Properties of lung parenchyma in distortion

This study offers a basis for evaluating and developing models of stress-strain behavior of the lung in distortion. Tensile forces were applied along three axes to cubes of dog lung parenchyma. With axially symmetrical force-loading, expansion was reasonably symmetrical and pressure-volume relationships were reasonably conventional in range, hysteresis, and time-dependent behavior. When the force load was changed on one axis only, that axis appeared more compliant than it did during symmetrical loading and the other axes changed length in the opposite sign. Similar distortion was apparent at the alveolar level. Data for five specimens over a range of applied loads are filed with the National Auxiliary Publications Service; graphical examples are presented herein. Relationship among the compliances for symmetrical and asymmetrical loadings were consistent with elastic theory. We derived the elastic coefficients, bulk and Young's moduli, and Poisson's ratio from the data. Poison's ratio was about 0.30 in air-filled specimens, but was lower (0.16-0.24) and increases with stress in saline-filled specimens.