BioMedical Device Design Optimization

Metered dose inhalers (MDIs) are widely used for the treatment of lung diseases, such as asthma. The delivery of the drug to the lung can be as low as 5% of the metered dose. In order to maximize the dose, a patient needs to inhale whilst simultaneously actuating the inhaler, which can be difficult. Spacers have been developed to solve these drawbacks, and increase drug delivery to the lungs. However, there continues to be significant room for improvement.

FTS Engineering Answers has been investigating the parameters of most influence of drug delivery (the atomized droplet size distribution and the spacer geometry) using transient, multiphase CFD simulations.

The majority of the mass of the metered dose is an accelerant, typically HFA134, which provides the energy to atomize the spray. Detailed properties of the accelerant and the drug as well as multiphase heat and mass transfer are required in order to capture these physics correctly.

These physics are combined with detailed geometrical models of a range of spacer devices and design options (position of vents, valve position and design etc.) to quantify the effect of each change on the drug delivery.