Interstitial emphysema

**Definition:** This is a collection of air outside of the normal air passages in the body and instead is found inside the connective tissue of the peribronchovascular sheaths, interlobular septa, and visceral pleura. This collection develops as a result of alveolar and terminal bronchiolar rupture.

**Exclusions:** - surgical subcutaneous emphysema - emphysema NOS - surgical emphysema - Traumatic subcutaneous emphysema, not elsewhere classified