Development of a filter that mimics tracheobronchial deposition of respirable aerosols in humans

In Vitro Estimation of Tracheobronchial and Alveolar Doses Using Filters

“…Figure 2 shows measured filtration for the two layer stainless steel filter noted above, with both layers supplied by ASADA MESH Co. (Osaka, Japan), compared to that predicted by various theoretical deposition models for various breathing patterns. Data obtained at constant flow rates differed negligibly from the corresponding unsteady breathing patterns having the same average flow rate (Tavernini et al, 2019), indicating the filtration efficiencies were unaffected by unsteady flow rates, as was intended in their design. Good agreement is also seen between the measured filtration of the filter and the average tracheobronchial deposition values predicted by the various sources noted in Figure 2, particularly considering the large intersubject variability that is known to occur among the approximately 130 combined subjects of the in vivo scintigraphy studies used to validate the theoretical deposition models (Stahlhofen et al, 1989).…”

“…This is normally done with the aid of single fiber filtration theory (Hinds 1999). However, in our case, we wish to mimic the filtration efficiency of the tracheobronchial region, which involves filter parameter values outside the range of existing single fiber theory equations (Tavernini et al, 2019). Thus, we instead used the computational fluid dynamics (CFD) package OpenFOAM (version 5.0, Bracknell, Berkshire, United Kingdom) to simulate the flow and particle motion through single layers of wire meshes.…”

“…Thus, we instead used the computational fluid dynamics (CFD) package OpenFOAM (version 5.0, Bracknell, Berkshire, United Kingdom) to simulate the flow and particle motion through single layers of wire meshes. CFD was performed for particle diameters in the range of 0.5-10 μm, meshes with wire diameters of 20 and 28 μm with 30.5, 38.1, and 50.8 μm diameter openings, fluid velocities of 0.05-1.55 m/s, and a numerical grid of 1.9-3.2 million cells (see Tavernini et al, 2019 for further details). An empirical curve fit to the CFD results was then used to explore filtration efficiencies for multiple layers of wire meshes for a variety of filter designs.…”