Chronic Obstructive Pulmonary Disease

(=chronic obstructive airways disease)

Definition: Airway obstruction (FEV1/VC<70%) that does not change in severity over several months.

Mild: 60–70%; Moderate: 40–60%; Severe: <40%

Disability at 30%; Death at 15%.

COPD is a syndrome and not a disease. There are eleven causes:

  1. ephysema—smoking, α1-antitrypsin deficiency, &c.
  2. chronic obstructive bronchitis
  3. chronic irreversible asthma
  4. tracheal stenosis
  5. bronchiectasis—cystic fibrosis, hypogammaglobulinaemia, Kartagener's syndrome, &c.
  6. obstructive bronchiolitis—mineral dust inhalation, viral infection, connective tissue diseases, &c.
  7. byssinosis
  8. bronchopulmonary dysplasia
  9. histiocytosis X
  10. lymphangioleiomyomatosis
  11. sarcoidosis
  12. tuberculosis
Conventionally, COPD refers only to widespread obstruction of intrathoracic airways (so cause 4 is excluded), and "specific" causes of obstruction are also usually excluded (causes 5 to 12).

Chronic bronchitis

Definition: Chronic mucus hypersecretion sufficient to cause expectoration (in three consecutive months for at least two years). Diagnosis is clinical.

Emphysema

Definition: pathological dialation of the air spaces distal to the terminal bronchiole, with destruction of their walls and without obvious fibrosis. Diagnosis is by imaging and lung function tests.

Risk factors

  1. Smoking
  2. Increasing age
  3. Gender (M>F)
  4. Environmental pollution (urban>rural)
  5. Socioeconomic status (low status>high status)
  6. Occupation (Cadmium workers; coal & gold miners)
  7. Diet (fish and antioxidents possibly protective)
  8. Genetic factors (α1-antitrypsin deficiency)
  9. Low birthweight
  10. Childhood bronchiolitis

Natural history

Physiological hypoventilation during sleep→hypoxia (Douglas, 1979). More common in "blue bloaters" than "pink puffers". Patients with noctural hypoxaemia more likely to die at night.

Treatment