Comprehensive Experimental and Numerical Studies of Pharmaceutical Aerosol Devices

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Pressurized metered-dose inhalers (pMDIs) or “puffers”, dry powder inhalers (DPIs), and nebulizers are normally used in the treatment of lung diseases, such as asthma and bronchitis. Statistics from Lung Associations indicate that up to approximately 10% of the population may suffer from respiratory illnesses requiring treatment in part of their lives. Inhaler devices produce very complex turbulent flows and ideal medication delivery remains a challenging engineering problem. Considerable amounts of aerosol medication generated from the pMDIs are deposited and lost on the walls of the upper airways (mouth-throat-trachea) before reaching the target (or the lungs), resulting in considerable medication losses from a single dosage (Fink, 2000). Add-on spacers (normally cylindrical chambers) are devices that are attached to the pMDIs and will enhance the total amount of medication delivered to the lungs. Besides medication delivery to the lungs, nasal drug delivery using pharmaceutical aerosols is emerging as an important alternative for treating many conditions such as diabetes (insulin delivery), osteoporosis, and even migraine headaches. Due to complexity of the nasal cavity and differences in regional medication absorptiveness, which is also affected by the medication properties (formulation and aerosol size distribution characteristics) and fluid flow structures, the ideal nasal drug delivery remains a challenging problem. In collaboration with the Ottawa Civic Hospital, we have been developing a novel and idealized nasal cavity geometry, which is a potential candidate to be used as a standard (for aerosol deposition measurements) in the pharmaceutical field. Despite the importance and growing interest in inhaled medications, research and development of pharmaceutical aerosol devices have focused more on therapeutical effectiveness. More efficient inhalation devices will reduce side effects (like muscle cramps and sore throat) and improve patients' compliance, thus reducing duration and costs of treatment. The present proposed research aims at the better understanding of the physics involved in aerosol drug delivery systems (both lung and nasal) and the improvement of the performance of inhalation devices in terms of maximizing medication delivery, through ongoing comprehensive studies of aerosol generation, transport, and deposition inside devices themselves and mainly in extra-thoracic airways (nose-mouth-throat), using experimental analysis (aerosol deposition and fluid flow measurements) and Computational Fluid Dynamics (CFD). The author also wishes to use similar approaches and expand the investigations towards the understanding (transport and extra-thoracic deposition mechanisms) and characterization of airborne allergic triggers with a focus on PM2.5 (particulate matter with diameter smaller than 2.5 microns), especially nanoparticles.