Chronic bronchitis is generally characterized by coughing, especially if coughing up phlegm, for at least three months, two years in a row. The duration of this illness is the main difference between it and acute bronchitis.
Chronic bronchitis and inflammation
Chronic inflammation of the bronchi, with the production of mucus or phlegm, leads to changes in the lining of the airways. The changes mainly affect the cilia, which are hair-like structures in the lining cells, and eventually the inflammation leads to the loss of ciliated cells. These ciliated cells have the job of clearing the airways from secretions and tiny dirt particles. As they are lost, their function is replaced by goblet cells. Goblet cells, in turn, secrete the mucus into the airways, creating a warm and moist environment that is very favorable for the bacteria to grow.
Secretions, swelling and inflammation block the normal airflow through and from the alveoli as they obstruct the bronchi and the bronchioles. This irritation causes the muscle surrounding the airways to contract, which is called bronchospasm.
Coughing, which is typical for chronic bronchitis, is the result of the body’s attempt to open and clear the airways.
Other than coughing, usually with clear, yellowish, brownish or green mucus, the symptoms of chronic bronchitis include pressure or pain in the chest, fatigue, shortness of breath, rapid breathing and wheezing.
Causes of chronic bronchitis
There are many possible causes of chronic bronchitis but the factor that is most commonly responsible for it is cigarette smoking. It is estimated that in the United States 49% of all smokers develop chronic bronchitis and 24% of them suffer from emphysema or chronic obstructive pulmonary disease. Some studies have found that as much as 90% of all cases of chronic bronchitis are cause by cigarette smoke, one way or another. Exposure to second-hand smoke is also a significant risk factor for chronic bronchitis.
Other inhaled irritants may also be responsible for it, such as smog, industrial pollution, solvents, airborne chemicals, aerosol sprays and such.
Frequent vital infections of the respiratory tract, as well as bacterial infections that have not been cured completely may also lead to chronic bronchitis. People who frequently suffer from acute bronchitis are at higher risk of developing the chronic form of this disease.
Allergies and asthma may also be responsible for chronic bronchitis, and so can other underlying diseases, such as cystic fibrosis, congestive heart failure and immunodeficiency.
Risk factors for chronic bronchitis, other than smoking, include exposure to pollution, acid reflux or GERD and frequent lung infections.