Biomedical Engineering Reference
In-Depth Information
Fig. 1.2
Hypothetical full-resolution CI measurement system (
top
) compared with a 2-stage AIM
confi guration having cut-points with
d
ae
values close to 1
µ
m to provide discrimination of extra-
fi ne from fi ne particles and 5
m to separate fi ne from coarse particles (
bottom
); the symbols “F”
and “A” on the stages identify full-resolution and abbreviated CI confi gurations, respectively
µ
add-on devices, in particular spacers and valved holding chambers (VHCs) that are
frequently prescribed for use with MDIs [
10
].
Other enhancements include incorporation of one or more “dummy” stages not
containing a collection surface before the fi rst size-separating stage in order to
increase the internal dead space within the abbreviated impactor to be closer to that
of the full-resolution system. This measure can be important if low-volatile sub-
stances, such as ethanol, are present in the formulation being aerosolized. The vari-
ous AIM-based options that have been tried with different OIPs are examined in
Chap.
10
.
The EDA concept was developed in parallel with the AIM concept, with the
purpose of providing a more discriminating set of APSD-related metrics than the
so-called stage groupings, which relate to the mass of API recovered from all com-
ponents of a full-resolution CI and grouped, typically into three or four adjacent size
ranges (Fig.
1.3
) [
11
]. EDA is not intended to be a replacement for existing CI data
analysis procedures, such as the determination of fi ne particle mass (
FPM
) <5
m
in aerodynamic diameter, or the grouping of adjacent stages in a given CI to form a
reduced number of measures that can be related to likely deposition locations in the
respiratory tract. However, it will be shown explicitly in Chaps.
7
and
8
of the topic
that EDA does have the capability to be more discriminating of movements of the
aerosol APSD than these other techniques of data analysis.
µ
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