Frontal radiograph showing the most life-threatening finding of right-sided tension pneumothorax with left-sided mediastinal shift; this should be immediately decompressed. Extensive left-sided subcutaneous emphysema is also featured. However, another pertinent finding is of a well-defined structure over the left hemithorax midzone which appears to be 'lifted' off the left heart border. This is the Angel Wingangel wing or Spinnakerspinnaker sign representing the pediatric thymus in pneumomediastinum. 

Nasoenteric tube is correctly placed in the stomach. 

Certain plain radiographic signs of paediatric pneumomediastinum are unique compared to adults: Air

• air can lift the relatively large thymus gland off from the heart border to give the Angel Wingangel wing or Spinnakerspinnaker sign. Another
• another sign is air inferior to the mediastinum/superior to the diaphragmatic central tendon which can give the heart a conical appearance described as the Haystack sign after Monet's painting of the same name. 

These signs are important to be aware of in the young patient as paediatric pneumomediastinum can be otherwise occult. The

This case above represents an iatrogenic aetiology but a careful review of the case is usually required when there is no history of surgical intervention to establish a differential (e.g. infection, oesophageal perforation, etc.).

The Spinnakerspinnaker or Angel Wingangel wing sign should also not be confused with the Thymicthymic sail sign which refers to the pointy/triangular inferior edge of the thymus in normal cases.