title: A cascade impactor entry port for MDI sprays with collection characteristics imitating a physical model of the human throat.
abstract: OBJECTIVE
  This work was performed in order to compare and contrast results obtained from cascade impactor measurements on metered dose inhalers (MDIs) using a variety of inlet ports.
  
  
  METHODS
  The collection characteristics of four cascade impactor ports (a physical model of the human throat, a simplified geometry intended to mimic the physical model, and two currently-used ports) were measured on a variety of MDI formulations.
  
  
  RESULTS
  The portion of the MDI spray which collects on the entry port depends in a complicated fashion on the characteristics of the formulation; in these studies the fraction of the total dose which was collected on the port ranged between about 20% and 90% of the total emitted dose. The collection characteristics of the simplified geometry closely corresponded to the physical model. The length of the flow path between the port and the impactor was varied, and found not to have a strong effect on the measured size distribution passing the port.
  
  
  CONCLUSIONS
  Ranking of various MDI formulations according to performance criteria as measured with a cascade impactor should be expected to depend on the particular inlet port which is used.
authors.affiliation: Inhalation Technology Laboratory, 3M Center, St. Paul, Minnesota 55144, USA.
authors.forename: N C
authors.initials: NC
authors.lastname: Miller
authors.forename: A M
authors.initials: AM
authors.lastname: Purrington
mesh_terms: D000280:Administration, Inhalation; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D006801:Humans; D008953:Models, Anatomic; D009330:Nebulizers and Vaporizers; D010614:Pharynx / Q000033:anatomy & histology*