The Man in the Plastic Mask

I know I’m exposing my ignorance of DC folkways here, but I’m curious: who’s the dude in the picture on the right, taken during yesterday’s Chuck Hagel hearings? Interpreter? Message passer-alonger? Stenographer? Someone who needed a hit of oxygen to stay awake while John McCain was droning on? What’s the deal here?

UPDATE: The consensus in comments so far seems to be that this is a stenographer’s mask. You can read all about it here.