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Introduction Cough challenge testing is used to study cough mechanisms. Cough responses are quantified by counting the maximum number of coughs evoked by increasing doses of inhaled tussive agents (Emax), the concentration of tussive agent evoking 50% of the maximum response or the concentration evoking 2 or 5 coughs (C2, C5). In recent years, the equipment used for cough challenge, 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 potential replacement but requires comparison with established equipment. This study compared cough responses to citric acid using both devices and supplementing previous work for capsaicin cough challenge.Methods Healthy adults attended two visits, were naïve to performing cough challenge and had normal spirometry. At visit 1, consented participants performed spirometry and citric acid cough challenge delivered by either the KoKo or Provo.X system (order randomised). Four single inhalations of doubling concentrations of citric acid (0.03–4.0M) were administered every 30 seconds, and the number of coughs evoked within 15 seconds recorded. The challenge ended when the maximum tolerated dose was reached or all concentrations inhaled. At visit 2, the alternative nebuliser system was used. A flow regulator valve (modified duckbill valve, Vernay Laboratories) was incorporated into the Provo.X nebuliser to limit inspiratory flow to 0.5L/s.Results Twelve healthy volunteers were studied; 6(50%) males, median age 39(range 22–84), median(IQR) BMI 23.4(21.4–25.1), FEV1 and FVC%predicted 113%(100–122) and 120%(103–129) respectively.Cough responses for the Provo X vs. KoKo were median(IQR) Emax 12.0(8.3–14.8) vs. 10.5(5.3–17.8) coughs, ED50 1.0M(0.625–2.0) vs. 1.0M(0.3125–2.0), C2 0.5M(0.25–1.0) vs 0.25M(0.156–1.75). In 16/24 challenges C5 was not reached.Agreement between cough responses for the devices was Emax (intraclass correlation coefficient, ICC=0.87, p=0.001), ED50 (logED50 ICC=0.554, p=0.098) and C2 (logC2 ICC=0.51, p=0.135). There were no significant differences between cough responses across the range of concentrations from the two devices using GEE modelling, (p=0.393).Conclusions Based on the minimal differences observed between the devices, the Provo.X appears to be a suitable and comparable system for performing citric cough challenge.