Importance of the Tongue as an Impactor for Orally Inhaled Aerosols from a Pressurised Metered Dose inhaler (pMDI) With and Without a Valved Holding Chamber (VHC)
Mark W Nagel1, Cathy Doyle1, Jason A Suggett1 & Jolyon P Mitchell2
1 Trudell Medical International, 725 Baransway Drive, London, Ontario, N65 5G4, Canada
2 Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Rd., London, Ontario, N6H 2R1, Canada
Summary
We undertook a study comparing fine particle fraction (FPF<4.7 μm) and fine particle mass <4.7 μm aerodynamic diameter (FPM<4.7μm) from a pMDI delivering salbutamol (100 μg/actuation) with and without a VHC. A series of four model adult oropharyngeal cavities (OCs) were used, in which the tongue size was progressively reduced in volume (100%, 60%, 30% and 0%). FPF<4.7μm for the pMDI alone increased significantly (1-way ANOVA, p <0.0001) with reduced tongue volume, from 16.7 ± 3.6% with the full tongue volume present, to 38.5 ± 6.5% when the tongue was completely removed. FPM<4.7μm increased from 12.9 ± 2.1 μg/actuation to 26.5 ± 3.8 μg/actuation (p <0.0001). When the VHC was present, with a 2 s delay between actuation and inhalation the FPF<4.7 μm remained relatively consistent across the different tongue volume conditions, and the FPM<4.7μm changed much less than with the MDI alone. We confirmed the importance of the tongue in controlling fine particle delivery beyond the oropharynx. When the VHC was absent, the data confirmed clinical guidance to insert the mouthpiece above the tongue before actuating and simultaneously inhaling the medication. If a VHC is present, we demonstrated consistent fine particle delivery irrespective of tongue volume, without the need to coordinate actuation with inhalation. Such changes in tongue position may better reflect the variability in human anatomy in inhaler use.