Emphysema Interstitial emphysema 2020-04-25T12:44:03Z Interstitial emphysema is characterized by air dissecting within the interstitium of the lung, typically in the peribronchovascular sheaths, interlobular septa, and visceral pleura. It is most commonly seen in neonates receiving mechanical ventilation. It is rarely recognized radiographically in adults and is infrequently seen on CT scans. It appears as perivascular lucent or low attenuating halos and small cysts.