Experimental assessment of Emitted Dose from Valved Holding Chamber devices

Abstract

Due to the increasing worldwide incidence of asthma, a growing usage of inhalation devices has been observed. Some of the pressurized Metered Dose Inhalers (pMDI) limitations have been overcome by the introduction of newly and improved Valved Holding Chambers (VHC), resulting in good patient acceptance.The efficiency is assessed by the VHC Emitted Dose (ED), i.e. the amount of drug available to the patient.Using the pMDI salbutamol sulfate formulation (Ventolin (R) HFA-134a) as the test drug, several VHC devices were assessed. These latest were grouped by material characteristics: dissipative (OptiChamber Diamond (R), AeroChamber Plus (R), Vortex (R), A2A Spacer (R)), non -dissipative (SpaceChamber Plus (R), Compact SpaceChamber Plus (R), Volumatic (R)) and stainless steel (Nebuchamber (R)).The pMDI + VHC were assembled to a filter housing, which comprises an induction port with similar USP Throat dimensions, and connected to a vacuum pump (calibrated at 15, 26 and 40 L/min). Using UV-Vis Spectrophotometry equipment at 244 nm, it was possible to determine its concentration for later mass calculation. For all the VHC devices tested, the total mass recovery percentage was between 85% and 120%.At 26 L/min, the Vortex (R) VHC has shown the highest ED (47.3 +/- 1.8 %).The ED may not be dependent on the volume of the VHC. Although, further analysis of the results suggests the existence of a linear correlation between the ED and the VHC body length.SpaceChamber Plus (R) results show an increase of the ED and, subsequently, a decrease in VHC deposition fraction, with the increase of airflow.