Defining Subsets of Patients With Chronic Bronchitis

Abstract

Chronic bronchitis is defined by common consensus as daily production of sputum for at least 3 months in 2 consecutive years. The hypersecretion of mucus is a result of hypertrophy of submucosal glands and increased numbers of goblet cells in the epithelium. Mucociliary clearance is delayed due to excess mucus production and loss of ciliated cells, and this leads to a history of productive cough. 1 Wilson R Secondary ciliary dysfunction. Clin Sci. 1988; 75: 113-120 Crossref PubMed Scopus (28) Google Scholar Now that air quality has improved, cigarette smoking is the main etiologic agent; however, it is notable that in many studies, a minority of patients claim to be nonsmokers, yet have symptoms of chronic bronchitis without another obvious explanation. Patients with chronic bronchitis are a heterogeneous group owing to the range of severity of the condition and its common association with airflow obstruction, which may or may not be reversible, and emphysema. Three separate but overlapping entities have been defined: simple chronic bronchitis, chronic or recurrent mucopurulent bronchitis, and chronic obstructive bronchitis. 2 Medical Research CouncilDefinition and classification of chronic bronchitis for clinical and epidemiological purposes. Lancet. 1965; 1: 775-779 PubMed Google Scholar Acute exacerbations of chronic bronchitis (AECB) are common to all three groups, but their cause may be difficult to identify and might include viral infection, environmental pollutants, allergic responses, and bacterial infection. The cause of an exacerbation may be multifactorial, so that viral infection or levels of air pollution may exacerbate preexisting inflammation in the airways, which in turn may predispose to secondary bacterial infection. It is estimated that bacterial infection plays a part in between one half and two thirds of exacerbations. 3 Gump DW Phillips CA Forsyth BR et al. Role of infection in chronic bronchitis. Am Rev Respir Dis. 1976; 113: 465-473 PubMed Google Scholar , 4 Monso E Ruiz J Rosell A et al. Bacterial infection in chronic obstructive pulmonary disease: a study of stable and exacerbated outpatients using the protected specimen brush. Am J Respir Crit Care Med. 1995; 152: 1316-1320 Crossref PubMed Scopus (529) Google Scholar