Acute bronchitis is a very common disease with symptoms relating to temporary inflammation of the airways of the lungs. It is caused by virus infections in over 95% of cases. A small minority of cases is caused by bacteria; however there is little evidence that antibiotics are effective in the treatment of the condition.
Acute bronchitis, one of the most common diagnoses in ambulatory care medicine, accounted for approximately two and a half million visits to physicians in 2017. This condition consistently ranks as one of the top ten diagnoses for which patients seek medical care, with cough being the most frequently mentioned symptom necessitating office evaluation. In the European countries, treatment costs for acute bronchitis are enormous: for each episode, patients receive an average of two prescriptions and miss two to three days of work. Even though acute bronchitis is a common diagnosis, its definition is unclear.
The diagnosis is based on clinical findings, without standardized diagnostic signs and sensitive or specific confirmatory laboratory tests. Consequently, physicians exhibit extensive variability in diagnostic requirements and treatment. Antibiotic therapy is used in 65 to 80 percent of patients with acute bronchitis but a growing base of evidence puts this practice into question. This article examines the diagnosis and treatment of acute bronchitis in otherwise healthy, nonsmoking patients, with a focus on symptomatic therapy and the role of antibiotics in treatment. Patho-physiology and Etiology Acute bronchitis was originally described in the 19th century as inflammation of the bronchial mucous membranes.
Over the years, this inflammation has been shown to be the result of a sometimes complex and varied chain of events. An infectious or noninfectious trigger leads to bronchial epithelial injury, which causes an inflammatory response with airway hyper-responsiveness and mucus production. Acute bronchitis is usually caused by a viral infection. In patients younger than one year, respiratory syncytial virus, para-influenza virus, and coronavirus are the most common isolates. In patients one to 10 years of age, parainfluenza virus, enterovirus, respiratory syncytial virus, and rhinovirus predominate. In patients older than ten years, influenza virus, respiratory syncytial virus, and adenovirus are most frequent.
Factors Affecting Chronic Bronchitis
A chronic or recurrent insult to the airway epithelium, such as recurrent aspiration or repeated viral infection may contribute to chronic bronchitis in childhood. Thus, it may be caused by repeated attacks of acute bronchitis, which can weaken and irritate bronchial airways with time. Following damage to the airway lining, chronic infection by commonly isolated airway organisms may occur. Industrial pollution is a common cause; however, the chief reason is heavy long term exposure to cigarette smoke. In children, chronic bronchitis follows either an endogenous response (eg. excessive inflammation) to acute air flow injury or continuous exposure to certain obnoxious environmental agents (eg. allergens or irritants).
Signs and Symptoms
The major symptom of acute bronchitis is cough. The cough may be associated with mucus production, which may be clear to yellow or green in colour. Some people may have an audible noise on breathing which can be a whistle/wheeze or a rattle. There may be other symptoms associated with the viral cause such as a runny nose, sore throat, muscle aches and pains, sore eyes or headache, particularly early in the illness. Chest pain is not a symptom usually associated with bronchitis.
Classifying an upper respiratory infection as bronchitis is imprecise. However, studies of bronchitis and upper respiratory infections often use the same constellation of symptoms as diagnostic criteria. Cough is the most commonly observed symptom of acute bronchitis. The cough begins within two days of infection in 85 percent of patients. Most patients have a cough for less than two weeks; however, 26 percent are still coughing after two weeks, and a few cough for six to eight weeks. When a patient’s cough fits this general pattern, acute bronchitis should be strongly suspected.
Although most physicians consider cough to be necessary to the diagnosis of acute bronchitis, they vary in additional requirements. Other signs and symptoms may include sputum production, dyspnea, wheezing, chest pain, fever, hoarseness, malaise, rhonchi, and rales. Each of these may be present in varying degrees or may be absent altogether. Sputum may be clear, white, yellow, green, or even tinged with blood. Peroxidase released by the leukocytes in sputum causes the color changes; hence, color alone should not be considered indicative of bacterial infection.
Physical Examination and Diagnostic Studies
The physical examination of patients presenting with symptoms of acute bronchitis should focus on vital signs, including the presence or absence of fever and tachypnea, and pulmonary signs such as wheezing, rhonchi, and prolonged expiration. Evidence of consolidation must be absent. Fever may be present in some patients with acute bronchitis. However, prolonged or high-grade fever should prompt consideration of pneumonia or influenza. Recommendations on the use of Gram staining and culture of sputum to direct therapy for acute bronchitis vary, because these tests often show no growth or only normal respiratory flora.
In one recent study, nasopharyngeal washings, viral serologies, and sputum cultures were obtained in an attempt to find pathologic organisms to help guide treatment. In more than two thirds of these patients, a pathogen was not identified. Similar results have been obtained in other studies. Hence, the usefulness of these tests in the outpatient treatment of acute bronchitis is questionable. Despite improvements in testing and technology, no routinely performed studies diagnose acute bronchitis. Chest radiography should be reserved for use in patients whose physical examination suggests pneumonia or heart failure, and in patients who would be at high risk if the diagnosis were delayed.
Included in the latter group are patients with advanced age, chronic obstructive pulmonary disease, recently documented pneumonia, malignancy, tuberculosis, and immuno-compromised or debilitated status. Office spirometry and pulmonary function testing are not routinely used in the diagnosis of acute bronchitis. These tests are usually performed only when underlying obstructive pathology is suspected or when patients have repeated episodes of bronchitis.
Since acute bronchitis is most often caused by a viral infection, usually only symptomatic treatment is required. Treatment can focus on preventing or controlling the cough or on making the cough more effective. Protrusive therapy is indicated when coughing should be encouraged (e.g., to clear the airways of mucus). In randomized, double-blind, placebo-controlled studies of protrusive in patients with cough from various causes, only terbutaline, amiloride, and hypertonic saline aerosols proved successful.
However, the clinical utility of these agents in patients with acute bronchitis is questionable, because the studies examined cough resulting from other illnesses. Anti-intrusive therapy is indicated if cough is creating significant discomfort and if suppressing the body’s protective mechanism for airway clearance would not delay healing. Studies have reported success rates ranging from 68 to 98 percent.18Antitussive selection are based on the cause of the cough. For example, an antihistamine would be used to treat cough associated with allergic rhinitis, a decongestant or an antihistamine would be selected for cough associated with postnasal drainage, and a bronchodilator would be appropriate for cough associated with asthma exacerbations.