Model of lung parenchyma
In our computational model of lung parenchyma, we combine two complementary approaches to simulate lung tissue at a global scale. For the bulk of lung parenchyma, a constituent-based phenomenological material model has been proposed. To bridge the gap between the global parenchymal and the local alveolar level in regions of particular interest, a suitable multiscale model has been formulated.
Constituent-based material model
Diseases like acute lung injury (ALI), acute respiratory distress syndrome (ARDS) of fibrosis can cause an inhomogeneous alteration of lung tissue. During mechanical ventilation this inhomogeneity can lead to over stretching of healthy tissue regions causing ventilator-associated lung injuries (VALI). To get a better understanding of the under lying processes, causing the changes in material parameters, as well as the impact of this change a sophisticated material model is needed. This model is accounting individually for the contribution of the different load-bearing tissue constituents, i.e. collagen fibers, elastin fibers and the ground substance. To establish this model uniaxial tension tests with lung parenchyma are conducted.
Link to alveolar model (multiscale approach)
Although classical parenchyma models are able to reproduce global lung tissue behavior, a link to the alveolar level is completely missing. However, to investigate mechanisms of VALI, the complex micro-structure has to be taken into account. Therefore, we have developed novel FE2 techniques to resolve the alveolar micro-structure at certain “hot spots”, whereas lung parenchyma is modeled as a homogenized continuum otherwise. The beneﬁt of this approach is twofold; ﬁrstly, improved homogenized parenchyma properties are derived based on a detailed modeling of the underlying micro-structure. Secondly, the global parenchyma model serves as an “embedding” of locally resolved alveolar structures, thereby providing physiologically reasonable boundary conditions on the micro-scale. As a consequence, the quantities of interest on the alveolar level (e.g. stresses and strains in case of VALI) can be simulated more realistically compared to previous models.
Please find publications on our parenchyma models here.