I almost always get nausea at about 12,500, too, and if I can remain calm & push past it, I find that I sometimes feel better at 13,000 than I did at 12,000. Switchbacks require a lot of exertion, too, so I think that pairing that combo of switchies and elevation is a "winner" (loser??) I had the same thing happen on the switchbacks on the way up to Mono Pass (Mosquito Flat trail) and I found that I could almost talk myself out of getting worse by remembering that I had done my "homework", so that I would not get sick (and I did not)
