A New Zealand truck driver who inflated "like a balloon" when he fell buttocks-first onto a compressed air nozzle is being described as lucky to be alive.

While working on Saturday, Steven McCormack slipped between the cab and the trailer of his truck and was impaled in the thigh by a high-pressure air cylinder which saw his body pumped full of compressed air.

The 48-year-old Bay of Plenty truckie told the Whakatane Beacon he felt as if he was going to explode and began to scream as his neck, feet and hands swelled up.

"I was blowing up like a football... it felt like I had the bends, like in diving. I had no choice but just to lay there, blowing up like a balloon," he said.

Workmates rushed to Mr McCormack's aid, turning off the compressed air and packing ice around his swollen neck.

Ambulance officers removed the brass nozzle and rushed him to Whakatane Hospital, where a surgeon treated the injury and drained one of his lungs, which had filled with fluid during the ordeal.

Mr McCormack said doctors later told him that the air separated fat from muscle and they were surprised his skin did not burst.

Now recuperating, he told the Beacon his skin felt "like a pork roast", hard and crackly on the outside but soft underneath.

Treating surgeon Dr Barnaby Smith said by the time Mr McCormack arrived at the hospital, the gas had made its way from his thigh, into his abdominal cavity and chest.

"It even tracked as high as his eyelids - he couldn't open them because they were so swollen," he said.

"He did have gas within the chest cavity compressing the lungs and heart."

Emergency surgery helped relieve the pressure on Mr McCormack's heart and lungs.

"It's not in the textbooks, and it's the first time anyone I know has seen it as well," Dr Smith said.

A hospital spokeswoman said it could have killed Mr McCormack.

"It's fair to say he's lucky to be alive, it was a potentially life-threatening situation," she said.

Dr Smith said Mr McCormack had almost shrunk back to his normal size.

- ABC/AFP