If you look at the “Field Chart” Field Chart at around 29C with “slow pulse and breathing” the recommendation is to assist with rescue breathing.

I do not think a person who is not semi-conscious or unconscious is going to tolerate mouth-to-mouth breathing very well. It is also very tiring to the “rescuer” to perform this for any significant length of time.

If the patient/victim is breathing adequately on their own, I would suggest using some type of permeable cloth/bandana/etc. over the mouth/nose (make sure to monitor closely) that would allow the patient’/victim’s own breath to moisturize the material. Then having them in a warm environment should allow for warmed humid air to gradually warm the lungs or at least prevent/reduce further heat loss through respiration. One, could place a heat pack near the patient’s/victim’s mouth/nose to warm the air. If one has access to O2, wrapping the supply line around a heat pack and placing a saline moistened gauze pad in the mask should also help. I.V. solutions and I.V. lines can also be warmed with heat packs.

Pete