Acute bronchitis

Causes and classification

The overwhelming majority of cases (about 90%) represent a clinical manifestation of acute respiratory viral infections (ARVI). The leading pathogens include respiratory syncytial virus, influenza and parainfluenza viruses, adenoviruses, as well as rhinoviruses and bocaviruses. Bacterial flora triggers the disease in less than 10% of cases. Primary bacterial bronchitis is rare and is usually associated with atypical pathogens (Mycoplasma pneumoniae, less commonly Chlamydophila pneumoniae).

Secondary bacterial infection with typical flora (Streptococcus pneumoniae, Haemophilus influenzae) occurs against the background of reduced local resistance and impaired mucociliary clearance. Contributing factors include passive smoking, allergic background, air pollutants, or gastroesophageal reflux.

Depending on the clinical course, three main forms are distinguished:

• Acute simple bronchitis — a classic course with no signs of airway obstruction.
• Acute obstructive bronchitis — inflammation proceeding with diffuse impairment of bronchial patency.
• Recurrent bronchitis — a form in which acute episodes recur 2–3 times or more per year, typically following ARVI.

Mechanisms of inflammation development

Pathogenesis starts with the infectious agent exhibiting tropism for respiratory epithelial cells. The pathogen causes local mucosal hyperemia, leading to desquamation of the damaged epithelium. Following this, edema and leukocyte infiltration increase in the submucosa. The final stage is the production of abundant pathological secretion, which may be mucous or mucopurulent.

In children under five years of age, inflammation is frequently complicated by bronchial obstruction syndrome. Impaired airway patency is caused by three factors: inflammatory edema of the bronchial wall, hypersecretion of excessively viscous mucus, and spasm of the bronchial smooth muscle.

Clinical presentation

The disease rarely occurs in isolation; as part of downward infection, it is frequently combined with rhinosinusitis, pharyngitis, or tracheitis. The general infectious syndrome manifests as low-grade fever and tachypnea.

The key symptom is a cough that undergoes a characteristic evolution:

1. Onset: in the first few days, the cough is dry, frequent, and non-productive.
2. Peak: a few days later, the cough becomes productive (wet) and sputum begins to be expectorated.

Intensive coughing fits can induce vomiting (especially when children swallow mucus) and a burning sensation behind the sternum. Auscultation reveals scattered dry and moist (medium and coarse bubbling) rales.

In obstructive bronchitis, signs of respiratory impairment come to the fore: expiratory dyspnea (difficulty exhaling) and distant wheezing appear. Visually, accessory muscles can be seen participating in the act of breathing, and upon auscultation, high-pitched wheezes dominate over moist rales.

Diagnostic algorithm

The diagnosis is established primarily based on the clinical presentation. Additional tests are required to clarify the etiology or rule out complications:

• Complete blood count: in a viral infection, lymphocytosis is characteristic against a background of normal or decreased leukocytes. A typical bacterial infection yields neutrophilic leukocytosis and an elevated ESR. Chlamydial etiology may be accompanied by eosinophilia, while mycoplasmal infection often presents with no specific changes.
• PCR and ELISA: are ordered strictly according to indications (severe course, poor premorbid background) to search for specific antigens, DNA, or RNA of pathogens.
• Chest X-ray: is used only for differential diagnosis, primarily to rule out pneumonia. In simple bronchitis, there are no infiltrates (only accentuation of the pulmonary pattern); in obstructive bronchitis, signs of increased lung lucency appear.

Children with obstruction are also indicated for pulmonary function testing (spirometry, bronchophonography).

Treatment approaches

Therapy is most often carried out on an outpatient basis. Hospitalization is indicated for young children with moderate to severe obstructive syndrome. Non-pharmacological measures play an important role: adequate hydration and postural drainage to stimulate sputum clearance.

Pharmacotherapy:

• Antibiotics: strictly not indicated for a viral etiology. They are prescribed only when a bacterial infection is highly likely or confirmed (aminopenicillins for typical flora, macrolides for atypical flora).
• Symptomatic agents: antipyretics (paracetamol, ibuprofen) for fever.
• Respiratory therapy: mucolytics (ambroxol, acetylcysteine) and herbal expectorants are used to thin sputum. Antitussive medications are prescribed exclusively for a dry, exhausting cough that disrupts sleep.
• Bronchodilators: inhaled drugs (salbutamol, fenoterol/ipratropium bromide) are indicated for the obstructive variant of the course.

Class and exam questions

What else to study on this topic

• Clinical and laboratory features of atypical pathogens (Mycoplasma, Chlamydophila)
• Physiology of mucociliary clearance and mechanisms of lung barrier function
• Spirometry and bronchophonography: assessing pulmonary function in children
• Differential diagnosis of recurrent bronchitis and cystic fibrosis
• Mechanism of action and rules for using mucolytics in pediatric practice

Other topics in "Chapter 4. Respiratory Diseases"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.