I have been at high altitude a few times before and know what you are talking about. Not fun to gasp for air when there is none. It has never been a problem before, you get winded a little quicker. I always hit the stair climber hard about 3 months before we leave and that helps with the endurance. We have done quite a bit of mule deer hunting
in wyoming around Rawlings/Encampment area. So the elevation should not be too much of a problem.