VHC performance evaluation at constant flow: 30 L/MIN

Abstract

Asthma treatment provided by a pressurized Metered Dose Inhaler (MDI) coupled to a Valved Holding Chamber (VHC), in cases of children younger than 5 years old, is a standard well-stablished in the medical community. The lack of experimental studies for comparison of several commercial VHC alternatives is the main goal of this study. The VHC device needs to be evaluated in terms of Fine Particle Mass (FPM) emitted and Performance. Such assessment was made based on a cascade impaction methodology (i.e. Multi-Stage Liquid Impinger - MSLI) at 30 ± 5 L/min. This impactor apparatus is composed by five stage of impaction, where the spray particle size distribution is collected by ranges of aerodynamic diameter, from coarse to fine particles. This evaluation was executed for 8 VHC devices: Aerochamber Plus®, A2A Spacer®, Compact Space Chamber Plus®, Space Chamber Plus®, Nebuchamber®, Vortex®, OptiChamber Diamond® and Volumatic®. The Ventolin® (salbutamol sulphate 100 μg/dose) was the chosen MDI device, due to its widely prescription and acceptance. Drug mass per stage was quantified by UV-Vis Spectrometry, through washing solutions of NaOH 0.01M. Results show clear distinction between the use of MDI alone or coupled with any VHC. Its Emitted Dose (ED) is higher when coupled to a VHC, although the FPM emitted is not different. In other hand the use of VHC provides a reduction from 82.7% to 95.3% of the Throat deposition in comparison to MDI alone. Results point the Aerochamber, Volumatic and Nebuchamber as the highest FPM emitters (27.5 ± 2.4 μg, 27.3 ± 2.7 μg, 26.5 ± 1.8 μg) and with high performance indexes (5.3 ± 0.1, 6.6 ± 1.3, 5.0 ± 0.4). A complete device characteristics analysis is provided, showing that Throat deposition is highly related to the valve design. The Leaflet design (≈5.0 μg) has lower throat deposition than Duck type (≈9.5 μg). A Handling and Attractiveness index is calculated and plotted against the Performance index divided by the device cost. This analysis shows that Volumatic is the best investment (1.73 ± 0.34 £−1) for home / hospital use (2.0 g−1·m−3), while the Aerochamber shows the best portability (53.2 g−1·m−3) and a reasonable investment (1.10 ± 0.02 £−1).