Empirical Equations for Nasal Deposition of Inhaled Particles in Small Laboratory Animals and Humans

Based upon available experimental data, a set of empirical equations was derived for nasal deposition efficiency of inhaled particles in the inertial deposition range for four small laboratory animal species: the mouse, hamster, rat, and guinea pig. An equation for nasal deposition in humans was also derived in the same mathematical form to facilitate interspecies comparison. In these equations, deposition efficiency was expressed as a function of particle inertia d2 a Q where da is the particle aerodynamic diameter and Q is the flow rate. Results from the empirical equations showed that nasal deposition was species dependent, and that at the same d2 a Q, species with smaller body weight had higher deposition efficiency. By incorporating the anatomical data of the nasal passage, the deposition equations were rewritten as a function of the product of Stokes number and the total bend angle in nasopharynx. Interspecies deposition differences were found to be greatly reduced in terms of the new variable.