It really depends; some people with COPD do just fine at altitude and others really struggle. Ask your pulmonologist and take the High Altitude Simulation Test (HAST). That will give you an idea of how difficult or easy it will be for you.

I live at just over 3400 elevation., We took our trailer and went up to the Sierras, here in California, about 6000 Elev. It was extremely difficult to breathe. I find it takes a few days to kind of get use to it. When we go the the beach, I feel pretty good but we come home I need a few days to get use to our elevation. I feel sorry for my husband, because he loves fishing the High Sierra's but Its really not very enjoyable for me. I go and mostly hang out in camp close to my oxygen.

Thanks