What is bronchitis?

Definition of Bronchitis

Bronchitis is an inflammatory condition of the tracheobronchial tree that can be acute or chronic, characterized primarily by cough with or without sputum production. 1

Acute Bronchitis

Acute bronchitis is defined as an acute respiratory infection manifested predominantly by cough with or without phlegm production that lasts for up to 3 weeks. 1

Key characteristics include:

• Duration: Symptoms typically last 1-3 weeks 2
• Absence of infiltrate on chest radiograph (which would suggest pneumonia) 1
• Often accompanied by constitutional symptoms such as fever, muscle aches, and fatigue 1

Etiology

• Primarily viral in origin (>90% of cases) 3
• Common viral causes include:
  • Adenovirus
  • Rhinovirus
  • Coronavirus
  • Influenza
  • Parainfluenza
  • Respiratory syncytial virus (RSV)
  • Coxsackievirus 1
• Less commonly caused by bacteria:
  • Mycoplasma pneumoniae
  • Chlamydia pneumoniae
  • Legionella species 1

Diagnosis

A diagnosis of acute bronchitis should only be made when:

1. Cough is the predominant symptom
2. Duration is less than 3 weeks
3. No clinical or radiographic evidence of pneumonia exists
4. Common cold, acute asthma, or COPD exacerbation have been ruled out 1

Chronic Bronchitis

Chronic bronchitis is defined as cough and excessive secretion of mucus in patients who have coughed up sputum on most days during 3 consecutive months for more than 2 successive years. 1, 4

Etiology

Primary causes include:

• Prolonged exposure to pulmonary irritants, with cigarette smoke being the most prominent 1
• Atmospheric pollution
• Recurrent episodes of infection 1

Clinical Implications

The chronic bronchitic phenotype carries important clinical implications:

• Accelerated lung function decline
• Higher risk of respiratory infections
• Increased frequency of exacerbations 4

Diagnosis

To diagnose chronic bronchitis:

1. Confirm chronic cough and sputum production for ≥3 months/year for 2 consecutive years
2. Rule out other respiratory or cardiac causes of chronic productive cough
3. Obtain a complete history regarding exposures to respiratory irritants 4

Distinguishing Features and Pitfalls

Common Diagnostic Challenges

• The clinical distinction between acute bronchitis and the common cold can be difficult or sometimes impossible to make 1
• Acute asthma is commonly misdiagnosed as acute bronchitis (in approximately one-third of patients presenting with acute cough) 1
• For patients who have had at least two similar doctor-diagnosed episodes of acute bronchitis in the past 5 years, 65% can be identified as having mild asthma 1

When to Consider Other Diagnoses

• When cough persists for more than 3 weeks, consider:
  • Postinfectious cough
  • Upper airway cough syndrome
  • Asthma
  • Gastroesophageal reflux disease 1

Management Considerations

Acute Bronchitis

• Acute bronchitis is self-limiting; treatment focuses on symptom relief 5
• Antibiotics are generally not indicated and should not be offered routinely 1, 3
• Patient education regarding the expected duration of cough (2-3 weeks) is important 5

Chronic Bronchitis

• Management involves addressing underlying causes (e.g., smoking cessation) 6
• For acute exacerbations of chronic bronchitis, antibiotic selection should consider:
  • Patient co-morbidities
  • Likely pathogens
  • Resistance issues
  • Individual antibiotic properties 6

By understanding the definitions, causes, and distinguishing features of bronchitis, clinicians can provide appropriate diagnosis and management while avoiding unnecessary treatments.