Pulmonary interstitial emphysema (PIE), seen predominantly in premature infants on prolonged ventilation, is commonly a sequela of which process?

• A. Barotrauma
• B. Inadequate ventilation
• C. Pulmonary hypoplasia
• D. Pulmonary edema

Answer: (A)

PIE arises when air leaks into the lung interstitium as a result of overdistension from positive-pressure ventilation. The fragile, underdeveloped airways of premature infants are especially vulnerable to high transpulmonary pressures, causing alveolar rupture and air tracking along the bronchovascular bundles into the interstitial tissues. This barotrauma—and the accompanying volutrauma from prolonged ventilation—produces the characteristic interstitial lucencies on imaging and can lead to pneumothorax or pneumomediastinum if the air dissects further.

Inadequate ventilation would cause impaired gas exchange without producing this air-leak phenomenon. Pulmonary hypoplasia involves underdeveloped lungs with reduced alveolar surface area, not air escaping into the interstitium. Pulmonary edema is fluid-related, not air-related, and does not produce interstitial air leaks.