Reply to Risk factors for pulmonary interstitial emphysema in the preterm infant: still more challenges than answers.

We thank for the opportunity to respond to the letter of Dr. Al-Abdi (1) concerning our manuscript "Preeclampsia was a risk factor for pulmonary interstitial emphysema (PIE) in preterm infants born ≤ 32 weeks of gestational age" (2). We like to comment on the chronology and scientific facts. The case report by Al-Abdi et al is within a series of PIE in infants on non-invasive ventilation (NIV) and we added two additional cases (3,4). These observations permit the conclusion that PIE can occur during NIV what is contradictory to the long-lasting assumption that PIE is caused by high ventilation pressures or tidal volumes.