MELBOURNE teenager Ricky Petterd will remainin hospital for several days after one of his lungs collapsed duringhis side's win over Carlton at the MCG.

Club doctors had to inflate Petterd's lung after the 18-year-old ran- albeit slowly - from the field during the first quarter while havingtrouble breathing.

The Demons are unsure exactly what triggered the drama, but actingcoach Mark Riley admitted Petterd's condition was serious before thedoctors were able to get him breathing normally again.

"It was very, very bad and it was very touch and go there for a while," Riley said.