Aerodynamic particle size assessment

The two critical attributes characterizing the performance of DPIs are the imiformity of the delivered dose and the aerodynamie assessment of partiele size distribution. To determine the imiformity of the delivered dose, an apparatus capable of quantitatively retaining the dose leaving the deviee is used. For aerodynamic particle size assessment, a multistage liquid impinger or easeade impaetor is used. All aerosol performance testing must be condueted under defined temperature and humidity conditions. 

The various pharmacopoeias outline appropriate methods for aerodynamic assessment of particle size distribution. The USP defines the size distribution through mass median aerodynamic diameter (MM AD) and geometric standard deviation (GSD). None of the pharmacopoeias specify a requirement for particle size. However, the particle size specifications that are set should be appropriate for the intended use of the product. For example, if the particles are intended to reach the deep lung, the MMAD of particles exiting the... 

Quantitatively, the appropriateness of particles for pulmonary delivery is assessed by the aerodynamic diameter, a term developed by aerosol physicists which takes into account size, shape, and density, and is typically determined by an inertial sampling device such as a cascade impactor. The aerodynamic diameter, >aer (pm), for particlcs greater than 500 nm can be approximated by ... 

The subject of this particular volume relates to aerosol particle physics including aerosol characterisation, the formation mechanism, the aerodynamic size distribution of the activity and aerosol residence time, instrumentation techniques, aerosol collection and sampling, various kinds of environmental (atmospheric aerosols), particularly radioactive aerosols and the special case of radon decay product aerosols (indoors and outdoors) and the unattached fl ac-tion, thoron decay product aerosols, the deposition patterns of aerosol particles in the lung and the subsequent uptake into human subjects and risk assessment. 

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