Nebulizers such as, Dry Powder Inhalers (DPI’s) and pressurized Metered-Dose Inhalers (pMDI’s), are all equally used in the treatment of asthma. For children, where the asthma incidence is high and where a good coordination between the device actuation and the respiration is needed to use the pMDI, a solution was found with the introduction of an add-on spacer to the pMDI. Because spacers attached to the pMDI are the cheapest and most efficient way to treat asthma in children, it is of the greatest relevance to improve its efficiency. This project, which concerns the study of the spacer geometry, is focused in the study, design and development of new valve geometries to enable a better delivery of the drug to the patient. This study was carried out using the Fluent™ software, from ANSYS. Once the input parameters and models were defined in order to get a realistic computational model, the geometry was optimized. This optimal solution was tested, compared and analyzed against Volumatic® valve, the spacer most widely used in the world. All the models, as well as the results obtained will be analyzed and discussed throughout the paper. It was concluded that some simple modifications, introduced on the shape of the cross-section of the valve geometry, yields radical changes in the air flow behavior. Optimizing the airflow by changing the geometry, reducing the vortex areas, will lower the waste of drug in the spacer, increasing the amount of delivery to the lung.
Pressurised metered dose inhalers with spacers versus nebulisers for -agonist delivery in acute asthma in children in the emergency department