Experimental analysis of particles flow inside the Volumatic ® spacer

At present there are several studies regarding the performance of many pressurized metered-dose inhalers (pMDIs), more precisely, spacers with special emphasis on the study and analysis of the fluids using (Computational Fluids Dynamics (CFD) software, in this specific case, Fluent™. The Volumatic ® is the most commonly used spacer nowadays, and, therefore, the one that has been studied more. However, and in spite of all the simulations carried out with air and drug particles, there is no confirmation with an actual experimental testing procedure regarding the drug dynamics inside a particular spacer. Therefore, and to validate the simulated studies carried out before in this area, a mechanical system able to duplicate the respiratory system was designed and implemented so that the same conditions inputted to the simulation tools could be tested and compared. In order to collect the data for this analysis, the Laser Doppler Anemometry (LDA) technique was used, which enables the measurement of the velocity of the particles through the center and some frontier regions of the studied spacer. As expected, it was possible to observe areas of recirculation, with a similar tendency to those obtained during simulation. The main difference relied on the absolute values of the velocity, which might be related to the lack of symmetry along the spacer and also probably due to the turbulent flow that probably exists inside the tube included in the mechanism used to simulate the respiratory system.