What causes Acute Exacerbation of Chronic Obstructive Pulmonary Disease (AECOPD)?

Causes of Acute Exacerbation of Chronic Obstructive Pulmonary Disease (AECOPD)

Acute exacerbations of COPD are primarily caused by respiratory infections (viral and bacterial), air pollution, and in some cases, by exacerbations of concomitant chronic diseases such as cardiovascular conditions. 1, 2

Primary Infectious Causes

• Viral infections account for approximately one-third of AECOPD episodes, with common culprits including rhinovirus, coronavirus, influenza B, and parainfluenza 3
• Bacterial infections are frequently implicated, with common pathogens including Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae 3
• Molecular typing of sputum isolates has shown that acute exacerbations are often associated with a new strain of a preexisting bacterial organism, supporting the causative role of bacteria 3
• Viral respiratory infections can predispose airways to bacterial superinfection by interfering with mucociliary clearance, impairing bacterial killing by pulmonary macrophages, and increasing the risk of aspirating secretions containing bacteria 3

Environmental Triggers

• Air pollution can trigger or contribute to the onset of an exacerbation 2
• Environmental stressors can precipitate sudden worsening in airway function and respiratory symptoms 1

Comorbidity-Related Causes

• Cardiovascular conditions can trigger or mimic AECOPD, including:
  • Systemic arterial hypertension 3
  • Acute heart decompensation/heart failure 3, 4
  • Atrial fibrillation 3
  • Pulmonary embolism 3, 5
• Other conditions that may trigger or complicate AECOPD:
  • Pneumonia 5
  • Pneumothorax 5, 1
  • Lung cancer 5

Pathophysiological Mechanisms

• Exacerbations are characterized by:
  • Increased airway and systemic inflammation 2
  • Greater production of mucus 6
  • Airway hyperinflation 2
  • Increased cough and wheeze 5
  • Increased sputum purulence and volume 5

Clinical Presentation and Classification

• The key symptom of an exacerbation is increased dyspnea, often accompanied by:

  • Increased sputum purulence and volume 5
  • Increased cough 5
  • Wheeze 5

• Exacerbations are classified as:

  • Type 1: Increased dyspnea, sputum volume, and sputum purulence 7
  • Type 2: Any two of the above symptoms 7
  • Type 3: One of the above symptoms plus cough, wheeze, or symptoms of upper respiratory tract infection 7

Important Clinical Considerations

• Some patients are particularly susceptible to frequent exacerbations (defined as two or more per year), showing worse health status and faster disease progression 6, 2
• Exacerbations may adversely affect the natural history of COPD 8
• Many exacerbations are unreported by patients despite considerable symptom changes 7
• When a COPD patient develops a cold, they should be considered for early therapy as colds are associated with longer and more severe exacerbations 7
• Physiologic recovery after an exacerbation is often incomplete, which decreases health-related quality of life and resistance to future exacerbations 7

Diagnostic Approach

• Chest radiography is essential to exclude pneumonia, pneumothorax, pulmonary edema, and lung cancer 5
• Differential diagnoses that must be excluded include acute coronary syndrome, worsening congestive heart failure, and pulmonary embolism 5
• Sputum culture and sensitivity are recommended when purulent sputum is present, previous antibiotic treatment was ineffective, or in severe exacerbations requiring hospitalization 5

Remember that AECOPD is a clinical diagnosis based on acute worsening of respiratory symptoms that requires additional therapy, and other causes of respiratory deterioration should be excluded before confirming the diagnosis 5, 1.