The effect of pH on citric acid cough challenge: A randomised control trial in chronic cough and healthy volunteers

Rai, Z. L.; Fowles, H. E.; Wright, C.; Howard, Joseph; Morice, A. H.

Abstract

© 2018 Elsevier B.V. Introduction: Citric acid has been used for over six decades to induce cough; however the mechanism of its pro-tussive effect is still not fully understood. We assessed the response to inhalation of citric acid at varying levels of acidity to determine if the pH of the solution plays a role in the induction of cough. Data was collected from both healthy volunteers and patients with chronic cough. Methods: 20 chronic cough patients and 20 healthy volunteers were recruited and underwent three cough challenges on separate days. Each visit involved 5 repeated one second inhalations of 300 mM citric acid solution. The concentration of the citrate cation remained constant, but the pH of the solution altered by the addition of sodium bicarbonate to 3, 5 and 6, representing the pKa values of the individual acid moieties. The total number of coughs elicited was recorded for each inhalation. Results: Two subjects withdrew and were not included in the analysis. Participants were gender matched, each group consisting of 12 females. 74% of chronic coughers coughed at pH 3 (mean coughs 16), 89% coughed at pH 5 (18) and 63% coughed at pH 6 (7). In healthy volunteers, 60% of subjects coughed at pH 3 (9), 30% of subjects coughed at pH 5 (3), and 10% of subjects coughed at pH 6 (0). Thus chronic cough patients coughed more than healthy volunteers and did not exhibit a clear pH concentration response. There was also a greater variability in their response to individual challenges.

Citation

Rai, Z. L., Fowles, H. E., Wright, C., Howard, J., & Morice, A. H. (2018). The effect of pH on citric acid cough challenge: A randomised control trial in chronic cough and healthy volunteers. Respiratory Physiology and Neurobiology, 257, 51-54. https://doi.org/10.1016/j.resp.2018.02.013

• Journal Article Type: Article
• Acceptance Date: Feb 21, 2018
• Online Publication Date: Mar 6, 2018
• Publication Date: 2018-11
• Deposit Date: May 10, 2022
• Journal: Respiratory Physiology and Neurobiology
• Print ISSN: 1569-9048
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 257
• Pages: 51-54
• DOI: https://doi.org/10.1016/j.resp.2018.02.013
• Keywords: Chronic cough; Cough challenge; Cough
• Public URL: https://hull-repository.worktribe.com/output/3609681