Advanced multi-scale modelling of the respiratory system

This chapter is concerned with computational modelling of the respiratory system against the background of acute lung diseases and mechanical ventilation. Conceptually, we divide the lung into two major subsystems, namely the conducting airways and the respiratory zone. Due to their respective complexity, both parts are out of range for a simulation resolving all relevant length scales. Therefore, we develop novel multi-scale approaches taking into account the unresolved parts appropriately. In the respiratory zone, an alveolar ensemble is modelled considering not only tissue behaviour but also the influence of the covering surfactant film. On the global scale, a homogenised parenchyma model is derived from experiments on living lung tissue. At certain hotspots, novel nested multi-scale procedures are utilised to simulate the dynamic behaviour of lung parenchyma as a whole while still resolving alveolar scales locally. In the tracheo-bronchial region, CT-based geometries are employed in fluid-structure interaction simulations. Physiological outflow boundary conditions are derived by considering the impedance of the unresolved parts of the lung in a fully coupled 3D-0D procedure. Finally, a novel coupling approach enables the connection of 3D parenchyma and airway models into one overall lung model for the first time.