Poro-Visco-Elastic Modeling of Mechanical Wave Motion in the Lungs

Noninvasive measurement of mechanical wave motion (sound and vibration) in the lungs may be of diagnostic value, as it can provide information about the mechanical properties of the lungs, which in turn are affected by disease and injury. In this study, two theoretical models of the vibro-acoustic behavior of the lung parenchyma are compared: (1) a Biot theory of poroviscoelasticity and (2) a simplified “bubble swarm” model for compression wave behavior. A “slow” compression wave speed predicted by the Biot theory formulation agrees well with the bubbly swarm theory in both analytical calculations and computational simulation. Biot theory also predicts a fast compression wave and a shear wave. The relative contributions of all three wave types are assessed. The effect of the air volume fraction is also investigated. Preliminary experimental measurements of the slow compression wave speed in the lung parenchyma are carried out and agree with theoretical predictions.