Acute Bronchitis

Overview

Definition

Acute bronchitis is an acute inflammation of the large airways of the lower respiratory tract wherein the pulmonary parenchyma is not affected.

• Occurs due to a viral or bacterial infection
• Often preceded by an upper respiratory tract infection (URTI) due to similar etiologies
• Viral acute bronchitis can develop into a secondary bacterial superinfection.

Epidemiology

Acute bronchitis is a very common disease.

• Incidence: 
  • Approximately 5% of adults have an episode of acute bronchitis every year.
  • Among the top 10 conditions for which patients seek medical attention
• Occurrence: more frequent during late fall and the winter months
• Gender preference: affects both genders equally
• Age preference: children and adolescents affected more commonly than adults

Etiology

Acute bronchitis is most commonly caused by a viral infection, although bacterial causes are possible.

• Viral bronchitis: responsible for approximately 95% of all cases of acute bronchitis
  • Influenza A and B
  • Parainfluenza
  • Respiratory syncytial virus (RSV)
  • Rhinoviruses
  • Coronaviruses
    • Includes Types 1, 2, and 3
    • SARS-coronavirus-2 (SARS-CoV-2)
• Bacterial acute bronchitis: only responsible for approximately 5% of cases
  • Mycoplasma pneumoniae
  • Chlamydia pneumoniae
  • Bordetella pertussis
  • Rare causative agents, typically occurring only with airway instrumentation or chronic obstructive pulmonary disease (COPD):
    • Streptococcus pneumoniae
    • Staphylococcus aureus
    • Haemophilus influenzae
    • Moraxella catarrhalis
• Risk factors:
  • Chronic lung disease (e.g., COPD, asthma)
  • Smoking
  • Chronic exposure to air pollution

Pathophysiology

Acute bronchitis is characterized by infection and inflammation of the cells of the tissue lining the bronchi.

• Irritation and inflammation cause:
  • Impaired ciliary function
  • Hyperemia and edema in the mucous membrane
  • Decreased bronchial mucociliary function
  • Increased mucus production → characteristic cough of acute bronchitis
• Bronchopneumonia may develop if the inflammation extends downward to the bronchioles and lung parenchyma.

Clinical Presentation

Acute bronchitis is typically a self-limiting condition with a prominent cough lasting 1–3 weeks.

• Cough (the predominant symptom):
  • Acute onset
  • Productive with clear, yellow, or purulent sputum
  • Note: Purulent sputum is not specific to bacterial causes.
• Chest soreness from frequent coughing
• Wheezing
• Rhonchi that clear with coughing
• Mild dyspnea
• Malaise
• Fever:
  • Possible, but uncommon in acute bronchitis
  • Usually low grade if present
  • Should raise concern for possible pneumonia or bacterial superinfection
• An URTI (“common cold”) often precedes acute bronchitis and may present with symptoms overlapping the onset of acute bronchitis:
  • Headache
  • Nasal congestion
  • Sore throat
• Findings that are more consistent with pneumonia than acute bronchitis:
  • Fever
  • Tachypnea
  • Rales
  • Dullness to percussion
  • Egophony
  • Tactile fremitus

Diagnosis

Acute bronchitis is typically a clinical diagnosis that relies on history and exam, and should be suspected in patients with an acute onset of cough, which often follows a URTI without findings of pneumonia. Additional work-up may include:

Chest X-ray

• To rule out pneumonia
• Indications:
  • Signs of consolidation on exam:
    • Dullness to percussion
    • Egophony
    • Tactile fremitus
  • Abnormal vital signs: 
    • Fever
    • Tachycardia
    • Tachypnea
    • ↓ Oxygen saturation
  • Mental status or behavioral changes in the elderly (> 75 years of age)
  • Immunocompromised patients
• Findings:
  • Usually normal in acute bronchitis
  • May show thickening of the bronchial walls in the lower lobes
  • Infiltrates/consolidation indicate pneumonia.

Microbiological testing

• Rarely indicated because results rarely change management
• Not recommended except during suspected outbreaks: Gram stain and sputum culture (because bacterial causes are rare)
• Consider testing for influenza: 
  • Fever and cough during influenza season
  • Children < 2 years of age
  • Adults > 65 years of age
  • Pregnant women
  • Nursing-home residents
  • Immunocompromised patients
  • Medical comorbidities:
    • Asthma
    • COPD
    • Cystic fibrosis
    • Heart, kidney, liver, endocrine, or blood disorders
    • BMI ≥ 40
• Consider testing for pertussis:
  • Paroxysmal cough with inspiratory whoop
  • Post-tussive emesis
• Consider testing for COVID-19: all individuals with respiratory infections during the pandemic

Management

Acute bronchitis is typically a self-limiting condition that usually requires only supportive care.

Patient education

• Symptoms resolve spontaneously within 1‒3 weeks.
• Explain why antibiotics are not indicated to patients who request them.
• Discuss better treatments for symptom reduction.

