The DNR has both a large page form and a wallet size form. The wallet size is actually a bit large for a wallet... but EMTs are not allowed to go into your wallet to look for it. So... make sure that those you are with know about your wallet DNR so they can get it for EMT
Many have a DNR who are not at all ill. The data on successful outcome meaning survival without major brain damage of out of hospital CPR is grim, It is not unreasonable to elect to let nature take its course in the event of a full cardiac arrest rather than chance being "saved" then dealing with brain damage.
Overall survival and brain death frequency following out-of-hospital cardiac arrest - PMC
Of 130 arrests only 6 did not die or have significant damage.