A four-year-old dachshund named Trevor ballooned to three times his size when an injury caused him to fill with air.

His owners, Francine and Jessica Jennings from Cheshire in the United Kingdom, came downstairs one morning to find the normally tiny Trevor distressed and inflated.

"His head and his neck all merged into one, so he was just like a super fat seal" Jessica told the BBC.

"When we picked him up he felt full of air … and he crackled like bubble wrap underneath your fingers," Francine added.

Francine rushed Trevor to the emergency vet when it became clear the dog was suffering from breathing difficulties.

"I was shocked, but really, really worried because I didn't know what it was or where it had come from," Jessica said.

X-rays showed trapped air was causing Trevor's skin to lift away from his body.

Little Trevor the Dachshund was in high spirits again after his operation. ( Facebook: Willows Vet Group )

Tests were carried out and the dog was diagnosed with sub-cutaneous emphysema, an abnormal collection of air under the skin.

An open wound can cause air to become trapped between the layers of skin and, in turn, cause the bubble wrap feeling reported by dog owners.

In most cases if there is not infection the air will gradually absorb on its own — but Trevor's case required immediate action.

Vet Michelle Coward at the Beech House surgery in Warrington told the BBC she had never seen a case like this before.

"There were no external injuries that would explain how air had got under the skin, so we suspected that an internal injury to the airway could have been allowing the air in," Dr Coward said.

The team of vets were able to determine he had an injury to his windpipe, but it is still not clear how Trevor's windpipe was hurt.

Jessica and Francine said that since his surgery, Trevor has returned to normal and spends his day chasing the chickens on their property.