Non-Symmetrical pMDI Deposition Measurement in Add-on Spacers

Gamal Alhegagi (1), Edgar Matida (1)

(1) Carleton University, Ottawa, Canada

     Abstract Number: 468
     Last modified: May 12, 2010

Abstract
Incoordination of actuation-inhalation is one of the main problems facing patients (especially elderly and young children) using pressurized metered-dose inhaler (pMDI) in the symptomatic treatment of certain respiratory diseases such as asthma and chronic bronchitis. Incoordination causes most of the inhaled drug to be deposited outside of the lower respiratory tract. Add-on spacers are simple volume holding chambers that are attached to the pMDI to enhance deposition of the inhaled drug into the lower respiratory tract where it produces its desired therapeutic effect.
In-vitro deposition of the short acting beta$_2 adenoceptor agonist Salbutamol Sulfate (Ventolin HFA$^(TM)) in three types of add-on spacers were studied experimentally at steady inspiratory flow rates of 30, 45, and 60 L/min, respectively. The add-on spacers include a relatively large volume (218 mL) valved add-on spacer, the OptiChamber$^((R)), a medium volume (110 mL) valved add-on spacer, the PocketChamber$^(TM), and a small volume (70 mL) non-valved add-on spacer, the OptiHaler$^((R)). The deposition of Salbutamol Sulfate was determined spectrophotometrically. Separate PIV investigations indicated that the spray angle deflected downwards (up to six degrees) and then upwards (back to zero degrees) during the actuation period (100 ms). It was conjectured that pMDIs would produce a non-symmetrical aerosol deposition in add-on spacer. The add-on spacer (OptiChamber$^((R)) was then split horizontally in half and Salbutamol Sulfate deposition was determined at the two different halves (upper and lower) at similar inspiratory flow rates.
Experimental results indicated that Salbutamol Sulfate deposition in the respiratory tract was higher in the large volume OptiChamber$^((R)) than in the medium and smaller volumes PocketChamber$^(TM) and OptiHaler$^((R)), respectively, in all inspiratory flow rates used. Aerosol spray from pMDI produced a higher Salbutamol Sulfate deposition in the lower half of the OptiChamber$^((R)) compared to the upper half in all inspiratory flow rates tested.