Inhalation is the most important route of entry for aerosol particles. Aerosol deposition in the respiratory tract is affected by many factors, such as particle size, shape, charge, density, breathing pattern and the physical structure of the respiratory tract. However, currently available lung deposition data are mostly on Caucasians. Lung deposition data on Taiwanese are very limited. Therefore, it is essential to clarify whether there is a significant difference in respiratory tract deposition between Caucasians and Taiwanese. Thus, this work aimed to characterize regional lung deposition in Taiwanese.
A rapid regional lung deposition measurement method was employed in the present study. The experimental system consisted of an aerosol chamber, a mouthpiece, a pneumotachograph flow meter, and a particle counter. A cylinder-piston type breathing machine was used to generate a series of ‘standard’ breathing patterns for subjects to follow. In addition to mouth breathing, nose breathing was also conducted. A special respirator was employed to facilitate the measurements of nasal route deposition. The regional lung deposition data obtained in this work showed a good agreement with previous studies based on the bolus technique, indicating the difference in lung deposition between Taiwanese and Caucasians is negligible. The local deposition efficiency increased with penetration volume. This increased trend was particularly prominent in the deep lung, which was likely due to the dilution effect caused by the relatively clean air in the functional residual capacity. When a fixed fraction of forced vital capacity was used to replace fixed tidal volume, the total lung deposition became less dependent on the tidal volume. The nasal route local deposition efficiency was higher than that of the mouth route, but only in the early stage of penetration volume of 200 mL. This increase was mainly due to the nostril hairs and the complex configuration of the nasal turbinate