Pleural pressure with lobar obstruction in dogs.

The effects of acute lobar obstruction on pleural surface pressure in supine dogs were examined. The right lower lobes (RLL) were obstructed at FRC in some dogs while in others the left lung and RLL were both obstructed at FRC. At the end of the subsequent inspiration, costal surface pressure was less over the obstructed lobe than over the unobstructed right upper lobe. Alveolar pressure within the obstructed RLL decreased relative to tracheal pressure at end inspiration resulting in an inflating pressure being applied to the obstructed lobe. In most dogs elastic recoil increased at the lateral costal margin of the obstructed RLL implying the application of a deforming pressure to the obstructed lobes. The tendency to inflate and deform the obstructed RLL was greater during spontaneous breathing than during artificial ventilation.