Metered-dose inhaler efficiency enhancement: a case study and novel design.

The efficiency of the metered-dose inhaler (MDI) is a critical issue in aerosol medicine because it deals with delivering a life-saving medication to patients with various lung diseases. Mouthpiece diameter, air flow rate, and entrance angle are among many parameters that influence the MDI penetration efficiency. It is well known that inertial impaction accounts for the massive aerosol deposition in the oral airway. In this study, the authors present a novel simple modification of the inhaler mouthpiece using a wire-based jet depressor to reduce the inertial impaction of aerosols. A 0.5 mm diameter wire is placed inside the MDI mouthpiece at a distance of 2 mm in front of the MDI nozzle. Two mouthpieces were modified and employed in the experiments (16 and 20 mm). The penetration efficiencies are measured and the results of the modified mouthpiece are compared with the conventional mouthpiece. The experiments are conducted at three different air flow rates (30, 60, and 90 L/min) and five entrance/spray angles (0 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees). The results show that the new modified mouthpiece has higher aerosol penetration efficiency than the ones with the conventional mouthpiece. A second type of experiment is conducted to evaluate the relative strength of the aerosol impaction.