Collateral resistance at alveolar level in excised dog lungs

In excised dog lungs, collateral resistance was measured among separate groups of alveoli. Alveoli beneath the pleural surface were multipunctured by a small needle, and alveolar pressure and flow were measured in capsules glued onto the punctured pleural surface. When the airway opening was closed, collateral ventilation appeared to occur mainly through the regular airway system, but not through the collateral channels. When the airway opening and the segmental bronchus were occluded, collateral airflow appeared to occur first, within the segment through its airway system; second, through the intersegmental collateral channels to other segments; and third, to output alveoli through the airway system. When the airway was obstructed down to the bronchilar level with silicone rubber, collateral resistance became extremely high. It was concluded that collateral resistantce at the alveolar level was considerably higher than the resistance in the regular airway system.