Biomedical Engineering Reference
In-Depth Information
Fig. 10.21
Westech Instrument Services fine particle dose impactor (FPD-AVCI). (
a
) External
appearance. (
b
) Cross-section through interior (
Courtesy of Westech Instrument Services Ltd.
)
to improve ease of use, notably a bayonet fixing between stages to allow rapid
assembly/disassembly of the CI. The replacement of the standard ACI collection
plates with glass or metal Petri dishes facilitates in situ recovery of API. The size-
separation stages themselves are based on stages 2 and 6 of the AVCI, having nomi-
nal jet diameters of 0.914 mm and 0.254 mm, respectively, with corresponding cut
points of 4.7 and 1.1
m aerodynamic diameter.
In 2010, Chambers and colleagues at AstraZeneca (AZ), UK undertook a perfor-
mance evaluation study of the FPD apparatus, comparing it against a 6-stage
nonviable ACI, and also a 2-stage abbreviated nonviable ACI (sACI) that utilized
ACI stages 2 and 5 with a blank stage 0 present (and was therefore equivalent to the
T-FSA/AIM-pHRT design), as benchmark systems [
32
]. Here the prefix “s” stands
for standard (i.e., nonviable ACI) components. The performance of the CIs was
assessed against the following metrics:
μ
1. Total mass [dose collected by impactor equivalent to impactor mass (
IM
)]
2. Mass of API collected by induction port (USP/Ph. Eur.) [equivalent to
nonimpactor-sized mass (
NISM
)]
3. Coarse particle mass >4.7
μ
m aerodynamic diameter (
CPM
>4.7μm
)
4. Fine particle mass <4.7
m aerodynamic diameter (
FPM
<4.7μm
)
5. Extra-fine mass collected on back-up filter (
EPM
<1.1μm
)
Three pMDIs containing a single component API were used to evaluate the per-
formance of the FPD-AVCI and sACI relative to data generated from the 6-stage
ACI. The collection plates of the 6-stage ACI were uncoated in accordance with
normal practice for working with this class of OIP. However, the respective plates
and Petri dishes of the sACI and FPD-AVCI were coated with a Brij 35-coating
solution based on the findings from the earlier work reported in Sect.
10.3
.
An additional experiment was carried out in order to investigate the extent of
possible particle re-entrainment whereby Brij-coated Westech filter papers were
placed on the plates and Petri dishes of both stages of the sACI and FPD-AVCI,
μ
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