Flow distribution in human and canine tracheobronchial airway casts

Measurements of flow rates through hollow casts of human and canine tracheobronchial airways, which extend from just below the larynx to airways 1 mm in diameter, show basic similarities in the distribution of air flow and also species differences which must be considered. The distribution of air flow, for both constant and pulsatile inspiratory flow, was measured for minute volumes equivalent to 6, 11, 17 and 22 L min-1 for the human and 3, 6, 8, and 11 L min-1 for the dog. Inertia of air flow (inertance) was found to carry more of the flow to airways of the lower lobes at higher flow rates. Basic differences in airway branching pattern result in a more distinct change in airflow distribution as flow rate changes for the canine cast as compared with the human cast. These differences should contribute to differing patterns of mass transfer of inhaled particles and gases in central airways of the two species.