Inhalation is the most important route of entry for aerosol particles. Deposition in the respiratory tract is affected by many factors, such as particle size, shape, charge, density, breathing pattern and physical tract structure. However, most of the currently available lung deposition data are on Caucasians, with very limited data on Taiwanese. Therefore, it is essential to clarify whether there is a significant difference in respiratory tract deposition between Caucasian and Taiwanese individuals. This work is thus aimed at characterizing regional lung deposition in Taiwanese.
A rapid method of measuring regional lung deposition 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 oral breathing, nasal breathing was also conducted. A special respirator was employed to facilitate measurements of the nasal route deposition. The regional lung deposition data obtained in this work showed good agreement with previous studies based on the bolus technique, indicating that the difference in lung deposition between Taiwanese and Caucasian individuals is negligible. The local deposition efficiency increased with the penetration volume. This increased trend was particularly prominent in the deep lungs, which was likely due to the dilution effect caused by the relatively clean air in the functional residual capacity. When a fixed fraction of the forced vital capacity was used to replace the fixed tidal volume, the total lung deposition became less dependent on the tidal volume. Primarily due to nostril hairs and the complex configuration of the nasal turbinate, the local deposition efficiency of the nasal route was higher than that of the oral route but only in the early stage of penetration (200 mL).