Capsaicin cough sensitivity in bronchiectasis

Background: Bronchiectasis is a suppurative airway disease characterised by persistent cough and sputum production associated with bronchial dilatation. A study was undertaken to determine whether cough sensitivity is increased in bronchiectatic patients. Methods: Twenty two patients with bronchiectasis and 20 healthy non-smoking controls matched for age and sex were recruited into the study. Quality of life ( Leicester Cough Questionnaire score), total cough symptom score, and extent of bronchiectasis on HRCT scans were recorded. Cough sensitivity was assessed using incremental inhalation of capsaicin concentrations; the concentration at which 5 or more coughs occurred (C5) was recorded. Results: Patients with bronchiectasis had increased sensitivity to capsaicin compared with controls ( mean ( SE) log(10) C5 1.22 (0.20) v 1.89 (0.21); p < 0.03). Capsaicin sensitivity correlated positively with the Leicester Cough Questionnaire score (r = 0.64; p = 0.005) and inversely with the total cough symptom score ( r = 20.58; p = 0.004), but not with the extent of the disease. It also correlated with forced expiratory volume in 1 second ( FEV1) in litres ( r = 0.58; p = 0.005) but not with FEV1 % predicted. Capsaicin sensitivity was not related to the presence of infected sputum or to corticosteroid or bronchodilator use. Conclusions : Patients with bronchiectasis have a sensitive cough reflex which reflects the severity of cough symptoms. A measure of cough severity could be part of health assessment for patients with bronchiectasis.