Cough threshold in patients with chronic obstructive pulmonary disease.
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.
Wong
C H
CH
Department of Medicine, Northern General Hospital, Sheffield, UK.
Morice
A H
AH
D000328:Adult; D000368:Aged; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents; D003371:Cough / Q000209:etiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000150:complications* / Q000503:physiopathology; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D014797:Vital Capacity / Q000502:physiology
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride