Computational fluid-particle dynamics method in predicting the particle aspiration and deposition in the comprehensive monkey respiratory tract.

BACKGROUND AND OBJECTIVES

Extrapolating dose-response data from laboratory animals is a common approach for assessing human health risks associated with inhalation exposure to foreign toxic substances. Although monkey-based experiments represent a suitable alternative for human exposure studies, they are strictly restricted by animal protection and ethical barriers. Therefore, numerical efforts to elucidate particle transportation and deposition characteristics in the monkey airway are required. Besides, natural interspecific discrepancies in airway structure may result in validation of particle aspiration and deposition efficiencies. Hence, this study aims to predict the particle aspiration and deposition efficiencies in the monkey airway and compare them to those of humans.

METHODS

A numerical airway model of rhesus macaques was constructed from the nostrils down to the 33rd generation. Herein, steady and transient breathing patterns were considered under resting conditions employing the Eulerian descriptions for the flow field, then particle tracking for diameters ranging from 1 to 80 μm was performed using the Lagrangian particle tracking.

RESULTS

Validation works against experimental and numerical data were conducted to confirm a highly reliable simulation. Targeting the flow field, differences between the left and right sides were observed at the large bronchi under unsteady breathing conditions. Compared to humans, the aspiration efficiency was relatively higher for particle sizes up to 30 μm, but exhibits a lower distribution from the size of 40 μm. Quantitative particle deposition indicates a significant deviation between monkey and human in upper and lower airways for the particle size less than 20 μm. The regional deposition analyses in the lung bifurcation region exhibited a pronounced peak deposition at the fourth bifurcation, which predominantly occurred in the left lung.

CONCLUSIONS

These findings unveil valuable insights into the particle behaviors in monkey bifurcation models. In addition, these results can also enrich the current knowledge about the prediction of inhaled substance exposure in the respiratory system and emphasize the importance of animal models.