Acute bronchitis is inflammation of the tracheobronchial tree, commonly following a URI, that occurs in patients without chronic lung disorders. The cause is almost always a viral infection. The pathogen is rarely identified. The most common symptom is cough, with or without fever, and possibly sputum production. Diagnosis is based on clinical findings. Treatment is supportive; antibiotics are usually unnecessary. Prognosis is excellent.
Acute bronchitis is frequently a component of a URI caused by rhinovirus, parainfluenza, influenza A or B virus, respiratory syncytial virus, coronavirus, or human metapneumovirus. Less common causes may be Mycoplasma pneumoniae, Bordetella pertussis, and Chlamydia pneumoniae. Less than 5% of cases are caused by bacteria, sometimes in outbreaks.
Acute inflammation of the tracheobronchial tree in patients with underlying chronic bronchial disorders (eg, COPD, bronchiectasis, cystic fibrosis) is considered an acute exacerbation of that disorder rather than acute bronchitis. In these patients, the etiology, treatment, and outcome differ from those of acute bronchitis (see also Treatment of Acute COPD Exacerbation).
Symptoms are a nonproductive or mildly productive cough accompanied or preceded by URI symptoms, usually by > 5 days. Subjective dyspnea results from chest pain or tightness with breathing, not from hypoxia. Signs are often absent but may include scattered rhonchi and wheezing. Sputum may be clear, purulent, or occasionally contain blood. Sputum characteristics do not correspond with a particular etiology (ie, viral vs bacterial). Mild fever may be present, but high or prolonged fever is unusual and suggests influenza or pneumonia.
On resolution, cough is the last symptom to subside and often takes 2 to 3 wk or even longer to do so.
Diagnosis is based on clinical presentation. Testing is usually unnecessary. However, patients who complain of dyspnea should have pulse oximetry to rule out hypoxemia. Chest x-ray is done if findings suggest serious illness or pneumonia (eg, ill appearance, mental status change, high fever, tachypnea, hypoxemia, crackles, signs of consolidation or pleural effusion). Elderly patients are the occasional exception, as they may have pneumonia without fever and auscultatory findings, presenting instead with altered mental status and tachypnea.
Sputum Gram stain and culture usually have no role. Nasopharyngeal samples can be tested for influenza and pertussis if these disorders are clinically suspected (eg, for pertussis, persistent and paroxysmal cough after 10 to 14 days of illness, only sometimes with the characteristic whoop and/or retching, exposure to a confirmed case—see also Pertussis : Diagnosis).
Cough resolves within 2 wk in 75% of patients. Patients with persistent cough should undergo a chest x-ray. Evaluation for noninfectious causes, including postnasal drip and gastroesophageal reflux disease, can usually be done clinically. Differentiation of cough-variant asthma may require pulmonary function testing.
Acute bronchitis in otherwise healthy patients is a major reason that antibiotics are overused. Nearly all patients require only symptomatic treatment, such as acetaminophen and hydration. Evidence supporting efficacy of routine use of other symptomatic treatments, such as antitussives, mucolytics, and bronchodilators, is weak. Antitussives should be considered only if the cough is interfering with sleep (see Treatment). Patients with wheezing may benefit from an inhaled β2-agonist (eg, albuterol) or an anticholinergic (eg, ipratropium) for a few days. Oral antibiotics are typically not used except in patients with pertussis or during known outbreaks of bacterial infection. A macrolide such as azithromycin 500 mg po once, then 250 mg po once/day for 4 days or clarithromycin 500 mg po bid for 14 days is given.