Chronic Obstructive Pulmonary Disease

Definitions

  • COPD: A chronic, progressive lung disease characterised by airflow limitation that is not fully reversible. It is often associated with an abnormal inflammatory response to noxious particles or gases, most commonly from cigarette smoke.
  • Chronic bronchitis: Defined clinically as the presence of chronic productive cough for at least three months in two consecutive years. It is associated with inflammation and hypersecretion of mucus in the airways, leading to airway obstruction.
  • Emphysema: Refers to the destruction of the alveolar walls, leading to enlarged air spaces and reduced surface area for gas exchange. This results in loss of lung elasticity and airflow obstruction.Subtypes of Emphysema:
    1. Centrilobular (Centriacinar): Most commonly associated with smoking, primarily affects the respiratory bronchioles.
    2. Panlobular (Panacinar): More commonly associated with alpha1-antitrypsin deficiency, it affects the entire acinus, including the alveoli.

Causes and Pathophysiology of COPD

  • Smoking: The most significant risk factor.
  • Environmental exposures: Pollution, occupational dusts, and fumes.
  • Genetic factors: Alpha1-antitrypsin deficiency is a key genetic cause.
  • Ageing: Lung function naturally declines with age.

Pathophysiology: Chronic exposure to irritants (e.g., cigarette smoke) triggers inflammation, leading to airway narrowing and destruction of lung tissue (emphysema). Chronic bronchitis results in excessive mucus production, further narrowing the airways. Over time, these processes lead to airflow obstruction, hyperinflation, impaired gas exchange, and ultimately respiratory failure.

  • Alpha1-antitrypsin deficiency: A genetic disorder that leads to a lack of the protective protein alpha1-antitrypsin, which normally protects the lungs from neutrophil elastase. Without it, elastin in the lungs is broken down, leading to early-onset emphysema, even in non-smokers.

Signs and Symptoms of COPD

  • Chronic cough, often productive of sputum.
  • Dyspnoea (shortness of breath), especially on exertion.
  • Wheezing and chest tightness.
  • Frequent respiratory infections.
  • Fatigue, weight loss in advanced stages.

Diagnosis of COPD

  • Spirometry: A key diagnostic tool. It shows an FEV1/FVC ratio of <0.7 post-bronchodilator, confirming airflow limitation.
  • Chest X-ray: May show hyperinflation, flattened diaphragm, or evidence of emphysema.
  • CT scan: Provides detailed information about emphysema or other lung pathologies.
  • ABG (Arterial blood gas): Useful in advanced COPD or acute exacerbations to assess oxygenation and CO2 retention.
  • Alpha1-antitrypsin levels: Should be checked in younger patients or those with a family history of COPD.

GOLD Classification

COPD can be classified according to the GOLD criteria, which is based on the severity of airflow limitation (FEV1) and the patient’s symptoms:

  • GOLD Grades (based on post-bronchodilator FEV1):
    • Grade 1 (Mild): FEV1 ≥ 80% predicted.
    • Grade 2 (Moderate): 50% ≤ FEV1 < 80%.
    • Grade 3 (Severe): 30% ≤ FEV1 < 50%.
    • Grade 4 (Very severe): FEV1 < 30%.
  • GOLD Groups (based on symptoms and exacerbation risk):
    • Group A: Low symptoms, low risk of exacerbations.
    • Group B: High symptoms, low risk of exacerbations.
    • Group E: High risk of exacerbations, regardless of symptom burden.

Management of COPD

  • Lifestyle/supportive measures:
    • Smoking cessation: The most important intervention.
    • Vaccinations: Influenza and pneumococcal vaccines reduce exacerbations.
    • Pulmonary rehabilitation: Exercise and education to improve quality of life.
  • Medical management (GOLD criteria):
    • SABA/SAMA: Short-acting bronchodilators (e.g., salbutamol, ipratropium) for relief.
    • LABA/LAMA: Long-acting bronchodilators (e.g., tiotropium, salmeterol) for maintenance.
    • Inhaled corticosteroids: In combination with LABA/LAMA for patients with frequent exacerbations.
    • PDE-4 inhibitors: For severe COPD with chronic bronchitis.
  • Surgical options:
    • Lung volume reduction surgery: In selected patients with predominant emphysema.
    • Lung transplant: In end-stage COPD.
  • Palliative care: Focuses on symptom relief, including dyspnoea and anxiety management, particularly in advanced stages.

Long-term Oxygen Therapy (LTOT) Criteria

  • PaO2 ≤ 7.3 kPa or PaO2 between 7.3-8.0 kPa with evidence of peripheral oedema, polycythaemia, or pulmonary hypertension, measured on two occasions at least three weeks apart.

Complications and Prognosis of COPD

  • Complications include respiratory infections, pneumothorax, pulmonary hypertension, cor pulmonale, and respiratory failure.
  • Prognosis is variable and depends on the severity of airflow limitation, frequency of exacerbations, and comorbidities.