Thesis-2008-Davis.pdf (49.29 MB)
A fundamental study of the flow and droplet delivery from a pressurised metered dose inhaler (pMDI)
thesis
posted on 2013-04-30, 13:21 authored by A.J. DavisThe assessment of drug formulations delivered by the pressurised metered dose inhaler
and used in the treatment of Asthma are assessed commercially using cascade
impactors which are the preferred instruments for the assessment of particle size and
respirable mass or fraction delivered by inhalation devices. The fundamental principle
underpinning the design of cascade impactors is particle motion defined by Stokes
theory. The analysis of impactor data raises a number of functional issues as calibration
curves have long tails, which are not easily explained by a simplistic application of
Stokes law. The atomisation process, propellant flashing, evaporation and aerodynamic
properties of the residual drug particle detennine the distribution of the drug particles
within the lung and resultant therapeutic effect.
The research uses mathematical modelling and computational fluid dynamics (CFD) to
evaluate the flow and inertial deposition in the USP throat and the plates of the ACI
which is the most widely used cascade impactor. The CFD analysis shows the flow in
the outlet section of the USP throat to be unstable for the basic design, when coupled to
an outlet extension and when coupled to the ACI via the standard coupler and first jet
stage. The modelling also provides insight as to why the calibration curves of the ACI
have long tails and reveals a number of issues with the design of the ACI coupler and
the fundamental design of impactor jet arrays as well as the position and functional
response of upper impactor plates. Additional particle sizing methodologies were used
to assess the lognonnal characteristics of the atomised droplets and residual drug
particles. The experimental data was compared to current atomisation model and
modification recommended and a proposed alternative model with improved fit to the
data.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© A.J. DavisPublication date
2008Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.540809Language
- en