Application of synchrotron-based x-ray diagnostics for the investigation of pressurised metered-dose inhaler sprays

Despite the extended and widespread use of pressurised metered-dose inhalers (pMDIs) for the treatment of respiratory disease, much remains unknown about the processes that determine their performance. Synchrotron x-ray diagnostics developed for fuel spray research are applied for the first time to pMDIs. These data confirm a long-held belief that the pMDI spray is highly vaporised at the nozzle exit. X-ray visualisations reveal internal flow phenomena that provide an explanation for the greater spray stability of pMDIs that contain cosolvent. These data are used to advance thermodynamic models that are used to predict pMDI performance.