Particle deposition in human nasal airway replicas manufactured by different methods. Part II: Ultrafine particles

Information on the deposition of ultrafine particles in nasal airways is important for assessing the risks of exposure to airborne particulate matter and for understanding drug delivery implications for particles of this diameter. Nasal particle deposition is often studied using plastic replicas of nasal airways. Ultrafine particle deposition has been measured previously in replicas of nasal and upper airways that were manufactured from magnetic resonance images or cadaver specimens. Here we determined the deposition efficiency of two replicas of the same nasal airways manufactured by different stereolithography processes and investigated the sensitivity of ultrafine particle deposition to differences in nasal airways by comparing results from our nasal replicas with those of other models. Two replicas of the same nasal airways were manufactured from a finite-element mesh using stereolithography machines with different resolutions. Deposition efficiency of the replicas was measured for particle diameters between 0.005 and 0.15 mum and constant inspiratory flow rates of 10 and 20 l/min. Deposition efficiency was less than 10% for particles > 0.03 mum and increased for particles < 0.03 mum. The increase correlated with increased particle diffusivity. Deposition in the replicas was similar within the scatter of the measurements. Reasonable agreement was found between our deposition measurements and those reported previously for other models. Small differences in deposition measurements for the various nasal replicas could not be attributed to differences in methods used to manufacture the replicas. Ultrafine particle deposition results for nasal replicas suggest that small differences in nasal airways have minimal effect on nasal deposition efficiency for particles <0.15 mum.