title: The interaction between the oropharyngeal geometry and aerosols via pressurised metered dose inhalers.
abstract: OBJECTIVE
  This study investigated the effect of oropharyngeal geometry on inhaled aerosol characteristics via pressurised metered dose inhalers (pMDIs), both with or without spacers.
  
  
  METHODS
  Seven adult oropharyngeal models with different centreline lengths, total volumes, and degrees of constriction were employed as induction ports for a laser diffraction particle size analyser and cascade impactor. Particle size change over time, mass median aerodynamic diameter (MMAD), average median volume diameter (D(V)50), inhaled doses, and oropharyngeal depositions (percentage of the nominal dose) for aerosols via suspension and ultrafine pMDIs with or without spacers at 30 l/min airflow were determined.
  
  
  RESULTS
  Variations in oropharyngeal geometry caused significant variations in inhaled particle size distributions, doses, oropharyngeal drug depositions, and particle size change over time when pMDIs were used without spacers. However, inhaled aerosol characteristics had marginal variations for the ultrafine pMDI plus large volume spacer (MMAD range: 0.69-0.78 microm, D(V)50 range: 1.27-1.36 microm, inhaled dose range: 46.46-52.92%). It was found that the amounts of inhaled aerosol particles with aerodynamic size of less than 0.83 microm via pMDIs plus large volume spacer were slightly affected by the oropharyngeal geometry.
  
  
  CONCLUSIONS
  Inhaling ultrafine aerosols via spacers may reduce the effect of oropharyngeal geometry on inhaled aerosol properties.
authors.affiliation: School of Pharmacy & Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK. t.ehtezazi@ljmu.ac.uk
authors.forename: T
authors.initials: T
authors.lastname: Ehtezazi
authors.forename: I
authors.initials: I
authors.lastname: Saleem
authors.forename: I
authors.initials: I
authors.lastname: Shrubb
authors.forename: D R
authors.initials: DR
authors.lastname: Allanson
authors.forename: I D
authors.initials: ID
authors.lastname: Jenkinson
authors.forename: C
authors.initials: C
authors.lastname: O'Callaghan
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000336:Aerosols / Q000008:administration & dosage / Q000493:pharmacokinetics*; D016503:Drug Delivery Systems / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D036503:Inhalation Spacers; D036501:Metered Dose Inhalers; D008953:Models, Anatomic; D009960:Oropharynx / Q000033:anatomy & histology* / Q000378:metabolism; D010316:Particle Size; D013535:Suspensions; D014018:Tissue Distribution
chemical_list: D000336:Aerosols; D013535:Suspensions