First aid and CPR training

It works if there is someone unconscious next to you and an ambulance on the way. It is the measure with the hardest evidence on this whole list and it has nothing to do with AI: in 30,381 witnessed out-of-hospital cardiac arrests in Sweden between 1990 and 2011, 10.5% were still alive at 30 days when somebody performed CPR before the emergency services arrived, against 4.0% when nobody did. Adjusted by propensity score, the odds ratio is 2.15, with a 95% confidence intervalConfidence intervalThe range within which the true value probably lies, given what was measured. The wider it is, the less precise the measurement. It is abbreviated CI.For exampleLike saying you will arrive “between 7 and 7:20”: you do not know the exact minute, but you do know the margin. between 1.88 and 2.45 ^[498]Early cardiopulmonary resuscitation in out-of-hospital cardiac arrestHasselqvist-Ax, Ingela; Riva, Gabriel; Herlitz, Johan et al. · 2015 · paperView source ↗verified through CrossrefAccessed on 9 September 2026.

It does not work if the problem is systemic. No scenario on this site stops because more people know CPR.

Evidence. Large, longitudinal, with an effect sustained over two decades and with a hard outcome. It comes from another field, and that is why it is solid.

Cost. A short course, once, with a refresher every so often.

What it does NOT solve. Nothing structural. Its best argument is also the most modest one: it pays off next Tuesday, without any catastrophe happening, and that is a bar almost no other measure on this list clears. If you are going to do one single thing from here and you do not depend on a medical device, this is probably it.