EXPERIMENTS ON PARTICLE DEPOSITION IN THE HUMAN UPPER RESPIRATORY SYSTEM

In this study, the deposition of particles (0.3 mu m to 2.5 mu m in di ameter) within a silicone rubber model of the human upper respiratory system was studied. The domain of the respiratory tract under investig ation begins at the entrance (nostrils and mouth) and continues throug h to the second generation of the tracheobronchial airways (main bronc hi). The particle deposition efficiency of the sample respiratory syst em was computed by measuring particle concentration at the inlet and o utlet of the model. The regional deposition patterns of fluorescent pa rticles (0.3 mu m to 0.7 mu m in diameter) was examined by measuring t he fluorescent intensity with a fluorescence spectrophotometer. For si mulated oral inhalation, the deposition efficiency of the oral cavity (0.9%-5.4%) is approximately the same as that of the oropharynx-trache a region (0.8%-4.8%). During simulated nasal inhalation, the depositio n efficiency of the nasal region (20%-43.6%) is greater than the value s of the nasopharynx-trachea region (2.8%-8.2%). The nasopharynx-trach ea region exhibits a higher deposition efficiency than that of the oro pharynx-trachea region. Deposition during the simultaneous oral and na sal inhalation is mostly affected by particle size. Flow rate through the model has less effect on deposition for particle diameter less tha n 1 mu m. When particle diameter is greater than 1 mu m, deposition ef ficiencies are weakly and inversely related to the flow rate, (C) 1998 American Association for Aerosol Research.