There are four major types of lung overexpansion injuries, and the type that develops depends on where the expanding air escapes to.

The most serious lung injury is an arterial gas embolism. This occurs when air from the lungs escapes into the bloodstream. As the air expands and forms bubbles, it interferes with blood flow. Without immediate treatment, this injury can lead to death.

A pneumothorax occurs when air enters the space between the lung's two outer linings. As the air expands, it causes the lung to collapse, making breathing very difficult.