Abstract:
The distribution o f blood flow through the lung is influenced by the branching geomet ry o f the pulmonary vascular t rees and the cal iber o f the vessels through which the blood flows. Vessel cal iber is determined by the vessel's elasticity, and the relationship between radius and local pressure. Therefore in o r d e r to understand heterogenei ty in pulmonary blood flow distribution, it is important to use a physically realistic geomet ry and a computational model that couples blood flow and soft tissue mechanics. We have coupled existing models o f pulmonary blood flow to equat ions for large deformat ion elasticity to predict regional pressures throughout the lung during volume changes. Geometric models o f the lung and largest blood vessels are derived from multi detector row x- ray computed tomography scans from the Lung Atlas project [1]. A volume-filling branching algorithm is applied to obtain additional blood vessels unidentifiable via imaging. Solution o f a reduced form o f the Navier-stokes equat ions through the vascular geomet ry - with the addition o f a p r e s s u r e - r a d i u s relationship - y i e l d s pressure, flow, and radius information. Pressure fields computed from elastic deformat ion o f the lung are coupled to the constitutive law that def ines the relationship between transmural pressure and vessel radius. Patterns o f flow and flow heterogenei ty are analyzed using this physically realistic vascular geomet ry with regional tissue pressures in response to the magnitude o f gravity and orientation o f the lung model. Vessel elasticity is found to have a significant effect on the distribution o f flow, with more elastic vessels leading to a more pronounced gradient o f flow due to gravity.