A 3-year-old boy is brought to the emergency department with a 6-hour history of sudden-onset cough and stridor after playing with peanuts. Chest X-ray shows hyperinflation of the right lung with mediastinal shift. Which clinical feature best distinguishes a foreign body lodged in the main bronchus from one impacted in the larynx?

## Distinguishing Laryngeal vs. Bronchial Foreign Body ### Anatomical Basis The location of foreign body aspiration determines the clinical presentation based on airway dynamics and obstruction pattern. ### Comparison Table | Feature | Laryngeal FB | Bronchial FB | |---------|--------------|-------------| | **Stridor type** | Inspiratory (fixed obstruction) | Expiratory or absent | | **Chest X-ray** | Normal or mild changes | Unilateral hyperinflation, mediastinal shift | | **Air entry** | Bilateral, often equal | Unilateral decreased | | **Cough character** | Barking, seal-like | Persistent, paroxysmal | | **Dysphagia** | Present (laryngeal irritation) | Absent | | **Onset** | Acute respiratory distress | May be delayed presentation | **Key Point:** Unilateral hyperinflation with mediastinal shift on chest X-ray is the hallmark of bronchial foreign body. This occurs because the foreign body acts as a one-way valve — air enters distal to the obstruction during inspiration but cannot exit during expiration, causing air trapping and hyperinflation on that side. ### Clinical Pearl A child with a bronchial FB may present with a history of "resolved" aspiration event because initial stridor subsides once the FB passes the larynx. The hyperinflation finding on imaging is often the key diagnostic clue. **High-Yield:** In laryngeal FB, inspiratory stridor dominates because the obstruction is fixed and narrows the airway during the inspiratory phase when negative intraluminal pressure is greatest. In bronchial FB, the obstruction is dynamic (check-valve mechanism), producing expiratory obstruction or minimal stridor but prominent air-trapping on imaging. ### Mnemonic **LARYNX = Inspiratory stridor; BRONCHUS = X-ray hyperinflation** — Laryngeal obstruction → fixed, inspiratory stridor — Bronchial obstruction → dynamic (check-valve), hyperinflation on CXR