Acute bronchitis is an inflammation of the bronchial mucosa due to infection by pathogens such as viruses or bacteria. It is a common and frequent disease in infants and children, often secondary to upper respiratory tract infections, and is often an early manifestation of pneumonia. The disease mostly involves both trachea and bronchus, so the correct name should be acute tracheobronchitis. It is characterized clinically by a cough with (or without) increased bronchial secretions.
Infection
The viruses that cause this disease include adenovirus, influenza virus, respiratory syncytial virus, and parainfluenza virus; the bacteria include Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus, and Staphylococcus. Viruses and bacteria can directly infect the trachea-bronchus, or they can first invade the upper respiratory tract and then cause the disease. In recent years, the number of cases caused by mycoplasma and chlamydia has been increasing.
Physical and chemical irritation
Inhalation of cold air, dust, irritant gases or fumes (such as sulfur dioxide, nitrogen dioxide, ammonia, chlorine, ozone, etc.) can cause acute inflammation of the tracheobronchial mucosa.
Metamorphic reaction
Common allergens that cause tracheal and bronchial allergic reactions include pollen, organic dust, bacterial proteins, fungal spores, and larvae of hookworms and roundworms that migrate in the lungs.
Clinical manifestations
Acute infectious bronchitis is often preceded by symptoms of acute upper respiratory tract infection: nasal congestion, malaise, chills, low-grade fever, back and muscle pain, and sore throat. The appearance of a severe cough is usually a sign of the appearance of bronchitis. It starts with a dry cough without sputum, but after a few hours or days a small amount of mucous sputum appears, and later on more mucus or mucopurulent sputum appears. Obvious purulent sputum suggests multiple bacterial infections. Some patients have burning retrosternal pain that is aggravated by coughing. In severe cases without complications, fever of 38.3 to 38.8°C may persist for 3 to 5 days. The acute symptoms then disappear (although the cough may continue for several weeks). Persistent fever suggests a combination of pneumonia. Respiratory distress secondary to airway obstruction may occur.
Acute bronchitis without comorbidities has almost no pulmonary signs. Severe complications are usually seen only in patients with underlying chronic respiratory disease. Acute bronchitis in these patients can result in severe blood gas abnormalities (acute respiratory failure).
Examination
Chest x-ray
Thickened or normal lung texture, occasionally with thickened hilar shadow.
Blood biochemical examination
Peripheral blood leukocyte count is normal or low, with elevated total leukocyte count and neutrophilia when caused by bacteria or in combination with bacterial infection.
Diagnosis
Diagnosis is usually made on the basis of symptoms and signs, but if the disease is severe or prolonged, a chest X-ray is indicated to rule out other diseases or comorbidities. When severe underlying chronic respiratory disease is present, arterial blood gas analysis should be monitored. Sputum Gram stain and culture should be performed to identify the causative organism in patients who have failed antibiotic therapy or who have special conditions (e.g., immunosuppression).
Treatment
Patients should rest until their body temperature is normal. Patients should be encouraged to drink water during fever. Antipyretics (e.g., aspirin or acetaminophen for adults; acetaminophen for children) may relieve discomfort and lower body temperature.
Antibiotics should be used in the presence of COPD, purulent sputum or persistent high fever and in severe cases. For most adult patients, oral tetracycline or ampicillin is the effective drug of choice, with TMP-SMX as an alternative treatment. tetracycline is contraindicated in children <8 years of age, and amoxicillin may be given. Sputum smear and culture should be performed when symptoms persist or recur, or when the disease is unusually severe. Antibiotics are then selected based on the predominant pathogen and its drug sensitivity test. If the causative agent is Mycoplasma pneumoniae or Chlamydia pneumoniae, erythromycin may be given. During an influenza virus A pandemic, treatment with amantadine hydrochloride may be considered.