Abstracts from The Aerosol Society Drug Delivery to the Lungs 23Edinburgh International Conference CentreEdinburgh, Scotland, UKDecember 5–7, 2012

Background: In the adenosine 5'-monophosphate (AMP) bronchial challenge test, AMP is usually administered according to dosing protocols developed for histamine/methacholine. It has never been thoroughly investigated whether these protocols are suitable for AMP as well. Methods: The setup of the two-minute tidal breathing test was simulated in the lab with the APS Sidestream nebuliser. The procedure as described in the ATS guideline was followed. The influence of jet pressure, suction flow rate and AMP concentration on nebuliser output rate and droplet size distribution (measured by laser diffraction analysis) were determined. Results: The volume median diameter of the aerosol at a jet pressure of 1.5 bar (VMD 5.10 μm) was distinctly larger than the manufacturer's specifications (MMAD 3.2 μm). Reducing the jet pressure to obtain the output rate as specified by the ATS, increased the VMD to 8.49 μm. The output rate was increased when a suction flow rate was used to remove the aerosol. Increasing the AMP concentration did not have a clear effect on the output rate, but resulted in a shift of the droplet size distribution towards finer droplets. Conclusions: Increasing the AMP concentration has a dramatic effect on the droplet size distribution in the aerosol, and hence, on the site of deposition. The response may not depend on concentration alone. Therefore, nebulisation might not be a suitable administration method for AMP in bronchial challenge testing. Furthermore, specifying two or three parameters is not sufficient to standardise bronchial challenge testing, particularly when these parameters cannot be controlled independently