Pulmonary interstitial emphysema (PIE) is a condition characterized
by the abnormal accumulation of air within the interstitial tissue of
the lungs, outside the normal airways and alveoli. It most commonly
occurs in premature infants who are receiving mechanical
ventilation for respiratory distress syndrome, but it can also be seen
in adults with severe lung injury or overdistension of the lungs. The
pathogenesis involves air leaking from the alveoli into the interstitial
spaces due to alveolar rupture, often as a result of high ventilatory
pressures or overinflation. This trapped air can compress nearby
structures and disrupt normal gas exchange, leading to hypoxia and
respiratory distress. Diagnosis is made using chest X-rays or CT
scans, which show streaky, linear, or cyst-like air collections within
the lung interstitium
