Bronchitis and Bronchiolitis

Study Notes

Bronchitis is an inflammatory condition of the large elements of the tracheobronchial tree, affecting older children and adults.
Bronchiolitis is an inflammatory condition of the small elements of the tracheobronchial tree, mostly affecting infants during their first year of life.

Infection of the trachea and bronchi leads to hyperemic and edematous membranes, increased bronchial secretions, and damage to the respiratory epithelium.
Chronic inhalation of an irritating substance compromises the normal secretory and mucociliary function of bronchial mucosa, leading to thickening of the bronchial wall.
Increased desquamated epithelial cells and bronchial secretions may impair mucociliary actions, and goblet cells in smaller bronchi produce more mucus.

Viruses are the most common cause of acute bronchitis, including rhinovirus, coronavirus, influenza virus, and adenovirus.
Bacterial causes of acute bronchitis include Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Bordetella pertussis.
Acute exacerbations of chronic bronchitis are often caused by H. influenzae, M. catarrhalis, S. pneumonia, and Gram-negative pathogens.
Secondary bacterial infections may occur after a viral infection.

Symptoms include nonproductive cough early, followed by productive mucopurulent sputum, and fever is rare.
Purulent sputum is off-white, yellow, or green, and opaque, indicating the presence of large numbers of white blood cells.
Red coloration of sputum is usually due to its mixture with blood.
More pronounced symptoms occur in patients with underlying lung disease.

Mild to moderate cough with increased sputum production for at least 3 consecutive months for 2 years is characteristic of chronic bronchitis.
Simple chronic bronchitis is diagnosed when there are no major risk factors and sputum flora reflects the common associated pathogens.
Complicated chronic bronchitis is described when patients have two or more disease-associated risk factors, including FEV1, home oxygen use, underlying cardiac disease, use of immunosuppressant, and use of antibiotics for an exacerbation within the past 3 months.