Small distortion properties of lung parenchyma as a compressible continuum

Volume dependent mechanical properties of lung parenchyma are derived from a homogeneous, compressible, initially isotropic elastic model subjected to small distortion superimposed on large deformation. The model is based on experimental data for excised dog lungs. General linear constitutive equations are derived for each finite intermediate state of stress. Constraints needed for the deduction of a strain energy function of the parenchyma as a compressible continuum are considered. Properties are defined for each isotropic intermediate state of stress. These are given in terms of physical constants which provide the basis for modeling a variety of problems in lung elasticity. An example of such a problem is illustrated.