Quantitative study of Artemisia pollens deposition in the upper airways of children with adenoidal hypertrophy

Studies regarding the pollen transport and deposition in children nasal airways are still scarce, especially the regional deposition doses, which is difficult to provide guidance for precise application of pollen blockers and nasal administration. In addition, most previous investigations included only one child case, which lacked statistical significance. To this end, we used computational fluid particle dynamics (CFPD) modeling approach to calculate the deposition pattern of Artemisia pollen at various anatomical sites in the upper airway of 12 children with adenoid hypertrophy (AH), and analyzed the effects of respiratory flow rate and pollen density on the deposition distribution. Adult nasal airways from our previous study were included for data comparison. We found that nasal cavities of children with AH aged 4-6 years had a greater area/ volume ratio than adults did, and the area and volume of the turbinate region were less than half that of adults. The physical diameter of Artemisia pollen was set to 21.0 mu m, with a shape of ellipsoid. Its average density is 1080 kg/m3 in the humid state and 550 kg/m3 in the dry state. In resting state, children with AH had higher deposition rates of wet Artemisia pollen in the nasal septum and nasopharynx, and lower deposition rates in the nasal vestibule and middle turbinate compared with adults. Under exercising conditions, wet pollen was deposited mainly in the nasal vestibule and the anterior part of the nasal septum in children. Compared to wet pollen, the deposition rate of dry Artemisia pollen in resting state was approximately halved and the pollen entering the lower respiratory tract rose approximately 47-fold. The findings suggest that nasal cavities of children are not simply scaled-down version of adults. Notable differences in deposi-tion hotspots and deposition patterns have been discovered between the two. The deposition hotspots shifted significantly forward as the respiratory flow rate increased. Dry Artemisia pollen has a low density and is more likely to enter the lower respiratory airways, which may put children at a higher risk of developing asthma.