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COPD (Chronic Obstructive Pulmonary Disease)

Definition

  • Lung obstruction, commonly encompassing chronic bronchitis and emphysema
  • Almost always caused by smoking

 

Risk factors

  • Smoking
    • >20 pack year smoking history
  • Low SES
  • Increased age
  • High pollution exposure including particulates such as paint or flour

 

Differential diagnosis

  • Pneumonia
  • Lung cancer
  • Asthma
  • Bronchiectasis
  • Bronchiolitis
  • TB
  • Heart failure/pulmonary oedema
  • Mesothelioma

 

Epidemiology

  • 5th leading cause of death and disability worldwide
  • More common in those over 65
  • More common in men
  • More common in white people

 

Aetiology

  • 90% of COPD cases are caused by smoking
    • Inflammatory response, fibrosis, epithelial damage
  • Air pollution and occupational exposure
  • α-1 antitrypsin deficiency can cause COPD at an early age

 

Clinical features

  • SOB on exertion (or at rest)
  • Reduced exercise tolerance
  • Productive (white or grey) cough
  • Barrel chest
  • Wheeze
  • Hyper-resonance
  • Hypoxia
  • Coarse crackles
  • Tachypnoea
  • Use of accessory muscles

 

Pathophysiology

  • Oxidative damage to α-1 antitrypsin, which reduces its inhibitory effect on elastase
  • This decreases the amount of elastin (as it is all digested by elastase)
  • Leads to destruction of alveoli – leading to emphysema (bullae and bigger airspaces)
  • Irritation of epithelia causes macrophage recruitment, and induces metaplasia
  • Ciliated epithelia become squamous epithelia, and fibroblasts appear
  • Hyperplasia of goblet cells and increased numbers of mucus glands
  • Immune response mediated by neutrophils and CD8+ (cytotoxic) cells
  • Leads to bronchitis

 

Investigations

  • Peak flow – reduced PEFR
  • Spirometry – bronchitis will show obstructive pattern (FEV1 < 80% predicted, FEV1% less than 70%), whereas emphysema may show restrictive pattern (FVC <80% predicted, FEV1% >70%)
  • Pulse oximetry – reduced sats – aim for 88-92% in COPD patients
  • ABG – to check for respiratory failure: type 1 has low O2 but normal CO2. Type 2 has low O2 and high CO2
  • Increased resp rate
  • Sputum sample
  • CXR – may not show much – may be hyperinflated
  • All new diagnoses of COPD should have a CT scan to rule out more sinister causes

 

Management

  • Smoking cessation advice
  • Pulmonary rehab
  • Bronchodilators (as with asthma) – including beta 2 agonists
  • Theophylline and corticosteroids may be used in more advanced stages
  • Oxygen therapy for more advanced stages – aim for 88-92%

 

Prognosis

  • Depends on stage/severity, genetics, comorbidities, exacerbations
  • 5-year survival is not high, but not well documented
  • Only smoking cessation and oxygen therapy are proven to improve mortality
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