Oropharyngeal cast as a filter of inhaled particles

Filtration efficiency in the human headways during inhalation is studied based on the emitted dose of the drug, loss of particles in the oropharynx and particle size distribution. Perfect synchronization of actuation and inspiration for continuous flow of 30 l/min allowed 16% of the particles dose to penetrate into the trachea. However, only 9% particles penetrated when the inspiration was 1s after actuation. Analysis of particle size distributions indicates that the wide spectrum of particle diameters is significantly reduced passing the cast to particles with diameters below 8 mu m. An inertial impaction is the main mechanism of particles deposition in the oropharyngeal cast.