The present study builds on earlier work conducted by the authors, who concluded that a high delivered dose (DD) was not necessarily indicative of a good quality aerosol; which was defined in the study as a high respirable delivered dose (RDD) and fine particle fraction (FPF). 1 The current study also aims to consider aerosol quality from a wider perspective, including not only the RDD but the non-RDD (NRDD). DD and mass median aerodynamic diameter were determined, in accordance with the methods described in CEN Standard EN 13544- 1, 2 and the RDD and NRDD were calculated from these values. The results generated were in agreement with previous studies, in that a high DD from a nebulizer was not an indicator of a high RDD. Extending the study to
include NRDD indicated that some nebulizers that provided a high DD and RDD, also had a high NRDD, and some nebulizers that gave a low DD, but a high RDD, had a low NRDD. Given that the NRDD is the mass of drug delivered to the patient in larger particles, which potentially impact in the oral cavity and throat, and may cause irritation to the patient, NRDD should be a measure of performance that is considered when comparing the quality of aerosol delivery from nebulizers.