Theoretical Basis for the EDA Concept - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 154

lower
size
limit

upper
size
limit

lower
size
limit

upper
size
limit

aerodynamic diameter ( m m) aerodynamic diameter ( m m)

Nominal APSD Change in Area

lower
size
limit

upper
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limit

lower
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limit

upper
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aerodynamic diameter ( m m) aerodynamic diameter ( m m)

Change in Mean Change in Mean & Area

Fig. 7.6 Possible variation types in a unimodal OIP APSD

The ratio metric, large to small particle mass ( LPM / SPM ) is highly correlated with
the mass-weighted mean of the APSD (represented customarily by its MMAD ), but
independent of the area of the APSD, defined by the AUC (Chap. 1 ) [ 11 ]. The sec-
ond metric, impactor-sized mass ( ISM ) is related to the area defined by the APSD
when expressed in differential mass-weighted format, but independent of the
mean of the distribution [ 11 ]. Both metrics can be readily obtained directly either
from full resolution or abbreviated CI measurements (the latter is discussed in
Chap. 5 ) .
In order to characterize the performance of EDA, the CI-WG has utilized CI data
from marketed OIPs previously gathered by the parent IPAC-RS organization into a
blinded database, employing two fundamental statistical approaches in its assess-
ment: measurement system analysis (MSA) and operating characteristic curves
(OCCs). Background information on measurement processes and these two statisti-
cal approaches is provided here in order to aid the reader in understanding the theo-
retical principles that underlie EDA, before assessing the subsequent material that is
presented in Chap. 8 .