Influence of lung parenchyma on collapsibility of dog bronchi

In five excised dog lobes in the distended state, we inserted several small beads into the bronchi roughly at their third branches and glued them airtight to the bronchial wall with adhesive substance, except for one which was open and through which the entire lobe could be expanded via collateral channels. This permitted us to measure the volume-pressure behavior of bronchi at different fixed lung tensions. From differences in pressure-volume curves of both the bronchi in situ and the bronchi intact within the lung showed a remarkably greater resistance to collapsing that dissected bronchi, and this characteristic tended to be much more intense when lung tension was increased. Determinants of maximum expiratory flow were discussed with these findings.