Micron-sized and submicron-sized aerosol deposition in a new ex vivo preclinical model

BACKGROUND: The knowledge of where particles deposit in the respiratory tract is crucial for understanding the health effects associated with inhaled drug particles. METHOD: An ex vivo study was conducted to assess regional deposition patterns (thoracic vs. extrathoracic) of radioactive polydisperse aerosols with different size ranges [0.15 μm–0.5 μm], [0.25 μm–1 μm] and [1 μm–9 μm]. SPECT/CT analyses were performed complementary in order to assess more precisely the regional deposition of aerosols within the pulmonary tract. Experiments were set using an original respiratory tract model composed of a human plastinated head connected to an ex vivo porcine pulmonary tract. The model was ventilated by passive expansion, simulating pleural depressions. Aerosol was administered during nasal breathing. RESULTS: Planar scintigraphies allowed to calculate the deposited aerosol fractions for particles in the three size ranges from sub-micron to micron The deposited fractions obtained, for thoracic vs. extra-thoracic regions respectively, were 89 ± 4 % vs. 11 ± 4 % for [0.15 μm–0.5 μm], 78 ± 5 % vs. 22 ± 5 % for [0.25 μm–1 μm] and 35 ± 11 % vs.65 ± 11 % for [1 μm–9 μm]. CONCLUSION: Results obtained with this new ex vivo respiratory tract model are in good agreement with the in vivo data obtained in studies with baboons and humans.