Chronic Bronchitis Diagnosis and Pathophysiology

Diagnosis of Chronic Bronchitis

• Characterized by a cough productive of sputum for over three months' duration during two consecutive years and the presence of airflow obstruction
• Pulmonary function testing aids in the diagnosis by documenting the extent of reversibility of airflow obstruction

Pathophysiology of Chronic Bronchitis

• Airflow obstruction is caused by excessive tracheobronchial mucus production
• Distinct from the anatomic findings of distal air space distention and alveolar septa destruction, which define emphysema

Risk Factors

• Cigarette smoking is the most important risk factor for the development of chronic bronchitis
• Over 90% of patients with chronic bronchitis have a smoking history

Mortality Rate

• The overall 10-year mortality rate following the diagnosis of chronic bronchitis is 50%

Acute Exacerbations

• Often precipitated by bacterial infection, manifested by purulent sputum, fever, and a worsening of symptoms
• Other known precipitants include viral upper respiratory infections, seasonal changes in the weather, medications, and exposure to irritant inhalants

Bacterial Pathogens

• Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are the three leading bacterial pathogens isolated from the lower bronchi of patients with chronic bronchitis

Management of Chronic Bronchitis

• Inhaled ipratropium bromide and sympathomimetic agents are the current mainstays of management
• Oral steroid therapy should be reserved for use in patients with demonstrated improvement in airflow not achievable with inhaled agents
• Antibiotics play a role in acute exacerbations, but have been shown to lead to only modest airflow improvement
• Strengthening of the respiratory muscles, smoking cessation, supplemental oxygen, hydration, and nutritional support also play key roles in long-term management

Pulmonary Function Testing

• Documentation of airflow obstruction by pulmonary function testing is critical for the diagnosis of chronic bronchitis
• A measured forced expiratory volume in one second (FEV1) of less than 70% of the total forced vital capacity (FVC) defines obstructive airway disease

Smoking Cessation

• The single most effective way to reduce the risk of future morbidity from chronic bronchitis
• Use of various smoking cessation tools, such as nicotine replacement systems, behavior modification training, and support groups, can be helpful

Pharmacologic Management

• Inhaled anticholinergic or anti-inflammatory agents, such as ipratropium bromide and sympathomimetic agents, are the mainstays of therapy
• Theophylline has a narrow therapeutic range and relatively common medication interactions, limiting its use
• Steroids can be delivered by inhalation or systemic therapy, but long-term oral steroid therapy should be reserved for use in patients with documented symptomatic improvement in airflow not achievable with inhaled preparations### Pulmonary Rehabilitation
• Training inspiratory muscles against progressive resistance loads improves exercise tolerance, especially when combined with abdominal breathing exercises to reduce thoracic respiratory muscle fatigue.

Nutritional Support

• Increased respiratory muscle work during pulmonary rehabilitation requires enhanced nutritional support.

Hydration and Sputum Mobilization

• Improved hydration through increased fluid intake and airway humidity facilitates sputum mobilization more effectively than pharmacologic expectorants or mucolytic agents.

Chronic Obstructive Pulmonary Disease (COPD)

• The American Thoracic Society has established standards for the diagnosis and care of patients with COPD.

Chronic Bronchitis

• Smoking cessation reduces airway inflammation in chronic bronchitis.
• Haemophilus influenzae and Streptococcus pneumoniae are often associated with chronic bronchitis during acute exacerbations.
• Elevated substance P content is found in induced sputum from patients with chronic bronchitis.

Inflammation and Immune Response

• Bronchial inflammation in chronic bronchitis is characterized by increased cell products in bronchial lavage fluid.
• Haemophilus influenzae releases histamine and enhances histamine release from human bronchoalveolar cells.