Bronchitis overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Bronchitis Main page |
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), for at least three months in two consecutive years. The remainder of this article deals with acute bronchitis only. This is caused by a viral infection, such as a cold, or a bacterial infection. It also can result from breathing irritating fumes, such as those of tobacco smoke or polluted air. Constant coughing is the main symptom. Either type(chronic or acute) may lead to asthma or pneumonia.
Acute bronchitis is characterized by cough and sputum (phlegm) production and symptoms related to the obstruction of the airways by the inflamed airways and the phlegm, such as shortness of breath and wheezing. Diagnosis is by clinical examination and sometimes microbiological examination of the phlegm. Treatment may be with antibiotics (if a bacterial infection is suspected), bronchodilators (to relieve breathlessness) and other treatments.
Historical Perspective
In 1985, University of Newcastle, Australia Professor Robert Clancy developed an oral vaccine for acute bronchitis. This vaccine was commercialised four years later as Broncostat.[2]
Pathophysiology
Acute bronchitis is the inflammatory response of the bronchial epithelium to infections or irritants. The pathophysiological finding seen with acute bronchitis include: thickening, hyperemia and edema of the bronchial mucosa. This in turn decreases the bronchial mucociliary function. As a result of which the air passages become clogged by debris and causes copious mucus secretion, which causes the characteristic cough of bronchitis.
Causes
Acute bronchitis is a self-limited inflammation of the large airways of the lung that is characterized by cough with or without sputum that last several days or weeks (10 days). It is one of the commonest causes of outpatient admission worldwide. Virus are thought to be the commonest cause of acute bronchitis.Influenza A and B, parainfluenza, respiratory synctial virus, corona virus are the commonest involved pathogens. Some atypical bacterias likemycoplasma, chlamydiae and bordetella pertusis are also found to cause acute bronchitis.
Differentiating Bronchitis from other Diseases
Acute bronchitis (inflammation of large airways) should be differentiated from asthma or bronchiolitis (acute inflammation of the small airways). Asthma and Bronchiolitis generally presents with cough accompanied by wheezing, tachypnea, respiratory distress, and hypoxemia. Whereas, bronchitis usually presents with cough last usually for 10 days with or without sputum. It should also be distinguished from bronchiectasis that is associated with chronic cough (due to permanent dilatation of bronchi). Additionally, chronic bronchitis should be ruled out. The diagnosis of chronic bronchitis is made in patients who have cough and sputum production on most days of the month for at least 3 months of the year during 2 consecutive years.Other diagnosis to keep in mind as differentials are: COPD, influenza, pharyngitis and sinusitis
Risk Factors
The people with increased risk for developing acute bronchitis includes elderly, infants and patients with underlying heart or lung diseases. Chronic bronchitis are commonly found in smokers.
Natural History, Complications and Prognosis
Acute Bronchitis usually presents with cough with or without sputum. The symptoms generally gets well within 10 days but may last for 4 weeks or more. Patients with recurrent episodes of acute bronchitis should be tested to rule out asthma.
Diagnosis
History and Symptoms
Bronchitis is usually a diagnosis of exclusion. Presence of cough without fever lasting more than 5 days and with normal vitals (no tachypnea or tachycardia) is suggestive of acute bronchitis. The presentation may vary according to the pathogen involved.
Physical Examination
A physical examination will often reveal decreased intensity of breath sounds, wheeze (rhonchi) and prolonged expiration. Most doctors rely on the presence of a persistent dry or wet cough as evidence of bronchitis.
Laboratory Findings
Acute bronchitis is usually a diagnosis of exclusion. A careful history and physical examination are very useful in doing a correct diagnosis. Other laboratory testings like antigen testing via multiplex PCR (polymerase chain reaction) and serological markers, can act as useful adjunct to the diagnosis. Nevertheless, these tests should be limited only for conditions when a pathogen is highly suspected, epidemic with a pathogen is present (influenza). These tests have limited availability and have not shown to be cost effective in outpatients department.
Treatment
Medical Therapy
Bronchitis is usually caused by a viral agent. The treatment of bronchitis is usually symptomatic with analgesics, decongestants, cough suppressant (codeine or hydrocodone-containing preparations or inhaled corticosteroids). Use of antibiotics should be limited to conditions when a diagnosis with a definitive pathogen is there. Oseltamivir for influenza (during influenza epidemics), and azithromycin for atypical bacterias like mycoplasma,chlamydiae has been shown useful in clinical trials.
References