Time resolved measurement of the size distribution of pharmaceutical aerosols under realistic respiratory conditions

The most frequently used medications commonly applied during the therapy of human airway diseases are the inhalation medicines and systems that can introduce the active substances directly into the respiratory system. Determination of the deposition properties of aerosol medications is of particularly great importance during their development and approval, where the delivery of the proper dose to the targeted area and the overdose has to be controlled precisely. The size distribution and the delivered dose of pharmaceutical aerosols are commonly determined by cascade impactors, however optical particle spectrometry were also introduced recently as an alternative method (Kuhli et al., 2010). Optical particle counters determine optical or aerodynamic size distribution of aerosols based on elastic light scattering from individual particles passing their sensing volume. The advantage of this method compared to the gravimetrical measurements is its temporal resolution.