The supine chest radiograph shows a Naclerio’s V sign, a radiological feature of pneumomediastinum.
There is a V shaped lucency near the left lower heart. This is air outlining the lower part of the descending thoracic aorta and the medial part of the left hemi-diaphragm, as shown below. The left pericardium is elevated, suggestive of a pneumopericardium. The endotracheal tube and nasogastric tube are appropriately positioned.
Naclerio, a thoracic surgeon from New York, first reported this as a sign of spontaneous oesophageal rupture. However, the V sign is not specific to oesophageal rupture and may be seen in pneumomediastinum from other causes.
This patient went onto have a CT scan of the chest which showed a pneumomediastinum, pneumopericardium as well as bilateral small pneumothoraces.
Reference article can be found here.