Well, I certainly didn't. In training (military) I did a pressure chamber day with 33,000ft breathing (lots of fun, do it if you ever get the chance). They took us to 12,000 in a big chamber and then fed us a reduced oxygen via masks to simulate 33,000ft. After about a minute I certainly felt effects, but I was very much awake long long after 15 seconds. I was playing solitaire on an iPad thing. After everyone noticed their personal symptoms they switched us over to pure O2. Some experienced tunnel vision and such. All I ever felt was as slight headache and that I was doing worse at the ipad game. I was awake enough to remember the Sargent who walked up and down the chamber looking us in the eye to see if we were awake. He was scary.