USMLE Guide: Bronchitis

Introduction

Bronchitis is a common respiratory condition characterized by inflammation of the bronchial tubes, which are responsible for carrying air to and from the lungs. It can be acute or chronic, with acute bronchitis typically being caused by viral infections and chronic bronchitis often associated with smoking and long-term exposure to irritants. This guide aims to provide a comprehensive overview of bronchitis, covering its etiology, clinical features, diagnosis, and management.

Etiology

1. Acute Bronchitis:

   • Viral Infections: Acute bronchitis is predominantly caused by viral pathogens, such as rhinovirus, influenza virus, respiratory syncytial virus (RSV), and coronavirus.
   • Bacterial Infections: Although less common, bacterial pathogens like mycoplasma pneumoniae and bordetella pertussis can also lead to acute bronchitis.
   • Environmental Factors: Exposure to irritants like smoke, dust, or chemical fumes can trigger acute bronchitis.

2. Chronic Bronchitis:

   • Smoking: Cigarette smoking is the primary cause of chronic bronchitis. Prolonged exposure to tobacco smoke damages the bronchial lining, leading to chronic inflammation.
   • Environmental Factors: Long-term exposure to air pollution, occupational dust or chemicals can contribute to the development of chronic bronchitis.
   • Genetic Factors: Certain genetic conditions, such as alpha-1 antitrypsin deficiency, increase the risk of developing chronic bronchitis.

Clinical Features

1. Acute Bronchitis:

   • Cough: Persistent cough is the hallmark symptom of acute bronchitis, typically lasting for several weeks.
   • Sputum Production: Patients may experience clear, white, yellowish, or greenish phlegm production.
   • Sore Throat: Mild throat discomfort or irritation may be present.
   • Nasal Congestion: Some patients may report nasal congestion or rhinorrhea.
   • Low-grade Fever: Mild fever may be observed in certain cases.

2. Chronic Bronchitis:

   • Chronic Cough: Persistent cough with sputum production lasting for at least three months in two consecutive years.
   • Dyspnea: Shortness of breath or difficulty breathing upon exertion is common.
   • Wheezing: Wheezing sounds may be audible upon auscultation.
   • Cyanosis: Bluish discoloration of the lips or nail beds due to reduced oxygenation.
   • Frequent Respiratory Infections: Chronic bronchitis patients are more prone to recurrent respiratory infections.

Diagnosis

1. History and Physical Examination:

   • Detailed patient history and physical examination help assess the duration, severity, and potential causes of bronchitis symptoms.
   • Chronic bronchitis diagnosis requires a persistent cough with sputum production for at least three months in two consecutive years.

2. Laboratory Investigations:

   • Complete Blood Count (CBC): May reveal elevated white blood cell count in acute bronchitis, indicating an infectious process.
   • Sputum Culture: Recommended for chronic bronchitis patients to identify potential bacterial pathogens.
   • Pulmonary Function Tests (PFTs): Measure lung capacity and airflow, aiding in the diagnosis and evaluation of chronic bronchitis.

3. Imaging Studies:

   • Chest X-ray: May be performed to rule out other respiratory conditions and evaluate the extent of lung involvement in chronic bronchitis patients.

Management

1. Acute Bronchitis:

   • Supportive Care: Encourage rest, hydration, and symptomatic relief with over-the-counter analgesics, antipyretics, and cough suppressants.
   • Avoid Antibiotics: Acute bronchitis is primarily viral, and antibiotics are not recommended unless there is a secondary bacterial infection or high suspicion of pertussis.
   • Antiviral Medications: In specific viral infections like influenza, antiviral medications may be prescribed.

2. Chronic Bronchitis:

   • Smoking Cessation: The most crucial intervention. Encourage patients to quit smoking and provide appropriate resources.
   • Bronchodilators: Inhaled beta-agonists and anticholinergics help relieve bronchospasm and improve airflow.
   • Corticosteroids: Inhaled corticosteroids may be prescribed to reduce airway inflammation and prevent exacerbations.
   • Pulmonary Rehabilitation: A comprehensive program involving exercise, education, and support to improve quality of life and lung function.

Conclusion

Bronchitis