Properties of lung parenchyma in distortion

Abstract

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.

Mechanical behavior of lung parenchyma as a compressible continuum: A theoretical analysis.

“…5 can also be fitted very well to the experimental data for triaxial deformation obtained by Hoppin, Lee and Dawson (1975). Lee and Frankus (1975) and Fung, Tong and Patitucci (1978) have proposed strain-energy-density functions for the experimental data presented by Hoppin, Lee and Dawson (1975).…”

“…However, we find the fit between Eq. 5 and the data of Hoppin, Lee and Dawson (1975) to be somewhat better than with their functions. Eq.…”

“…Recently, Lee and Frankus (1975) derived a strain-energy-density function of the lung parenchyma as a compressible continuum based on the experimental data of Hoppin, Lee and Dawson (1975). On the basis of this function, Liu and Lee (1978) analyzed the nonlinear, elastic finite deformations of the lung due to the action of gravitational force by the finite element method.…”

“…They obtained the large deformation solutions of the symmetric inflation of an infinitely long cylindrical hole in an infinite space by use of a numerical integration and compared the theoretic radius of the cylindrical hole with experimental measurements of the expansion of cylindrical holes drilled in the parenchyma of isolated lobes. Conceptualizing the lung parenchyma as an assemblage of many alveoli, Fung (1975) and Fung, Tong and Patitucci (1978) proposed a pseudo-strain-energy-density function based on the experimental data of Hoppin, Lee and Dawson (1975) and Vawter, Fung and West (1978), and examined the stress and strain in the lung by means of the finite element approach.…”

Towards stresses and strains in the respiratory system

“…To the authors' knowledge, no material parameters for single alveolar walls are derivable since up to now only parenchyma was tested (see for example [27], [28], [29]). Therefore we fitted the material model to experimental data published in [30] for lung tissue sheets.…”