Alan P. McKiernan1, Treasa M. Thomas1 & Cathal Duignan1
1Prior PLM Medical, IDA Business & Technology Park, Carrick-on-Shannon, N41 WK46, Ireland
Summary
Background: With new regulations on the horizon, the industry is looking at switching inhaler propellants to greener alternatives. These new propellants may have different properties and so their effect on the dose delivery mechanics and fluid dynamics needs to be carefully studied.
Methods: We have used phase contrast X-ray imaging at a synchrotron to investigate the sump/orifice region of off-the-shelf pMDI actuators during dose release with HFA 134a and HFA152a propellants. We have used Schlieren imaging, an optical technique that is sensitive to refractive index gradients which are often present in pMDI plumes due to gas density variations, to have observe plume expansion up to 120 mm from the same commercial pMDIs.
Results: It was observed that HFA 152a drives marginally faster plumes than HFA134a despite a slightly lower vapour pressure. Propellant boiling/cavitation behaviour appears similar for both propellants. The liquid/gaseous spray cones from each type of propellant behave similarly.
Conclusions: While further investigations will certainly be undertaken by the industry in the coming years to evaluate through-life performance of shot-weight and particle size distribution, component compatibility etc. we have seen that the inhaler dose release dynamics are broadly similar between the two propellants in placebo form.
Key Message
The inhaler dose release dynamics are broadly similar between the HFA134a and HFA152a propellants in placebo form in commercial actuators which suggests that HFA152a may be a suitable greener alternative, notwithstanding other aspects of inhaler performance that need further exploration.