Cough threshold in patients with chronic obstructive pulmonary disease
- aDepartment of Medicine, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK, bAcademic Department of Medicine, Castle Hill Hospital, Castle Road, Cottingham HU16 5JQ, UK
- Professor A H Morice.
- Received 11 May 1998
- Revision requested 13 July 1998
- Revised 2 September 1998
- Accepted 8 September 1998
Abstract
BACKGROUND Cough is an important symptom of patients with chronic obstructive pulmonary disease (COPD). The cough threshold to citric acid and capsaicin in patients with COPD and in normal volunteers was measured, as well as bronchial hyperresponsiveness to methacholine.
METHODS Nineteen patients with COPD and 22 controls were recruited. Subjects underwent a methacholine bronchoprovocation test and a cough challenge to citric acid and capsaicin.
RESULTS The log citric acid cough threshold D2 (concentration causing two coughs) was significantly lower in patients with COPD (mean 2.17 versus 2.56, mean difference (95% CI) 0.39 (0.04 to 0.74), p = 0.02) but not for capsaicin cough D2 (0.66 versus 0.8, p = 0.41). Sixteen patients with COPD had bronchial hyperresponsiveness which was correlated with baseline FEV1 (r= 0.6, p = 0.01, 95% CI 0.15 to 0.84).
CONCLUSIONS Patients with COPD have a lower cough threshold to citric acid, possibly due to a differential effect of cigarette smoke on citric acid sensitive cough receptors.
