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

Spacers are typically used with pMDIs by patients suffering from chronic lower respiratory tract diseases such as asthma. Deposition of medication, salbutamol sulphate, was studied in a medium- and large- volume spacer, namely, the Volumatic™ and OptiChamber® spacer. Experiments were conducted at inspiratory flow rates ranging from 30 to 60 L/min, and deposition of medication in the spacers were assessed using spectrophotometry. Computational fluid dynamics was used to quantify the deposition (and its mechanism) numerically at 30 L/min. Medication deposition in the spacers was found to be greater in the lower half due to a downward spray angle. Additionally, it was determined more deposition of medication could be expected in the distal half of the spacers. An increase in flow rate demonstrated a minimal increase (2-3%) in the medication delivered to the inline filter. The numerical analysis demonstrated that turbulence effects are likely to cause deposition in both spacers.