Physical Causes of APSD Changes in Aerosols from OIPs and Their Impact on CI Measurements - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 55

Chapter 3
Physical Causes of APSD Changes
in Aerosols from OIPs and Their Impact
on CI Measurements

Helen Strickland, Beth Morgan, and Jolyon P. Mitchell

Abstract The successful implementation of AIM and/or EDA principles to the
in vitro assessment of inhalable aerosols emitted from OIPs requires the user of
such methods to have a basic understanding of how these particles and/or droplets
interact with the human respiratory tract (HRT) upon inhalation. Such processes are
inextricably governed by the underlying physical processes associated with these
semi-stable systems, and all of the changes influencing particle size affect the entire
APSD. This chapter looks at both aspects in some detail, in particular paying atten-
tion to how small changes in APSD might be detected by full-resolution CI systems.
The information presented herein is a prelude to Chap. 9 , in which case studies are
presented to demonstrate the sensitivity of EDA metrics to such changes.

3.1 Introduction

It is worthwhile briefly reviewing how aerosols are formed in the first place from the
different inhaler classes, before exploring the ways in which aerosols emitted by
OIPs are currently measured in the laboratory, and later in the topic, how the AIM
and related EDA concepts may make the process more efficient and effective in the