I’ve done expeditions with both insulin pumps and injections. Some more information on your background experience with similar activity levels would be helpful – have you ever done long runs or hiking?
You’ll find your basal levels will fall, possibly significantly. Your insulin sensitivity will be greater, so your ratio of bolus-to-drop-in-BG will increase, and your ratio of I:C will drop.
I have not experienced problems with changes in my insulin sensitivity because of altitude (over 15,000 feet), but everyone reacts differently to altitude so be cautious. However — your vials of insulin have air in them, so you can get a big pressure gradient between the vial and outside, and this can surprise you. Remember to use the valve that connects your reservoirs to your vial of insulin, to release the pressure gradient (connect it to the vial only so air can flow through the needle freely).
I saw the comment about using cold packs to protect your insulin. This myth is a legacy from pharmaceutical history. I’ve had insulin unprotected in 120 degree weather for days on end without ever a spoilage, and in fact I’ve lived this way a lot of the time. HOWEVER I have lost insulin to freezing. In my experience that’s much more of a danger. On expeditions, I’ve had to take all my insulin and remember to carry it in inside pockets, against my body, to protect it from cold. Same with glucometer, your glucometer can stop working from the cold.
Enough for now…