Computational model of oscillatory airflow in a bronchial bifurcation.

Airflow distribution in the bronchial tree is an important factor that controls gas mixing in the lungs, especially, in diseased lungs or during high frequency ventilation. A nonlinear analog model has been developed to investigate the dependency of airflow distribution in asymmetric bronchial bifurcations on structural and physiological parameters. The system parameters (electrical analogs) are time-dependent and were extracted from laboratory studies of airway models and physiological measurements. The model was used to study flow distribution in peripheral pathways of normal and pathological airways during different modes of quiet breathing as well as high frequency ventilation. Model simulations revealed that (i) increasing of ventilation frequency or stroke volume increases the time and percentage of pendelluft in each cycle, (ii) diameter asymmetry between parallel pathways is more dominant than length asymmetry and enhances the degree of asynchronous ventilation to peripheral pathways, and (iii) asymmetry in the compliance of peripheral airways and lung parenchyma greatly increases the degree of asynchronous ventilation.