related to the diffusion
coefficient of the indicator gas-air mixture. During inspiration in the
presence of the larynx, a mixing peak was observed in the tracheal region,
but mixing peaks in the branched region were eliminated by turbulence
propagated downstream from the larynx. During expiration, laryngeal
turbulence was propagated far enough downstream (i.e., proximal to the
trachea) that mixing peaks could be observed in both tracheal and branched
regions whether or not the larynx cast was present.
