Inhaled drug airflow patterns and particles deposition in the paediatric respiratory tract.

Purpose: The effectiveness of inhaled drugs is strictly related to areas reachable by drug particles. Unless particles reach the desired part of the bronchial tree, their influence might not meet the expectations. Consequently, the disease progress might not be stopped or even slowed down. Therefore, the primary objective of this research was to analyze the airflow patterns and particle deposition of a standard inhaled drug using computational fluid dynamics. Methods: The study was devoted to the analysis of the particle diameter influence on their deposition areas within the entire respiratory tract. Two patient-specific respiratory tract models, for 6 and 12-year-old patients, were reconstructed based on the computed tomography examinations. Numerical analyses were carried out as stationary ones with the constant inflow of the particles of various diameters (within the range of 1-50 mu m). It was proven that depending on the particle size, their deposition within the respiratory tract varies significantly. Results: The vast majority of the particles with diameters over 20 mu m is gathered on the walls of the throat, whereas particles of diameters 5-15 mu m are accumulated mainly on the trachea walls, leaving the alveoli insufficiently supplied with the drug particles. Conclusions: The inhaled drug size cannot be treated as negligible factor during the drug spraying. An improper distribution of the particles might not inhibit the symptoms of the asthma. Numerical simulations may improve drugs selection and visualize their distribution along the airways, which might accelerate asthma treatment personalization.