Biomedical Engineering Reference
In-Depth Information
The shutter is set in the elevated (closed) position during connection of the VHC,
MDI actuation, and the subsequent delay period, but air can still be sampled by the
impactor at the desired flow rate via a bypass channel located on the side of the shut-
ter facing the induction port. A microphone (MIC) located on the adapter detects the
sound emitted at actuation of the MDI, starting a timer that operates a solenoid
valve immediately after the expiry of the selected delay period. This movement
retracts the shutter support pin, thereby permitting the shutter to drop, opening a
direct flow path from the VHC to the CI. The adapter introduces <5 ml additional
volume to the aerosol pathway from the VHC to the CI system. The “delay” appa-
ratus avoids the need to start the vacuum pump for the CI after the elapsed delay, a
situation that would result in undefined stage
d
50
sizes, while the flow rate is increas-
ing to its final stable value.
Although systems have been developed to enable a CI to be used in conjunction
with a breathing simulator [
68
-
70
], which would be the obvious extension of the
delay technique to mimic more closely tidal breathing, so far a standardized arrange-
ment has not yet been developed to the point at which it could be incorporated as
part of a compendial procedure for the evaluation of VHCs.
References
1. Hinds WC (1999) Aerosol technology: properties, behavior, and measurement of airborne
particles, 2nd edn. Wiley, New York, NY
2. Finlay WH (2001) The mechanics of inhaled pharmaceutical aerosols: an introduction.
Academic, London
3. Sbirlea-Apiou G, Katz I, Caillibotte G, Martonen T, Yang Y (2007) Deposition mechanics of
pharmaceutical particles in human airways. In: Hickey AJ (ed) Inhalation aerosols: physical
and biological basis for therapy. Informa Healthcare, New York, NY, pp 1-30
4. European Directorate for the Quality of Medicines and Healthcare (EDQM) (2012)
Preparations for inhalation: aerodynamic assessment of fine particles. Section 2.9.18—
European Pharmacopoeia [—Apparatus B in versions up to 4th edn. 2002] Council of Europe,
67075 Strasbourg, France
5. United States Pharmacopeial Convention (2012) USP 35-NF 30 Chapter 601: aerosols, nasal
sprays, metered-dose inhalers and dry powder inhalers. United States Pharmacopeial
Convention, Rockville, MD
6. European Medicines Agency (EMA) (2006) Guideline on the pharmaceutical quality of inha-
lation and nasal products (2006) EMEA/CHMP/QWP/49313/2005 Corr. 2006. London.
http://
WC500003568.pdf
. Visited 22 Aug 2011
7. United States Food and Drug Administration (FDA) (1998) Draft Guidance: Metered Dose
Inhaler (MDI) and Dry Powder Inhaler (DPI) Drug Products Chemistry, Manufacturing
and Controls Documentation. United States Federal Drug Administration, Rockville, MD.
Docket 98D-0997
http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatory
Information/Guidances/ucm070573.pdf
. Visited 22 Aug 2011
8. Mitchell JP, Bauer R, Lyapustina S, Tougas T, Glaab V (2011) Non-impactor-based methods
for sizing of aerosols emitted from orally inhaled and nasal drug products (OINDPs). AAPS
PharmSciTech 12(3):965-988
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