Biomedical Engineering Reference
In-Depth Information
Fig. 10.33
FPF
<5.0μm
comparison by NGI and FSI from supplementary study investigating effect
of dry powder blending properties (
From
[
38
]—
courtesy of D. Russell-Graham
)
Table 10.13
Comparative measurement times (h) between FSI and NGI use in aerosol assessment
from 6-DPI replicate measurements (
From
[
38
]—
courtesy of D. Russell-Graham
)
Impactor
Experimental
Analysis
Data processing
Total
FSI
2.0
0.67
0.33
3.0
NGI
6.0
2.5
0.5
9.0
not yet fully optimized during this assessment, these findings would suggest that,
conservatively, time savings of more than 50% are easily achievable using abbrevi-
ated systems, a potentially massive gain in productivity.
This group has since extended their investigation of the FSI by comparing it with
the NGI across a range of drug products dispensed from different DPIs, exploring
the potential impact of differences in pressure drop profile experienced by the device
on the data obtained from the abbreviated and full-resolution impactors [
40
]. The
following conditions were evaluated:
1. Product (1) contained two dosage strengths of the same API, each evaluated at
60 L/min (Fig.
10.34a
).
2. Products (2) and (3) were each two-component combination DPIs, tested at 60
and 70 L/min, respectively (Fig.
10.34b, c
).
3. Product (4) was a DPI having a greater flow rate dependency on API APSD,
evaluated at 60 L/min by FSI and at 60 and 90 L/min by NGI (Fig.
10.34d
).
It was postulated that the difference in internal volume between the FSI and NGI
could cause differences in the pressure drop profile experienced by the product, by
varying the characteristics of the time-dependent flow which passes through the
impactor when the flow is initiated at the controller. The internal volume of the FSI
(estimated to be approx. 960 mL) is substantially smaller than that of the NGI which
is close to 1,940 mL, when the pre-separator is included [
41
].
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