Scientific Publications by FDA Staff

Int J Numer Method Biomed Eng 2017 Jul;33(7):e2838

A Quasi-3D wire approach to model pulmonary airflow in human airways.

Kannan RR, Chen ZJ, Singh N, Przekwas A, Delvadia R, Tian G, Walenga R

The models used for modeling the airflow in the human airways are either 0D compartmental or full 3D Computational Fluid Dynamics (CFD) models. In the former, airways are treated as compartments and the computations are performed with several assumptions, thereby generating a low fidelity solution. The CFD method displays extremely high fidelity since the solution is obtained by solving the conservation equations in a physiologically consistent geometry. However, CFD models (i) require millions of degrees of freedom (DOF) to accurately describe the geometry and to reduce the discretization errors, (ii) have convergence problems and (iii) require several days to simulate a few breathing cycles. In this paper, we present a novel, fast-running and robust Quasi-3D (Q3D) wire model for modeling the airflow in the human lung airway. The wire mesh is obtained by contracting the high fidelity lung airway surface mesh to a system of connected wires, with well-defined radii. The conservation equations are then solved in each wire. These wire meshes have around O(1000) DOF and hence are 3000-25000 times faster than their CFD counterparts. The 3D spatial nature is also preserved since these wires are contracted out of the actual lung STL surface. The pressure readings between the two approaches showed minor difference (maximum error = 15%). In general, this formulation is fast, robust, allows geometric changes and delivers high fidelity solutions. Hence, this approach has great potential for more complicated problems including modeling of constricted/diseased lung sections and for calibrating the lung flow resistances through parameter inversion.