Comparison of different nebulisation systems for capsaicin cough challenge testing

Cough challenge testing is an established research tool used to experimentally induce cough in humans for many decades [1]. During a cough challenge, tussive agents such as capsaicin, citric acid, and ATP are inhaled in increasing doses and the number of coughs evoked counted to provide a measure of sensitivity and responsiveness of the cough reflex [2, 3]. ERS guidelines for the assessment of cough (2007) recommended single-breath inhalation of tussive agents delivered using a dosimeter-controlled, air-driven nebuliser [4]. The incorporation of a regulator valve to limit inspiratory flow to 0.5 L·s−1 is also advised to ensure consistency, as variability in inspiratory flow affects aerosol particle deposition in the airways and thus cough responses [5, 6]. In recent years, the equipment commonly used for cough challenge testing, the Koko dosimeter (nSpire Health Ltd, UK) and characterised DeVilbiss 646 nebuliser (DeVilbiss Health Care Inc., US) have become irreparable and obsolete. The Provo.X (Ganshorn Medizin Electronic GmbH, Germany) is a possible suitable replacement provocation system for cough challenge testing but requires comparison with the established equipment. The aim of this study was to test and compare cough responses to capsaicin measured using the Provo.X and Koko dosimeters in a group of healthy volunteers. Capsaicin, the pungent extract of red chilli peppers, has been the most widely used agent to safely and reproducibly induce cough [3, 7]. Footnotes This manuscript has recently been accepted for publication in the ERJ Open Research . It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJOR online. Please open or download the PDF to view this article. Conflicts of interest: The VitaloJAK algorithm has been licensed by Manchester University Foundation Trust (MFT) and the University of Manchester to Vitalograph Ltd and Vitalograph Ireland (Ltd). MFT receives royalties which may be shared with the clinical division in which JAS works.