Particle transport and deposition analysis in planar vs. non planar 3D upper airway models with different number of branches

The respiratory system is a vital component of our body. In some cases, it can be affected by diseases that impair the proper functioning of the airways. The main treatment for pulmonary pathologies, as asthma, involves the administration of specific drugs into the system through appropriate inhaler devices. A related area of investigation concerns the interaction between pollutants, which exist in the form of toxic particles in the air, and airways. For a better understanding of particle distribution and transport during inhalation, researchers are focusing on replicating these phenomena using computational fluid dynamics models. Up to now, most of the geometric models used in this field are planar and include the first 3 or 4 generations of branches of the tracheobronchial tree. Fewer models are not-planar or CT-based, have multiple generations of branches and include both the upper airways and an inhaler device. The purpose of this thesis is to compare two of the most commonly used models, ”Weibel’s model” and the ”Typical path lung model”, with a non-planar 3D model generated by ”Lung4cer” software. Results have detected some differences between the models regarding the deposition of particles with a diameter of 10 μm. In particular, the “Typical path lung model” exhibits lower deposition in the oral cavity and more particles travelling to the lung with respect to the other models. Instead, smaller particles have low or null deposition in all cases. As the human lungs are not planar, among the three models, the deposition pattern is more realistic in the non-planar one. This model has subsequently been expanded to comprehend additional generations of branches for a deeper investigation. In these cases, between non-planar models comprising up to 1025 terminal branches, outcomes are generally comparable. The percentage of particles passing through the outlets, for high flow rate, as 60 L/min, is lower than 25% and 30% for particles with diameters of 10 μm and 5 μm respectively. Instead, for 1 μm particles at least 75% of them reach the deeper regions of the bronchial tree. This analysis could contribute to understanding particle behaviour in the airways, in order to enhance the precision of the aforementioned medical devices in reaching the targeted zones, consequently improving the therapies and the quality of life of the patients.