Bunch of great advice in this forum.
My two cents.
1) A good safety talk at the beginning of an outing. Including an opportunity to disclose pre-existing conditions or medical wishes.
2) For extended trips I'll carry a bag valve mask, BP cuff/stethoscope, and Pulse Ox. I like the advise that whatever you carry should be things you know how to use, these are my main tools at work so they are things I feel comfortable using in an emergency. For extended trips I want a toolset that allows me to make decisions about severity and urgency ( blood pressure and oxygenation are a good start). And the bag valve mask for extended trips because if breathing is a concern, mouth to mouth becomes pretty impractical after about an hour.
3) In reality the things I actually tend to use are syringes for pressure washing cuts, herbal antimicrobials for early intervention of infection or food poisoning (oregon grape, huang lian san, et.c.), and assorted pain and bowel meds.