I had an unsedated upper endoscopy today in the US (where people are almost always sedated). Beforehand I was so scared that I cancelled four times, and was terribly preoccupied. But when I finally did it I wanted to kick myself for putting it off. It's very manageable. You can avoid gagging if you don't swallow, and even if you do gag (as I did when I made the mistake of swallowing) it's nothing like being sick or hung over - it's not that uncomfortable and isn't frightening. So don't be concerned that you will just gag uncontrollably - you can totally control what happens, and if you stay calm you will thank yourself for the clearheaded day that follows!