What are the causes of Chronic Obstructive Pulmonary Disease (COPD) exacerbations?

Causes of COPD Exacerbations

COPD exacerbations are primarily triggered by respiratory viral infections, bacterial infections, and environmental factors, with respiratory tract infections being the most common cause. 1

Main Causes of COPD Exacerbations

1. Infectious Causes

• Viral infections (responsible for approximately 48.4% of exacerbations) 2

  • Rhinovirus (common cold)
  • Coronavirus
  • Influenza B
  • Parainfluenza 1

• Bacterial infections (responsible for approximately 54.7% of exacerbations) 2

  • Streptococcus pneumoniae
  • Moraxella catarrhalis
  • Haemophilus influenzae 1
  • Note: Bacterial exacerbations often involve new strains of existing colonizing organisms 1

• Viral/bacterial coinfections (approximately 25% of cases) are associated with:

  • More severe lung function impairment
  • Longer hospitalizations
  • Worse outcomes 2

2. Environmental Factors

• Air pollution
• Respiratory irritants
• Cigarette smoke exposure 1

Inflammatory Patterns During Exacerbations

• Neutrophilic inflammation:

  • Present in all exacerbations
  • Directly related to exacerbation severity
  • Associated with increased airway inflammation, mucus production, and gas trapping 1, 2

• Eosinophilic inflammation:

  • Specifically increased during virus-associated exacerbations
  • May predict viral etiology 2

Clinical Presentation of Exacerbations

COPD exacerbations are characterized by:

• Increased dyspnea (key symptom)
• Increased sputum volume
• Increased sputum purulence
• Increased cough and wheeze 1

Classification of Exacerbations

1. Mild: Treated with short-acting bronchodilators only
2. Moderate: Treated with short-acting bronchodilators plus antibiotics and/or oral corticosteroids
3. Severe: Requiring hospitalization or emergency room visit; may be associated with acute respiratory failure 1

Important Clinical Considerations

• Exacerbations typically last 7-10 days, but 20% of patients have not recovered to their pre-exacerbation state even after 8 weeks 1

• Patients with frequent exacerbations (≥2 per year) have:

  • Worse health status
  • Higher morbidity
  • Faster disease progression 1

• Risk factors for more frequent/severe exacerbations include:

  • Increased pulmonary artery to aorta ratio >1
  • Greater percentage of emphysema on CT
  • Increased airway wall thickness
  • Worse lung function
  • Lower exercise capacity
  • Chronic bronchitis 1

Differential Diagnosis

Always rule out other conditions that can mimic COPD exacerbations:

• Acute coronary syndrome
• Worsening congestive heart failure
• Pulmonary embolism
• Pneumonia
• Pneumothorax 1

Clinical Pitfalls to Avoid

1. Missing coinfections: Patients with both viral and bacterial infections have worse outcomes and require more aggressive treatment 2

2. Overlooking comorbidities: When the character of cough changes for prolonged periods, consider complications like bronchogenic carcinoma 1

3. Underestimating exacerbation frequency: Many exacerbations are unreported by patients despite causing significant health deterioration 3

4. Delayed treatment: Early intervention, especially when a COPD patient develops a cold, may reduce exacerbation severity and duration 3

5. Inadequate follow-up: Physiologic recovery after exacerbations is often incomplete, which decreases quality of life and resistance to future exacerbations 3