Cough in Health and Disease

Cough is a common symptom of both acute and chronic respiratory illness. It is poorly understood and treatment options are sparse. One reason is that there are few validated objective measures of cough frequency and severity. In this thesis I have further validated the Leicester Cough Monitor, an automated cough detection system capable of detecting coughs over 24 hours. I have demonstrated that automated cough numbers were similar to those derived from the gold standard of manual counting in healthy adults and in patients with respiratory disease. Cough frequency was then measured using the Leicester Cough Monitor and was almost 16 fold higher in patients with respiratory diseases compared to healthy controls. In the population as a whole there was a correlation between cough frequency and the induced sputum neutrophil count. I then conducted a randomised, placebo controlled, double blind, parallel group trial of low dose erythromycin taken daily for 3 months in 30 patients with unexplained chronic cough. Active treatment was associated with a reduction in the sputum neutrophil count but no difference in cough counts or other measures of cough severity. Also, there is no information on the natural history of unexplained chronic cough. In a longitudinal study of 42 patients with unexplained chronic cough followed up for at least 7 years, I found that cough, measure by the cough visual analogue score, improved in 25 percent. Unexpectedly, patients had an abnormally rapid fall in FEV1, whether cough improved or not. Finally, the assessment of health related quality of life is important in people with acute cough in order to evaluate potential therapies. I have shown that that the minimal important clinical difference in the Leicester Cough Questionnaire for those with acute cough is 2.5 and this will aid in the interpretation of treatment trials.