**Core Concept**
Foreign body aspiration in children, especially under 6 years, often causes airway obstruction due to the immature airway anatomy and weak cough reflex. Immediate airway clearance is critical to prevent hypoxia and respiratory failure.

**Why the Correct Answer is Right**
In a child with a foreign body in the trachea, the first-line management is **Heimlich’s maneuver** (abdominal thrusts), which creates a sudden increase in intra-abdominal pressure to expel the obstructing object. It is effective in children over 1 year of age and is a recommended first-line action before advanced airway interventions. The maneuver works by generating a forceful upward push on the diaphragm, forcing air out of the lungs and potentially dislodging the foreign body.

**Why Each Wrong Option is Incorrect**
Option B: Cardiac massage is incorrect because it is used in cardiac arrest, not in a case of airway obstruction. The child has not lost consciousness or has no pulse, so CPR is not indicated initially.
Option C: Intubation is not the first step in a conscious child with a foreign body; it is a last-resort procedure requiring advanced training and is riskier than Heimlich’s maneuver.
Option D: Oxygen mask with IPPV (intermittent positive pressure ventilation) is ineffective in a child with a complete airway obstruction and may worsen the situation by increasing airway pressure and risk of aspiration.

**Clinical Pearl / High-Yield Fact**
In children under 6 years with a suspected foreign body airway obstruction, **Heimlich’s maneuver is the best initial action**—it is simple, fast, and effective. If the child becomes unconscious or unresponsive, then CPR and advanced airway management should be initiated.

✓ Correct Answer: A. Heimlich's maneuver