Ultrafine particle transport to the lower airways: airway diameter reduction effects

Toxic nanoparticles, also called ultrafine particles, pose a significant risk to human respiratory health. During inhalation, toxic particles may escape to the lower generations of the human lungs due to their tiny size. Understanding the transport process of ultrafine particles in lungs significantly supports respiratory tract health-risk assessment. While nanoparticle transport in the airflow and deposition of particles in the oral, nasal, and upper parts of the respiratory tract have been described, age-related airway reduction effects in transport to the lower airways remain unknown. This chapter provides a modeling approach for ultrafine particle deposition in lungs for three age-related lung sizes, different flow rates, and various nanoparticle sizes. The Euler-Lagrange (E-L) method was applied to model nanoparticle deposition. Findings from this in silico study show, for example, a significant pressure drop from generation 1 to generation 2 of the 60-year-old lungs, while the 50- and 70-year-olds had a significant pressure drop from generation 4 to generation 5. Total particle deposition in the models depended on flow rate, lung geometry, and particle size. Improved understanding of the deposition fraction (DF) in each lung section will likely prove useful for optimizing drug delivery transport to the terminal bronchioles and the alveolar region.