Inhalation of toxic and therapeutic particles in a human nasal cavity

The reconstruction of the nasal cavity from computed tomography (CT) scans to a computational model was performed in order to (i) analyse the air flow field and (ii) particle dynamics. The scans were converted into MegaWave2 in preparation for processing. The solid modeling program, CATIA combined with the meshing program GAMBIT was then used to establish a model ready for Computational Fluid Dynamics (CFD) analysis. A steady state laminar flow at 7.5L/min was used to capture the flow field. Complex flow patterns including vortices were found in the nasal valve region. This flow feature enhances the deposition patterns in the anterior region of the cavity. Fibrous particles and low density particles were introduced into the air flow stream with their trajectories and deposition location recorded. Low-density drug particles lightens the particle inertial properties however the particle inertia is more sensitive to the particle size rather than the density. The toxicity of fibres has been linked to its length where fibre deposition in the lungs can be carcinogenic. It was found that asbestos had very low deposition, ≈10% and was independent of fibre length, leading to deep lung deposition. In comparison, the carbon fibre was more sensitive to changes in the length and exhibited increases in deposition as the fibre length increased.