Pressurized Metered-Dose (pMDI) Aerosol Spray Deposition in Large-and Medium-Volume Spacers

Spacers (or holding chambers) are typically used with pressurized metered-dose inhalers (pMDIs) by patients suffering from chronic lower respiratory tract diseases such as asthma and chronic obstructive pulmonary disease (COPD).Attachments such as spacers provide a number of benefits including: a reduction of the "Cold Freon effect 1 ", better coordination (between pMDI actuation and inhalation), and a reduction of the inertial impaction of the medication in the oropharyngeal tract and oropharynx.These factors improve the inhalation of medication resulting in a larger percentage of medication delivered to the lungs when using a spacer device.However, spacer devices can also cause a loss of medication delivered by the pMDI due to deposition of the medication on the walls of the spacer itself.As such, it is important to understand the mechanisms which cause this medication loss to allow for future spacer devices to be designed more efficiently.Regional deposition of the medication, salbutamol sulphate, was studied in a medium-and large-volume spacer, namely, the Volumatic™ and OptiChamber® spacer.This study was completed using both experimental and numerical analyses.Experiments were conducted at typical inspiratory flow rates ranging from 30 to 60 L/min, which were typical for medication delivery.The amount of deposition of medication in the spacer device was assessed using spectrophotometry.Computational fluid dynamics (CFD) was also used to allow the implementation of particle tracking and quantify the 1 It should be noted that chlorofluorocarbons (CFCs) are no longer used in pMDIs and, as such, Freon is no longer present in the inhalers.However, the concept of a cold plume impacting the back of the throat (which was described by the Cold Freon effect) is still present in pMDIs even with current propellants.iii deposition (and its mechanism) numerically at a flow rate of 30 L/min.Simulations used both mean flow and turbulent particle tracking, applying unsteady Reynolds-averaged Navier-Stokes (URANS) equations with a shear stress transport (SST) turbulence model.Deposition of salbutamol sulphate in the Volumatic™ and OptiChamber® spacers was found to be greater in the lower half as opposed to the upper half of the spacer due to a downward spray angle.Additionally, it was determined more deposition of medication could be expected in the distal half of the spacer as opposed to the proximal half.An increase in flow rate demonstrated a minimal increase in the medication delivered to the inline filter which was analogous to that reaching the patient.The numerical analysis demonstrated that turbulence effects are likely to cause deposition in both the Volumatic™ and OptiChamber® spacer.Results suggested that a larger flow rate does not necessarily allow for more medication to be delivered, it acts only to shift the region of the deposition.As such, it is conjectured that each spacer should have an optimal flow rate as to where the most medication will be delivered without excessive inhalation by the patient.I would like to express my sincerest gratitude to my thesis supervisor, Professor Edgar Matida, for all the support, guidance and encouragement provided throughout my studies, during both my undergraduate and graduate research.I always appreciated your patient approach and positive attitude throughout my academic journey.This gratitude is extended to my colleagues as well, providing me clarity in times of stress, always willing to lend a helping hand and to listen whenever I needed a voice of reason.At home, I would like to thank my partner, as without her encouragement, and her never-ending love and support, I would not be where I am today.Your grace and passion mean the world to me.To my parents and brother, as well, who supported my education, encouraged me to be my best and were always there with advice and a home cooked meal whenever I needed to vent.I am sure, Mom, you would be happy to hear I am finally done!To my partner's family, who were always so understanding and caring.You are a wonderful bunch, bringing so much positivity and kindness (and great food!) to my life.Lastly

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