Space Chamber devices in vitro performance evaluation at constant flow

R F Oliveira, S F C F Teixeira, H M Cabral-Marques, J C F Teixeira

The use of spacers is advisable for asthma treatment in younger patients (< 5 years). This work aims to evaluate such devices in terms of performance when compared against the use of pressurized metered-dose inhaler (pMDI) solo. For that purpose an experimental in vitro assessment of four valved holding chambers (VHC) and one tubular spacer was performed using a Multi-Stage Liquid Impinger at 60 L/min. The add-on devices were tested with Ventolin HFA-134a (salbutamol sulphate, as API), and the drug deposited in the setup was recovered with NaOH 0.01M. Solutions concentrations were estimated by UV-Vis spectrophotometry at 244 nm. Results showed that the highest VHC mass deposition was found in the Volumatic®, while the valveless tubular spacer (i.e. Compact Space Chamber Spacer®) has the lowest deposition. Add-on devices throat deposition was found to be lower than the pMDI solo (≈45 μg). Only between the Compact Space Chamber® and the Space Chamber® were not found statistically significant differences in throat deposition (p>0.05). The mass median aerodynamic diameter (MMAD) is lowest for the Volumatic® and highest (2.3±0.1 μm) for the valveless tubular spacer (3.2±0.3 μm), with statistical differences between the add-on devices (p<0.001). The MMAD for VHCs with leaflets valve type showed no significant differences (p>0.05). Fine particle mass (FPM) between the add-on devices showed no differences (p>0.05). The highest FPM is provided by Volumatic® (36.5±2.4 μg) and the lowest Compact Space Chamber Anti-static® (32.9±3.2 μg). The pMDI solo emits lower FPM (29.3±3.4 μg). The calculation of the coarse/fine/extra-fine particle fractions and coarse/fine/extra-fine ratios showed that all the add-on devices have similar performance results for all the calculated metrics, being within the reference values. Add-on devices provide the reduction of the coarse fraction of the pMDI plume and, subsequently, the reduction of the throat deposition. The existence (or not) of a valve, even the type of valve, has influence in the mass deposited inside the VHC and in the throat.

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