Do any changes in either temperature or cooking times need to be made when cooking at higher elevations?
You know, I was thinking that your cooking time may need to be prolonged - not the temperature, as that’s a constant, but the density of water at higher elevations is less, due to the reduced atmospheric pressure (also causing it to have a lower boiling point).
Turns out your question was already asked over on Modernist Cooking in May: http://www.modernistcookingmadeeasy.com/how-to/sous-vide-for-high-altitude and answered by one of their members that sous vide in Colorado. Their answer was no, you really don’t need to make any alterations. It’s probable that the reduction in the density of the water isn’t enough to affect the cooking time (especially for longer cooks, where you have a considerably greater margin for error) 
One caveat though - if you need to do your cook at a temperature that actually is your local boiling point (or above it), that would definitely affect your cooking time. (if that were the case, I’d likely look at an alternate means to preparing that item).
Thank you very much! I truly appreciate your thoughtful, thorough response.