Six firefighters had to remove a window to get a 320kg woman out of her South Canterbury home.
It took the fire service two hours to cut the window out and then lift the woman and the mattress she was on into an ambulance.
The 54-year-old lives in a flat behind her father's house and relies on home help to care for her.
Canterbury Fire Service spokesperson Greg Crawford said such call outs are not uncommon. He said every month the fire service has to help St John Ambulance to lift patients.
"We now co-respond with ambulance to what they class their "purple calls" which is cardiac arrest and all that sort of stuff. So when people do report that type of event, it's more than likely that they will get an ambulance and a fire engine."