Application of CFD to transient flows in compliant lungs

Patient-specific simulation of flows in lungs is now straightforward, by segmenting scans from CT and other imaging techniques, creating surface meshes of the lower airways, and using these as the geometries for a computational fluid dynamics (CFD) simulation. The resulting flows have been used to aid drug deposition studies and the treatment of asthma and COPD. The Airprom project is a European collaborative project aiming to predict the natural history of airways diseases through patient-specific multi-scale computational models and to investigate if models can predict the magnitude of the effect of a theoretical, new or current therapy required within an individual to translate into an important clinical outcome. These computational models have not realised their full clinical potential, as they have not been extensively validated in large cohorts of well characterised patients. Consequently, their ability to predict future outcomes has not been fully defined. One aspect of Airprom is to automate the simulation of the flows in the lower conducting airways, the intrapulmonary airways, from the trachea to about the sixth branch, taking realistic conditions into account. This will allow the methodology to be applied to a large number of patients and hence help to validate the outcomes of the simulations and its role in predicting the natural history and response to therapy in airway disease. This paper considers one aspect of this work, focussing on the motion of the lungs during the breathing cycle, and how this affects the resulting flows and airway resistances, as well as the effect of compliance in the lung geometry. The approach adopted is also capable of being used on medical applications, where the geometry is highly dynamic and defined from medical images