Spray pattern analysis for metered dose inhalers: effect of actuator design.

PURPOSE

This study was conducted to identify the device factors influencing spray pattern and particle size to gain a more complete understanding of spray plume measurements.

METHODS

A statistically designed experiment was used to investigate the influence of three actuator features (orifice diameter, expansion chamber depth, and orifice length) on spray pattern and particle size profiles. Custom-built actuators were manufactured and analyzed with laser light sheet illumination methods for spray patterns and laser diffraction for particle size analysis.

RESULTS

In addition to orifice size, spray patterns were significantly influenced by the actuator orifice length and sump depth. Particle size analysis of the plumes generated from actuators used in these studies showed that all actuator features (orifice size, length, and sump depth) were significant factors influencing particle size.

CONCLUSIONS

The performance of propellant-based metered dose inhaler aerosols seems to be significantly related to sump depth and orifice length, in addition to orifice size. Rational design of propellant-based metered dose inhalers should therefore consider these variables in addition to formulation strategies and simply modifying orifice diameter.