Cough and its importance in COPD

Abstract

Patients with COPD most frequently complain of breathlessness and cough and these are both increased during exacerbations. Studies have generally focused on quality of life during end-stage disease, where breathlessness becomes dominant and cough less important. There are very little data on the frequency and severity of cough in COPD or its impact on quality of life at different stages of disease. Little is known about the factors that influence objective cough counts in COPD. Cough may be a marker for progressive disease in milder COPD patients who continue to smoke, and it may be useful in case-finding for milder disease in the community.The cough reflex sensitivity is heightened in COPD compared with healthy volunteers and similar to that in subjects with asthma. The degree of airflow obstruction does not predict cough reflex sensitivity or objective cough counts, implying an independent process. Effective treatments for cough in COPD have not yet been identified. Improved outcome measures of cough, a better understanding of cough in the natural history of COPD, and its importance to patients are needed.

Figure 1

Chance of having airflow obstruction with increasing age in smokers with or without cough (bars are 95% confidence intervals). Reprinted from Van Schayck CP, Loozen JM, Wagena E, et al. 2002. Detecting patients at a high risk of developing chronic obstructive pulmonary disease in general practice: cross sectional case finding study. BMJ, 324:1370–5. Copyright © 2002 with permission from BMJ Publishing Group.

Figure 2

Cumulative frequency at which subjects reached cough threshold (C5) for subjects with COPD and asthma compared with normal subjects. Reprinted from Doherty MJ, Mister R, Pearson MG. et al. 2000. Capsaicin responsiveness and cough in asthma and chronic obstructive pulmonary disease. Thorax, 55:643–9. Copyright © 2000 with permission from BMJ Publishing Group.

Figure 3

Scatter plot of relationship between cough threshold (C5) and FEV₁ for subjects with COPD and asthma Reprinted from Doherty MJ, Mister R, Pearson MG. et al. 2000. Capsaicin responsiveness and cough in asthma and chronic obstructive pulmonary disease. Thorax, 55:643–9. Copyright © 2000 with permission from BMJ Publishing Group.

Figure 4

Proportion of COPD subjects reporting chronic cough by final smoking status in A: subjects not reporting cough at start of study, B: subjects reporting cough at the start of the study. CS current smoker, IQ intermittent quitters and SQ sustained quitters. Reprinted from Kanner RE, Connett JE, Williams DE. et al. 1999. Effects of randomized assignment to a smoking cessation intervention and changes in smoking habits on respiratory symptoms in smokers with early chronic obstructive pulmonary disease: the Lung Health Study. Am J Med, 106:410–16. Copyright © 1999 with permission from Excerpta Medica, Inc.

Figure 5

Cough waveform patterns for (a) typical cough sound with a single explosive phase and (b) peel of cough sounds with multiple explosive phases.