A newborn delivered at 40 weeks gestation has thick, green-stained amniotic fluid noted at delivery. The infant is now 2 hours old and exhibiting signs of respiratory distress. Which assessment finding would be MOST indicative of meconium aspiration syndrome?

In a term newborn with meconium-stained amniotic fluid and respiratory distress, a systematic physical assessment is critical to detect air leak syndromes. Asymmetrical chest expansion with decreased breath sounds on one side is the hallmark of a pneumothorax, a life-threatening complication of MAS.

• Inspection: Observe for asymmetrical chest wall movement. The affected side will lag or appear larger and less mobile compared to the unaffected side.
• Auscultation: Listen for decreased or absent breath sounds on the affected side. This finding, combined with asymmetry, strongly suggests air in the pleural space collapsing the lung.
• Palpation and Percussion: You may find a shift in the point of maximal impulse (PMI) away from the pneumothorax side. Hyperresonance on percussion is a classic but less commonly relied-upon finding in noisy NICU environments.
• Transillumination: A high-intensity cold light placed on the chest wall can rapidly identify a large pneumothorax, showing increased light transmission on the affected side. This is a quick bedside adjunct, but definitive diagnosis requires a chest radiograph.
• Immediate Action: If a tension pneumothorax is suspected (evidenced by severe distress, cyanosis, and hemodynamic instability), immediate needle decompression is required before radiographic confirmation.