Section: New Results

Lung and respiration modeling

Participants : Céline Grandmont, Dena Kazerani, Nicolas Pozin, Marina Vidrascu, Marc Thiriet, Irene Vignon Clementel.

In [30] we use the coupled model tree-parenchyma model introduced in [31] to study the impact of asthma on effort and ventilation distribution along with the effect of Heliox compared to air. Indeed, in spite of numerous clinical studies, there is no consensus on the benefit Heliox mixtures can bring to asthmatic patients in terms of work of breathing and ventilation distribution. For this study, lung surface displacement fields extracted from computed tomography medical images are used to prescribe realistic boundary conditions to the system. Asthma is simulated by imposing bronchoconstrictions to some airways of the tracheo-bronchial tree based on statistical laws deduced from the literature. This study illuminates potential mechanisms for patient responsiveness to Heliox when affected by obstructive pulmonary diseases. Responsiveness appears to be function of the pathology severity, as well as its distal position in the tracheo-bronchial tree and geometrical position within the lung. Moreover, as already stated, in asthma and COPD, some airways of the tracheo-bronchial tree can be constricted, from moderate narrowing up to closure. These pathological patterns affect the lung ventilation distribution. While some imaging techniques enable visualization and quantification of constrictions in proximal generations, no non-invasive technique provides precise insights on what happens in more distal areas. In [44] we propose a process that exploits dynamical lung ventilation measurements to access positions of airways closures in the tree. This identification approach combines our lung ventilation model along with a machine learning approach. Based on synthetic data generated with typical temporal and spatial resolutions as well as reconstruction errors, we obtain encouraging results with a detection rate higher than 90%.

The human tracheobronchial tree surface is covered with mucus that ensures clearance of foreign material. An alteration of mucus or its environment such as in cystic fibrosis dramatically impacts the mucociliary clearance. In [48] the numerical method is able to manage variations of more than 5 orders of magnitude in the shear rate and viscosity. It leads to a cartography that enables to discuss major issues on defective mucociliary clearance in cystic fibrosis. In addition, cystic fibrosis is associated with a shear-thinning mucus that tends to aggregate in regions of lower clearance. However, a rarefaction of periciliary fluid has a greater impact than the mucus shear-thinning.