[This version of Bucky Barnes doesn't know Tony Stark. Not yet, anyway. Winter twitches aside the instant before Tony's wheelchair actually hits him, giving him a wary kind of look which Tony may or may not interpret as recognizing him and expecting anger.

Mostly he just isn't sure why he was being "attacked" with a wheelchair.

He says, after a pause, voice oddly uninflected:]

I don't think you're dying.