Chronic bronchitis is a lower respiratory tract disease, defined by a productive cough that lasts for three months or more per year for at least two years. The cough is sometimes referred to as a smoker’s cough since it often results from smoking. When chronic bronchitis occurs together with decreased airflow it is known as chronic obstructive pulmonary disease (COPD). Many people with chronic bronchitis have COPD however, most people with COPD do not also have chronic bronchitis. Estimates of the number of people with COPD who have chronic bronchitis are 7 to 40%. Estimates of the number of people who smoke and have chronic bronchitis who also have COPD is 60%.
The term “chronic bronchitis” was used in previous definitions of COPD but is no longer included in the definition. The term still used clinically. While both chronic bronchitis and emphysema are often associated with COPD, neither is needed to make the diagnosis. A Chinese consensus commented on symptomatic types of COPD that include chronic bronchitis with frequent exacerbations.
Chronic bronchitis is marked by mucus hypersecretion and mucins. Excess mucus results from an increase in goblet cells and enlarged submucosal glands due to prolonged irritation. The mucous glands in the submucosa secrete more than the goblet cells. Mucins thicken mucus, and their concentration has been found to be high in cases of chronic bronchitis, and also to correlate with the severity of the disease. Excess mucus can narrow the airways, thereby limiting airflow and accelerating the decline in lung function, and result in COPD. Excess mucus shows itself as a chronic productive cough and its severity and volume of sputum can fluctuate in periods of acute exacerbations. In COPD, those with the chronic bronchitis phenotype with associated chronic excess mucus, experience a worse quality of life than those without.
coughing helps clear the increased secretions. The cough often worsens upon waking, with the expelled mucus being yellow or green and sometimes containing blood. While coughing can effectively remove mucus at the start, excessive secretion buildup impairs clearance. When airways get blocked, coughing becomes less effective. Effective mucociliary clearance depends on airway hydration, ciliary beating, and the rates of mucin secretion. Each of these factors impaired in chronic bronchitis. Chronic bronchitis can lead to a higher number of exacerbations and a faster decline in lung function. The ICD-11 lists chronic bronchitis with emphysema (emphysematous bronchitis) as a “certain specified COPD”.
Decline in lung function in chronic bronchitis may slowed by stopping smoking. Chronic bronchitis may be treated with a number of medications and occasionally oxygen therapy (see oxygen therapy link here read more) with oxygen concentrator. Pulmonary rehabilitation may also be used.
A distinction has been made between exacerbations of chronic bronchitis, and otherwise stable chronic bronchitis. Stable chronic bronchitis can be defined as the normal definition of chronic bronchitis, plus the absence of an acute exacerbation in the previous four weeks. A Cochrane review found that mucolytics in chronic bronchitis may slightly decrease the chance of developing an exacerbation. The mucolytic guaifenesin is a safe and effective treatment for stable chronic bronchitis. This has an advantage in that it is available as an extended use tablet which lasts for twelve hours. In those with the chronic bronchitic phenotype of COPD, the phosphodiesterase-4 inhibitor roflumilast may decrease significant exacerbations.