Chronic bronchitis overview

Overview
Bronchitis is an inflammation of the bronchi (medium-size airways) in the lungs. Acute bronchitis is usually caused by viruses or bacteria and may last several days or weeks. Chronic bronchitis is not necessarily caused by infection and is generally part of a syndrome called chronic obstructive pulmonary disease (COPD); it is defined clinically as a persistent cough that produces sputum (phlegm) and mucus, for at least three months in two consecutive years.

Historical perspective
The terms chronic bronchitis and emphysema were formally defined at the CIBA guest symposium of physicians in 1959. COPD has probably always existed but has been called by different names in the past. Bonet described a condition of “voluminous lungs” in 1679. Matthew Baillie illustrated an emphysematous lung in 1789 and described the destructive character of the condition. The term COPD was first used by William Briscoe in 1965 and has gradually overtaken other terms to become established today as the preferred name for this disease.

Pathophysiology
Chronic bronchitis is defined in clinical terms as a cough with sputum production on most days for 3 months of a year, for 2 consecutive years. . Chronic bronchitis is hallmarked by hyperplasia (increased number) and hypertrophy (increased size) of the goblet cells (mucous gland) of the airway, resulting in an increase in secretion of mucus which contributes to the airway obstruction. Microscopically there is infiltration of the airway walls with inflammatory cells, particularly neutrophils. Inflammation is followed by scarring and remodeling that thickens the walls resulting in narrowing of the small airway. Further progression leads to metaplasia (abnormal change in the tissue) and fibrosis (further thickening and scarring) of the lower airway. The consequence of these changes is a limitation of airflow. .

Epidemiology and demographics
COPD occurs in 34 out of 1000 greater than 65 years old. In England, an estimated 842,100 of 50 million people have a diagnosis of COPD; translating into approximately one person in 59 receiving a diagnosis of COPD at some point in their lives. In the most socioeconomically deprived parts of the country, one in 32 people were diagnosed with COPD, compared with one in 98 in the most affluent areas. In the United States, the prevalence of COPD is approximately 1 in 20 or 5%, totalling approximately 13.5 million people in USA, or possibly approximately 25 million people if undiagnosed cases are included.

Risk factors
Chronic obstructive pulmonary disease is a group of diseases characterized by the pathological limitation of airflow in the airway that is not fully reversible. A full comprehensive diagnosis is needed to eliminate related conditions and isolate the influence of lifestyle and behavior risk factors on condition outcome. Some common risk factors are cigarette smoking, occupational pollutants, air pollution and genetics. Other risk factors are increasing age, male gender, allergy, repeated airway infection.

Differential diagnosis
In clinical practice, COPD is defined by its characteristically low airflow on lung function tests. In contrast to asthma, this limitation is poorly reversible and usually gets progressively worse over time. It should be differentiated from certain conditions that have similar presentation for instance congestive heart failure, chronic asthma, bronchiectasis, and bronchiolitis obliterans.