Chronic bronchitis refers to inflammation and infection of the bronchial tubes and mucosal membranes, generating an overproduction of mucus. The excessive production of mucus at the level of the respiratory tract is the body's inflammatory response to irritation and infection of the bronchia. Excess mucus perturbs the process of respiration by reducing the amount of air that is normally received by the lungs. Common symptoms of chronic bronchitis are: mucus-producing cough, difficult breathing, shortness of breath, chest pain and discomfort and wheezing.

Chronic bronchitis generates recurrent, time-persistent symptoms that intensify as the disease progresses. The main characteristics of chronic bronchitis are productive cough, increased susceptibility to bacterial and viral infections of the respiratory tract and low responsiveness to medical treatments. Chronic bronchitis usually lasts for up to three months and regularly reoccurs over the period of two years or more. In present, there is no specific cure for chronic bronchitis.

Unlike patients who suffer from acute bronchitis, patients with chronic forms of the disease don't respond well to treatments with antibiotics. The excessive production of mucus at the level of the bronchial tubes facilitates the proliferation of bacteria and other infectious organisms, thus contributing to the progression of the disease. On the premises of repeated infections and compromised natural defenses of the respiratory system (cilia barriers), antibiotics are often ineffective in completely overcoming chronic bronchitis. Thus, the treatment of chronic bronchitis is focused towards relieving the already existent symptoms and preventing the development of further complications.

In the incipient stages of the disease, the symptoms of chronic bronchitis are usually perceived in the morning or during the night. In more advanced stages of chronic bronchitis, the entire respiratory tract becomes inflamed and obstructed with mucus, generating intense, persistent cough. This type of recurrent, highly productive cough is commonly referred to as ?the smoker's cough?. As the disease progresses, chronic bronchitis sufferers also experience pulmonary problems and they are at risk of developing serious lung diseases (pneumonia, emphysema). In time, people with chronic bronchitis may suffer from poor oxygenation of the blood and hypoventilation (shallow, accelerated breathing). Complicated forms of chronic bronchitis may also involve cyanosis as a result of poor oxygenation of the lungs. Cyanosis (bluish aspect of the skin) generally suggests the presence of emphysema or pneumonia.

Although smoking alone can't be considered to be the cause of chronic bronchitis, the disease has the highest incidence in regular smokers. Smoking greatly contributes to the proliferation of bacteria and slows down the healing of the respiratory tissues and organs. Chronic bronchitis is often associated with asthma as well. Patients with chronic bronchitis who also suffer from asthma are even less responsive to specific treatments and they commonly experience symptomatic relapse. Sometimes, chronic bronchitis can be the consequence of untreated or mistreated acute bronchitis or other respiratory diseases. Chronic forms of bronchitis can also be developed by people who regularly expose themselves to airborne irritants such as dust, chemicals and pollutants.