Theoretical Basis for the EDA Concept - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 161

Table 7.2 Regression analysis and goodness-of-fit statistics for stage groupings versus MMAD

Coefficient
of determination,
R 2 (%)

OIP
filecode

Stage
grouping

RMSE/b
(μm) Product type Slope ( b ) RMSE

w9k201 HFA suspension MDI >9.0 22.1 4.69 48.2 0.212

9.0-4.7 12.3 1.28 79.4 0.104

4.7-2.1 −2.93 2.56 5.2 −0.874

<2.1 −2.81 0.986 25.5 −0.351

w9j901 HFA suspension MDI >9.0 3.25 5.72 0.5 1.760

9.0-3.3 8.57 0.624 74.5 0.073

3.3-1.1 11.3 3.55 13.6 0.314

<1.1 0.096 0.767 0.0 7.990

w9j801 HFA solution MDI >9.0 21.8 9.04 33.9 0.415

9.0-3.3 5.21 1.08 67.0 0.207

3.3-1.1 2.53 6.10 1.0 2.411

<1.1 −24.1 3.28 82.5 −0.136

w9jk01 DPI >8.6 −9.98 6.09 2.8 −0.610

8.6-4.4 8.58 0.733 59.2 0.085

4.4-1.1 13.1 4.42 8.5 0.337

<1.1 0.391 0.960 0.2 2.455

w9k901 DPI >8.6 0.990 5.85 0.2 5.909

8.6-4.4 18.0 1.43 91.8 0.079

4.4-1.1 −10.2 3.47 37.7 −0.340

<1.1 −1.34 0.43 13.4 −0.317

w9j601 CFC suspension MDI >9.0 2.02 8.93 0.1 4.421

9.0-4.7 2.30 0.376 50.1 0.163

4.7-1.1 0.09 4.03 0.0 44.778

<1.1 −1.71 0.413 31.5 −0.242

w9k001 CFC suspension MDI >10 11.3 3.78 12.0 0.335

10-4.7 14.9 1.52 59.4 0.102

4.7-2.1 −2.68 3.49 0.9 −1.302

<2.1 −9.54 1.02 57.1 −0.107

w9kw01 CFC suspension MDI >10 7.62 2.97 10.6 0.390

10-4.7 9.65 1.01 62.3 0.105

4.7-2.1 5.68 3.19 5.4 0.562

<2.1 −18.0 1.29 77.9 −0.072

particular data set. The RMSE/b values for both DPIs indicate that the LPM / SPM
ratio is about average in performance with respect to detecting changes in MMAD .
Based on these considerations, Tougas et al . came to the conclusion that the RMSE/b
statistic is believed to be the better predictor of the relative performance of the
LPM / SPM ratio among the product types surveyed.
In contrast, the performance of regressions of stage groupings versus MMAD
reported in Table 7.2 was significantly inferior with respect to this statistic. The results
in Table 7.2 are believed to reflect the performance of the current practice of construct-
ing stage groupings based on empirical inspection. Besides exhibiting inferior correlation