Dictionary of Allergies .. Chronic bronchitis

Chronic bronchitis

Chronic bronchitis remains a common cause of morbidity and mortality, and the cost to the nations due to lost working days and to health services is enormous. Cigarette smoking is the major etiologic factor, although exacerbations may be caused by viruses, environmental pollutants, allergic responses, and bacterial infections. New insights into the underlying basic mechanisms of bronchial inflammation are being made. Antibiotics are commonly used to treat exacerbations, although evidence of efficacy is sometimes lacking. Some patients may be prone to recurrent exacerbations and this influences their chance of recovery. Clinical trials must include an assessment of the severity of the exacerbation, and protocols would be improved by increased definition of the type of patient being enrolled and by inclusion of more detailed measures of benefit. Influenza and pneumococcal vaccination should be encouraged in appropriate patients [1].

The patient with bronchitis frequently experiences a productive cough on arising in the morning while the nights are relatively undisturbed unless gastroesophageal reflux and aspiration are present. It must distinguished from asthma which typically is characterized by variable breathlessness, wheezing, and cough more severe at night, in the early morning and generally worse following exercise particularly in cold air. At the onset of asthma cough may be the only symptom.

Acute exacerbation of chronic bronchitis results from various causes but infection is involved in about 50% of the cases, mostly viral and most often due to a rhinovirus. Viral infection can be associated to bacterial infection and the most frequently isolated germs are Streptococcus pneumoniae, Haemophilus influenzae, and B. catarrhalis. Severity assessment relies on the value of basal FEV1 that is often non available. Therefore Afssaps suggests using a dyspnea index to assess exacerbation severity[2].

Chronic airway inflammation in chronic severe asthma is characterized in most cases, both in central and peripheral airways, by the same pathological features of mild-moderate persistent asthma with an increased number of activated T lymphocytes, particularly CD4 Th2 cells, and sometimes eosinophils and mast cells. The most notable difference of chronic severe asthma compared with mild to moderate disease is the increased number of neutrophils. Chronic airway inflammation in stable chronic obstructive pulmonary disease is characterized, both in central and peripheral airways, by an increased number of T lymphocytes, particularly CD8+, macrophages and neutrophils. Macrophage and neutrophil counts increase with the progression of the severity of the disease [3].

References

1. Wilson R, Rayner CF. Bronchitis. Curr Opin Pulm Med. 1995 May;1(3):177-82.

Housset B. Definition of low respiratory tract infections. Med Mal Infect. 2006 Nov-Dec;36(11-12):538-45. Epub 2006 Jul 11.

3. Caramori G, Pandit A, Papi A. Is there a difference between chronic airway inflammation in chronic severe asthma and chronic obstructive pulmonary disease? Curr Opin Allergy Clin Immunol. 2005 Feb;5(1):77-83.