Chronic bronchitis
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 smokers 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 is 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. The excess mucus is produced by an increased number of goblet cells, and enlarged submucosal glands in response to long-term 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.
In addition, chronic inhalation of air pollution, or irritating fumes or dust from hazardous exposures in occupations such as coal mining, grain handling, textile manufacturing, livestock farming, and metal moulding may also be a risk factor for the development of chronic bronchitis. Bronchitis caused in this way is often referred to as industrial bronchitis, or occupational bronchitis. Rarely genetic factors also play a role.Air quality can also affect the respiratory system with higher levels of nitrogen dioxide and sulfur dioxide contributing to bronchial symptoms. Sulfur dioxide can cause inflammation which can aggravate chronic bronchitis and make infections more likely.Air pollution in the workplace is the cause of several non-communicable diseases (NCDs) including chronic bronchitis. Treatment
Decline in lung function in chronic bronchitis may be slowed by stopping smoking. Chronic bronchitis may be treated with a number of medications and occasionally oxygen therapy. Pulmonary rehabilitation may also be used.A distinction has been made between exacerbations (sudden worsenings) 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. Erdosteine is a mucolytic recommended by NICE.