Efficiency of Valved Holding Chambers: Numerical Comparison Study at Constant Flow

Authors: , , , ,

Summary
Not all patients have the capacity to properly use a pressurized Metered-Dose Inhaler (pMDI) due to the need to breath-hand coordination. The Valved Holding Chamber (VHC) devices extend the distance between the pMDI and the patient’s mouth. They also contribute to the reduction of the oral pharyngeal spray deposition and allow the patient to breathe normally. The main objective of this work is to numerically evaluate various VHC devices commercially available in terms of mass deposition. Through the use of Computational Fluid Dynamics (CFD) the airflow velocity and turbulence fields were calculated for four geometries (i.e. A2A, Aerochamber, NebuChamber and Volumatic). The airflow fields at 30 L/min allowed the prediction of pMDI drug particle deposition in different zones of the geometry. The evaluation of VHC’s efficiency was done by calculating the different mass deposition fractions for each geometry zone, as well as, the exit Fine Particle Dose (FPD) and Mass Median Aerodynamic Diameter (MMAD). The results show that the Volumatic has the highest body deposition, while the NebuChamber presents the highest USP throat value. The Aerochamber shows the higher valve deposition value. A2A has a lower USP deposition but a high body deposition. Regarding the amount of drug reaching the Cascade Impactor (CI), the Aerochamber presents the best result, as well as, the highest amount of FPD delivered. Meanwhile, the Volumatic has the lowest MMAD value delivered but the worst FPD result. Based on the results, the Aerochamber presents higher FPD available to the CI / lungs.

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