ELASTIC PROPERTIES OF LUNG PARENCHYMA - EFFECT OF PRESSURE-VOLUME HYSTERESIS ON THE BEHAVIOR OF LARGE BLOOD-VESSELS

The elastic constants of lung parenchyma were measured for states of uniform expansion. The bulk modulus was determined from small quasistatic pressure-volume (PV) perturbations, and the shear modulus was determined by indentation tests at fixed transpulmonary pressures. During full inflation-deflation PV maneuvers, both linear elastic constants were unique functions of transpulmonary pressure and were independent of the volume, which differed at the same pressure owing to PV hysteresis. Large-deformation solutions for the symmetric inflation of a cylindrical hole in the parenchyma were computed using a second-order strain-energy function for which the elastic constants were linear functions of the pressure. The solutions were used to explain changes in diameter of large intraparenchymal arteries when transpulmonary and vascular pressures were varied. Estimates of perivascular pressure (the pressure acting on the outside of intraparenchymal arteries) were obtained for both inflation and deflation limbs of the PV curve. © 1979.