Validating AIM-Based Instrumentation and Associated Measurement Techniques - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 315

Fig. 10.36 Expanded pressure drop time profiles at the start of measurement for DPI combina-
tions studied by Russell-Graham et al . ( From [ 40 ]— courtesy of D. Russell-Graham )

Direction of Flow Direction of Flow

Configuration A Configuration B

Fig. 10.37 Dead volume configurations used by Pantelides et al . : (A) rapid expansion of flow and
(B) more gradual expansion of flow ( From [ 42 ]— used with permission )

order to simulate rapid expansion of flow (configuration A) and more gradual
expansion (configuration B) [ 42 ]. These vessels were located between the FSI and
switching valve (Fig. 10.38 ).
Additionally, the FSI was tested locating a standard NGI pre-separator prior to
the modified fine-cut pre-separator stage. Pressure drop profiles were recorded via a
pressure tap at the DPI mouthpiece using an inhalation profile recorder similar to
the method described by Burnell et al. [ 43 ].
The base of the coarse particle collector of the FSI was coated with silicone oil
to mitigate particle bounce and re-entrainment as described previously for the work
performed with the FSI by this group. The pressure drop profiles for the NGI, FSI,
and modified FSI configurations are shown in Fig. 10.39 .
The flow initiation portions are superficially similar to those illustrated in
Fig. 10.35 , taken from the previous study by this Pfizer (UK) group. The new data
showed a consistent trend of slowed pressure ramp (acceleration) rate with increas-
ing impactor dead volume in the order FSI (1,045 mL with USP/Ph. Eur. induction
port), FSI +500 mL Configuration A, NGI (2,025 mL with pre-separator and USP/