Description

• Infection (usually viral) of respiratory bronchial tree with transient inflammatory changes, bronchial edema, and mucus formation leading to symptoms of airway obstruction

Incidence

• 2.5 million patients diagnosed with acute bronchitis annually in the United States.
• Standardized incidence: 4.7 cases per 100 patients per year

ICD-9 codes

• 466.0 acute bronchitis
• 490 bronchitis, not specified as acute or chronic
• 491.22 obstructive chronic bronchitis with acute bronchitis
• 506.0 bronchitis and pneumonitis due to fumes and vapors

Causes

• Viruses are the most common cause of acute bronchitis in otherwise healthy adults.
— Common viral causes in fall, winter, and spring include rhinovirus, respiratory syncytial virus (RSV), parainfluenza, influenza A and B, coronavirus, and adenovirus.
— Common viral causes in summer months include rhinoviruses, coxsackieviruses, and echoviruses.
• A minority of infections caused by nonviral agents
— Mycoplasma pneumoniae or Chlamydia pneumoniae are most common nonviral infectious causes.
— Other causes include legionella, Hemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, and Bordetella pertussis.
• Acute bronchitis may have causes other than infection.
— Asthma with mucosal injury due to acute event, such as smoke or chemical inhalation
— Chronic toxic exposure, such as cigarette smoking
— Inhalation of toxic substances: sulfur dioxide, nitrogen dioxide, ammonia

Pathogenesis

• Irritants result in bronchial edema and mucus formation.
• Inflammation and mucus leads to sputum production, cough, and symptoms of airway obstruction.
• Patients with acute bronchitis may have underlying predisposition to bronchial reactivity during viral infection.
• Immune suppression may increase risk of infectious disease.

Presentation

• Symptoms generally last 7-10 days.
• Common symptoms:
— Cough 
 Night cough or wheezing may be only signs of bronchial obstruction.
 Fatigue from night cough often prompts office visit.
— Wheezing
— Sometimes dyspnea on exertion
• Patients often have accompanying cold symptoms (sore throat, nasal symptoms).
• Sputum may be clear or purulent; appearance and color are not predictive of bacterial infection.

Differential diagnosis

• Congestive heart failure: Consider if paroxysmal nocturnal dyspnea, orthopnea, rales (crackles), edema, or jugular venous distension.
• Pneumonia: Consider if tachycardia, tachypnea, fever, or abnormal chest x-ray.
• Pertussis: Consider if cough persists longer than two to three weeks.
• TB: Consider if persistent cough, weight loss, night sweats.
• Other reactive airway disease: asthma, allergic aspergillosis, occupational exposures, chronic bronchitis
• Other respiratory infection: sinusitis, common cold, pharyngitis, Pneumocystis carinii (in immunocompromised)
• Other causes of cough or wheeze: ACE inhibitor use, reflux esophagitis (with chronic aspiration), bronchogenic tumor, other aspiration syndromes, smoke inhalation or other toxic inhalational exposure, bronchiectasis, foreign-body aspiration

Possible physical findings

• Low-grade fever
• Rhinitis
• Pharyngitis
• Lymphadenopathy
• Lung examination useful but not diagnostic
• Forced expiration can detect wheezing.
• Prolonged expiratory phase or other signs of obstruction, but patient may have no signs of bronchospasm.

Evaluation

• No clear diagnostic criteria have been established.
• The evaluation of adults with an acute cough or presumptive diagnosis of uncomplicated acute bronchitis should focus on clinically ruling out pneumonia.
• Chest x-ray is generally not indicated in a healthy non-
elderly adult without vital-sign abnormalities or asymmetric lung sounds.
• Chest x-ray is warranted for patients with cough lasting more than three weeks in the absence of other known causes.
• Peak flow spirometry may help detect obstructive airway conditions. Pulmonary function testing is unnecessary in otherwise healthy patients.
• Pulse oximetry may be helpful if pneumonia is suspected.
• Sputum culture is generally not helpful — usually negative or shows “normal respiratory flora.”

Treatment

• Antibiotics not generally recommended
— CDC evidence-based guidelines conclude that routine antibiotic treatment of uncomplicated acute bronchitis is not recommended, regardless of duration of cough.
— Antibiotics provide very limited benefit.
 May reduce incidence of cough at 7-11 days (five patients need to be treated with antibiotics for one to achieve this benefit, compared with placebo)
 May shorten duration of cough by 0.5-0.6 days
 Associated with adverse effects, such as nausea, vomiting, headache, rash, or vaginitis (one additional adverse effect for every 17 patients treated, compared with placebo)
 No antibiotic has been proven significantly more effective than amoxicillin.
• Symptom relief
— Relief of symptoms will not shorten duration of illness, but patients may benefit from analgesics, antipyretics, ß-agonist inhalers, antitussives, or vaporizers.
— Bronchodilators (e.g., albuterol metered-dose inhaler two puffs every four hours p.r.n.) may be helpful in patients with evidence of airflow obstruction, but supporting evidence is limited.
— There is no good evidence for or against use of oral OTC medicines for acute cough, except:
 Limited evidence suggests guaifenesin may be helpful in adults.
 Codeine is no more effective than placebo in reducing cough but causes drowsiness and may improve sleep (avoid before driving or operating heavy machinery).
 Antihistamines and dextromethorphan are ineffective in children and cause side effects.
— An herbal remedy (Pelargonium sidoides extract [EPs 7630] 30 drops t.i.d. for seven days) reduced symptoms and improved ability to return to work by almost two days in a single randomized placebo-controlled trial of 468 adults treated within 48 hours of onset.
• Smoking cessation is important to restore ciliary action and prevent recurrence or chronic bronchitis.
• Increasing fluid intake during respiratory infection has unknown effects: no evidence was found in a systematic review.

Prognosis

• Inflammation is generally transient and resolves soon after the infection is cleared, so most symptoms resolve in 7-10 days.
• But cough and irritation can last significantly longer.
— Cough lasts up to three weeks in 50% of patients.
— Cough lasts longer than one month in 25% of patients.
— Rarely, post-bronchitis cough can last for six months.
• For patients with prolonged cough or worsening symptoms:
— Consider chronic obstructive airway disease (asthma or chronic bronchitis) and noninfectious causes.
— Cough with viral bronchitis may persist for months, and there is no good evidence to guide treatment of prolonged infectious cough.
— Prolonged cough may occasionally be associated with pertussis, M. pneumoniae, C. pneumoniae, or TB.
— In patients exposed to B. pertussis, antibiotics may not provide direct benefit but may help prevent spread. n

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