A description of cough in tuberculosis and other respiratory conditions

Abstract

Cough is common but has been under-researched. In tuberculosis cough is probably of particular relevance in transmitting infection. This thesis explores several interlinking areas. Regarding how best to measure cough, coughs are shown to be recognizable to the human ear, but automated cough monitors can disagree with auditory cough counting. A novel approach to testing cough reflex sensitivity is described, E62.5. There was no evidence to support the hypothesis that cough has unique characteristics in tuberculosis, in terms of symptoms, frequency and clustering. A significant reduction of cough frequency in tuberculosis is demonstrated overnight. Clinical correlates of 24hour cough frequency were explored; female sex in unexplained chronic cough, and sputum smear status in tuberculosis were important, and possibly transfer factor in pulmonary fibrosis and duration of symptoms prior to treatment in COPD exacerbations. Cough frequency correlated poorly with symptoms. There seem to be both generic and disease-specific mechanisms associated with cough. This was further suggested by a faster reduction in cough frequency with treatment in pneumonia than in acute asthma and COPD exacerbations, correlating with C-reactive protein decline only in pneumonia. A serial reduction in 24-hour cough frequency in tuberculosis during the whole course of treatment was demonstrated, a potentially novel approach to measuring treatment response. The role of genetic polymorphism in the cough receptor gene TRPV1 was explored, but, at least in chronic cough was not demonstrated to predict coughing. Regarding the infectiousness of coughs, an airborne particle counter was shown not to be sensitive enough for measuring droplets released during coughing in room air. However, I demonstrate for the first time a significant association between 24-hour cough frequency in TB and household infection. This work has set a foundation for the further investigation of the mechanisms, processes and patterns of coughing with respect to tuberculosis transmission and other contexts.