Particle Deposition in Oral-tracheal Airway Models with Very Low Inhalation Profiles

Considerable progress has been made on modeling particle deposition in the oral-tracheal airway under some normal breathing conditions, i.e., resting, light activity and moderate exercise. None of these standard breathing patterns correspond to very low inhalation profiles. It is known that particle deposition in the oral-tracheal airway is greatly influenced by flow and particle inlet conditions. In this work, very low inhalation flow rates are considered. Particle deposition is numerically investigated in different oral-tracheal airway models, i.e., circular, elliptic and realistic oral-tracheal airway models. Both micro- and nano-particles that are normally present in cigarette smoke are considered. Results show that inhalation profiles greatly influence the particle deposition. Due to relatively low flow rate, for ultra-fine particles, the oral deposition is enhanced due to longer residence time in oral cavity and stronger Brownian motion. However, for larger particles, less particles deposit in the oral-tracheal airway due to the weaker impaction. The transition happens when particle size changes from 0.01 mu m to 0.1 mu m. The influence of the limited entrance area is shown and discussed. Under the low inhalation profiles, the highest deposition fraction could be in either circular or realistic models depending on the particle property and the geometric characteristic of oral cavity. The knowledge obtained in this study may be beneficial for the design of bionic inhaler and understanding of health effect from smoke particle on human being.