Treatments for symptom reduction

• For cough: 
  • Nonpharmacological therapy (no data on efficacy, but low risk and may help):
    • Hot tea
    • Throat lozenges
    • Honey
  • Antitussive agents (efficacy is uncertain, but clinical-practice guidelines recommend offering them to decrease antibiotic use):
    • Dextromethorphan (Robitussin)
    • Guaifenesin (Mucinex)
    • Codeine (generally avoided due to addictive potential)
• For malaise, myalgias, and fever: 
  • Analgesic antipyretics:
    • NSAIDs
    • Acetaminophen
• For wheezing: beta-agonists (Albuterol)
• For patients with underlying lung disease (COPD, asthma):
  • Prednisone
  • Optimize therapy for underlying conditions.
  • Consider antimicrobials in cases of known or suspected bacterial infections.

Antimicrobials

Antibiotics are specifically NOT recommended in acute bronchitis in otherwise healthy adults. There is strong evidence to support avoiding antibiotics, although inappropriate overprescribing is still common.

• Risks of antibiotic therapy:
  • Alterations of the microbiome, which may impair immune function
  • Clostridium difficile infection
  • Increased antibiotic resistance
• Indications for antimicrobials in the case of an identified treatable pathogen:
  • Influenza: neuraminidase inhibitors (e.g., oseltamivir, zanamivir)
  • Pertussis: macrolides (e.g., azithromycin, erythromycin)
  • COVID-19: complex management with changing guidelines
• Other bacterial causes of acute bronchitis:
  • Antibiotics are generally not recommended in the absence of pneumonia.
  • Consider therapy in patients with underlying lung conditions and/or in individuals at high risk for complications.

Lifestyle modifications

• Smoking cessation
• Avoidance of allergens/pollutants
• Flu and pneumonia vaccines according to standard guidelines

Differential Diagnosis

• Pneumonia: an infection of the lung parenchyma most commonly caused by bacteria or viruses. Community-acquired pneumonia (CAP) accounts for 80% of the cases. Diagnosis of pneumonia is based on the clinical presentation of fever, productive cough, dyspnea, rales, and consolidation on chest X-ray. Empirical antibiotic treatment is generally appropriate for CAP, whereas pneumonia in a ventilated patient often requires culture-based therapy.
• Influenza: a highly contagious and febrile respiratory disease. Influenza typically presents with a fever, myalgia, headache, and symptoms of a URTI. Symptoms of gastroenteritis may also occur more commonly in children. The diagnosis is usually clinical, although testing options are available. A chest X-ray is warranted in patients at high risk for pneumonia or for individuals exhibiting symptoms of a complicating viral or secondary bacterial pneumonia. Management may include neuraminidase and M2 inhibitors when started early.
• Pertussis: a potentially life-threatening bacterial infection, also known as whooping cough, which presents with an intense paroxysmal cough followed by an inspiratory “whooping” sound and/or post-tussive vomiting. Pertussis can be severe in infants < 1 year of age. If pertussis is suspected, immediate antibiotic therapy with macrolides should be initiated even if laboratory confirmation is pending. Pertussis is preventable with immunization.
• Bronchiolitis: a respiratory condition caused by inflammation of the bronchioles with the majority of cases caused by RSV, which affects children. Patients usually present with upper respiratory symptoms initially, such as cough and congestion, which may progress to dyspnea, wheezing, and hypoxia. Diagnosis is clinical and treatment is directed at improving oxygenation and hydration. Bronchiolitis is a self-limiting condition with a good prognosis.
• Acute sinusitis: a viral (most common), bacterial, or fungal upper respiratory infection that results in inflammation of the mucosal lining of the paranasal sinuses. Acute sinusitis usually occurs concurrently with inflammation of the nasal mucosa and presents with facial pain over the affected sinus and purulent rhinorrhea. Diagnosis is usually clinical, and management is supportive. Antibiotics are indicated in the less common cases of bacterial sinusitis.
• Asthma: a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. Asthma typically presents with wheezing, cough, and dyspnea. Diagnosis is confirmed with a pulmonary function test showing a reversible obstructive pattern. Treatment is with bronchodilators and inhaled corticosteroids.
• Foreign-body aspiration: Aspirated foreign bodies may lodge in the bronchi, affect breathing, and lead to infection or erosion of the bronchial walls. Foreign bodies are more frequently aspirated by children who may present with coughing or wheezing. Diagnosis is made based on imaging studies, and treatment is aimed at promptly removing the foreign body.
• GERD: occurs when the stomach acid frequently flows back into the esophagus. Acid reflux can irritate the lining of the esophagus and cause symptoms such as retrosternal burning pain, regurgitation, cough, and a sore throat. Diagnosis is usually clinical, but ambulatory pH monitoring may confirm the diagnosis. Management is based on lifestyle modifications and treatment with acid-reducing drugs.
• Heart failure: refers to the inability of the heart to supply the body with enough output to meet its metabolic needs. Presentation of heart failure includes chest pain, dyspnea on exertion, cough that worsens on reclining, fatigue, pitting edema, and crackles on exam. An echocardiogram and cardiac stress test will show reduced cardiac function. A chest X-ray will show pulmonary edema. Management is with multiple pharmacological agents and lifestyle modifications.