| Classification | Description | Notes |
| Type 1 | Parenchymal round cavity air or air/fluid-filled | Barotrauma |
| Type 2 | Paravertebral ovoid cavity, air or air/fluid-filled | Shearing injury of lung against vertebra |
| Type 3 | Peripheral cavity, deep to rib fracture | Generally associated with pneumothorax |
| Type 4 | Associated with prior adhesions | Diagnosed only at surgery or autopsy |
References:
Wagner, R. B., et al. (1988). “Classification of parenchymal injuries of the lung.” Radiology 167(1): 77-82.