© 1991 Oxford University Press
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In VivoDeposition of Ultrafine Aerosols in the Nasal Airway of the Rat
Inhalation Toxicology Research Institute, Lovelace Biomedical and Environmental Research Institute P.O. Box 5890, Albuquerque, New Mexico 87185
Received June 25, 1990; accepted September 27, 1990
We studied the deposition of ultrafine aerosols, ranging in geometric diameter from 0.005 to 0.1 µm, in the nasal airway of Fischer-344/N rats, at inspiratory flow rates of 200, 300, 400, and 600 ml/min. Simultaneously, we measured the pressure drop across the rat nasal airway. The purpose was to determine whether the in vivodeposition of ultrafine aerosols in the rat nasal airway is the same as the deposition observed in rat nasal casts. At a flow rate of 400 ml/min, corresponding to the normal mean inspiratory flow rate of the rat, deposition efficiency increased from 6 to 58%, when the particle diameter decreased from 0.1 to 0.005 µ m. For 0.005-µm-diameter particles, the deposition efficiency decreased from 68 to 52% when the flow rate was increased from 200 to 600 ml/min. These results agree well with those from previous experiments with nasal casts, which indicated that diffusion is the dominant mechanism for deposition of ultrafine aerosols. The pressure drop in the nasal airway of the rat increased almost linearly with flow rate, from 73 Pa at 200 ml/min to 247 Pa at 600 ml/min. These values are within the range of those obtained in previous experiments with nasal casts, although the pressure drop in casts increased as a power > 1 with flow rate. The results of our study support the use of nasal airway casts to estimate the in vivodeposition of ultrafine aerosols.