Chronic Bronchitis

Introduction

Defined as expectoration for > 3 months for > 2 consecutive years
Pathophysiology
- overproduction of mucus due to inflammation
- central and peripheral airways involved
- results in hyperplasia of bronchiolar mucus glands and fibrosis of terminal bronchioles
- ciliary dysfunction
Causes
- smoking
  - chronic irritation promotes hyperplasia of mucus glands and increases mucus production
  - toxicity of smoke destroys ciliated epithelium and replaces with squamous cells which ultimately reduces mucus clearance
- cystic fibrosis
loss of CFTR function results in increased viscosity of mucus and decreased mucus clearance

Presentation

Evaluation

Labs
- ABG during exacerbation shows hypoxemia and may show acute respiratory acidosis
  - hypoxemia can stimulate increased erythropoetin production by the kidneys
    - can see polycythemia with prolonged hypoxemia
- chronic respiratory acidosis
Chest radiograph
- cardiomegaly (horizontally oriented)
- increased bronchial markings (due to mucus)
Clinical diagnosis confirmed by lung biopsy (rarely indicated)
- ↑ Reid index
  - gland layer > 50% of total diameter of bronchial wall
    - bronchial wall measured from the surface epithelium to the beginning (but not including) the cartilaginous rings
- patch squamous metaplasia
- neutrophil infiltration
Pulmonary function tests
- hallmark is obstruction
- ↓ FEV / FVC
  - similar to emphysema
↑ TLC (less than emphysema)

Treatment

Complications

Pulmonary hypertension
- chronic alveolar hypoxia results in pulmonary vasoconstriction
  - right side ventricular hypertrophy and failure (cor pulmonale)
  - distended neck veins
  - hepatomegaly