Experiments on Particle Deposition in the Human Upper Respiratory System

In this study, the deposition of particles (0.3 mm to 2.5 mm in diameter) within a silicone rubber model of the human upper respiratory system was studied. The domain of the respiratory tract under investigation begins at the entrance (nostrils and mouth) and continues through to the second generation of the tracheobronchial airways (main bronchi). The particle deposition efficiency of the sample respiratory system was computed by measuring particle concentration at the inlet and outlet of the model. The regional deposition patterns of fluorescent particles (0.3 mm to 0.7 mm in diameter) was examined by measuring the fluorescent intensity with a fluorescence spectrophotometer. For simulated oral inhalation, the deposition efficiency of the oral cavity (0.9%–5.4%) is approximately the same as that of the oropharynx-trachea region (0.8%–4.8%). During simulated nasal inhalation, the deposition efficiency of the nasal region (20%–43.6%) is greater than the values of the nasopharynx-trachea region (2.8%–8.2%). The nasopharynx-trachea region exhibits a higher deposition efficiency than that of the oropharynx-trachea region. Deposition during the simultaneous oral and nasal inhalation is mostly affected by particle size. Flow rate through the model has less effect on deposition for particle diameter less than 1 mm. When particle diameter is greater than 1 mm, deposition efficiencies are weakly and inversely related to the flow rate.