DPI Andersen cascade impactor

The APSD measurement of DPIs is typically performed under the same conditions as DDU testing, however a Preseparator is typically interposed between the induction port and stage 0 of cascade impactor to capture the large, non-inhalable carrier particles, to prevent impactor over-loading (when using an NGI or ACI). As for delivered dose testing of DPIs, test flow rate is set on the basis of a 4 kPa pressure drop across the device, to approximate the mean patient inhalation flow rate achieved during clinical use.