Here’s a good article on human acclimatization to high altitude: http://www.elbrus.org/eng1/high_altitude1.htm
"Start out sleeping at altitudes below 10,000 feet and spend two to three nights there before going higher. For every 2,000 to 3,000 feet gained, plan to spend an extra night acclimatizing to the new altitude.
“Climb high and sleep low. It is best not to increase the sleeping altitude by more then 2,000 feet at a time. Set up camp at lower elevations and take day trips to high points. Ferry loads up to a high camp and then return to the low camp to sleep as you acclimatize.”
This same acclimatization regimen should work for dogs, too. Hydration is also extremely important. However, the high-carb diet recommended for humans may not be the best thing for your dog.
grannyhiker