Biomedical Engineering Reference
In-Depth Information
Fig. 10.45
Reduced NGI
GSK configuration (
From
[
46
]—
used with permission
)
a comparison between this abbreviated impactor system and that produced by
reducing the NGI (rNGI) to an abbreviated system [
46
].
This modification was undertaken by eliminating collection stages in the NGI so
that following the inlet, the coarse-fine size separation took place at the stage 2 loca-
tion as normal. However, the filter collection stage containing a bespoke filter was
relocated to a position directly above stage 3 (Fig.
10.45
), and the remaining stages
of the NGI were not used (see Sect.
10.7
). API was recovered by rinsing Stages 1
and 2 together (representing the
LPM
) and separately from the recovery of API
from the Stage 3 filter (representing the
SPM
, i.e., the fine particle mass <4.46
μ
m
aerodynamic diameter).
A DPI simultaneously delivering two components with different
MMAD
values
was used for this study and was tested at a nominal flow rate of 60 L/min with a 4-s
“inhalation” time. The FSI was operated with a 5
m insert. All three systems incor-
porated the same Copley vacuum pump with TPK flow controller. Similar to the
Pfizer group studies, a multichannel Inhalation Profile Recorder (GSK) was used to
record the pressure drop-elapsed time profiles via the connection of a pressure
transducer to a pressure tap located in the throat of the apparatus-on-test.
Values of
SPM
(here equivalent to
FPM
<4.51μm
) and
LPM
(equivalent to
FPM
>4.51μm
ex NGI and rNGI), each expressed as a percentage of the label-claim dose, from the
systems are summarized in Fig.
10.46
. SPM for the FSI was observed to be between
5% and 10% greater than the equivalent values obtained when either the standard or
reduced NGI systems were used. As expected, the converse was observed for the
CPM
>5.0μm
.
The pressure drop-elapsed time profiles for the three configurations (Fig.
10.47
)
were almost identical for both NGI and rNGI, as might be anticipated based on their
similar internal dead volumes. However, the air acceleration rate during start-up of
flow with the FSI was noticeably faster than for the other systems. Daniels and
μ
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