Lung sliding

In the absence of pneumothorax, the 2 pleural layers slide over each other creating series of comet tail artefacts. This is known as the LUNG SLIDING SIGN.

However when air sits in the pleural space (pneumothorax), no lung sliding is seen. This is referred to as ABSENT SLIDING SIGN.

Th junction between lung sliding and absent lung sliding is called the LUNG POINT.

Identification of this is near 100% specific for the presence of a pneumothorax.