Variable airflow obstruction is a pathophysiological hallmark of asthma; however, the interactions between acute bronchoconstriction and the cough reflex are poorly understood. We performed a randomised, single-blind, placebo-controlled, crossover study to investigate the interaction between bronchoconstriction and cough in asthma. Capsaicin was administered to evoke coughs and methacholine to induce bronchoconstriction. We demonstrated that acute bronchoconstriction increased capsaicin-evoked coughs, which improved as airway calibre spontaneously resolved. However, capsaicin-evoked coughing had no impact on methacholine-induced bronchoconstriction. This study provides evidence that bronchoconstriction increases the activation of capsaicin-responsive airway nerves, but the precise mechanisms and mediators involved require further evaluation.
Trial registration number ISRCTN14900082.
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Contributors IS, HB, MW, PMO, SJF and JAS: concept and design. IS and HB: data generation. IS and JAS: statistical analysis and modelling. All authors reviewed the manuscript and approved the final draft.
Funding National Institute for Health Research, South Manchester Clinical Research Facility.
Competing interests JAS is a named inventor on a patent, owned by University Hospital of South Manchester, describing a method for generating output data licensed to Vitalograph; however, no financial benefits have been received.
Patient consent Obtained.
Ethics approval North West, Liverpool East Ethics Board (15/NW/0052).
Provenance and peer review Not commissioned; externally peer reviewed.
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