Brownian dynamics of nano-fibers in human upper tracheobronchial airways

Transport and deposition of inhaled asbestos fibers has been studied in the past few decades due to its pathological response in living being. In the earlier studies, in vitro and vivo experiments in human and animal subjects were reported; however, the reported computational studies are sparse. In this work, the transport and deposition of nano-fibers were simulated in a physiologically realistic lung bifurcation model. Focus of this study was to explore the effect of the Brownian dynamics on the very thin fibers, and how it affects the transport and deposition of the fibers in human airway passages. Motion of the inhaled fibers and their interactions with the surrounding environment were reproduced by solving the system of coupled nonlinear equations governing the fiber translational and rotational motions. Hydrodynamic drag and torque, turbulence dispersion, gravitational sedimentation, and the Brownian diffusion were accounted for. The study uncovered the very important role of Brownian dynamics in thin fibers' motion in human tracheobronchial airways. The simulation results were compared with the experimental measurements, and the carcinogenicity of these fibers in human airways was discussed. The simulation results can help explain many of the earlier experimental findings.