Distortion of submerged dog lung lobes

The conically shaped caudal lobes of dog lungs were submerged, tip downward in saline, and the lateral surfaces of the lobes were thereby exposed to a hydrostatic gradient in transpulmonary pressure. The force that was required to balance the buoyancy was applied through a clip attached to the tip of the lobe. The locations of metal markers implanted in the parenchyma and attached to the surface were tracked, and regional volume and the horizontal and vertical components of strain were obtained as functions of vertical position. An engineering analysis of the deformation is qualitatively consistent with the data, but the predicted strains are larger than the observed strains. From the experimental and analytical results, we conclude that, for this deformation, the regional volume-local transpulmonary pressure curve closely follows the pressure-volume curve because negative horizontal strains nearly balance the positive vertical strain caused by the buoyancy force.