Lots of basic classes out there, cpr, aed, basic first aid, basic triage etc.
Most courses are basics with the intention of teaching you how to keep someone alive until emts/paramedics arrive & take over then transport person to the hospital.
Check SOR training in moore (they do mostly security courses, but also have cpr, first aid, aed etc courses),
Also red cross, votechs etc do basic courses.
As posted above, a lot of "certified" instructors are former emts, paramedics, corpmen and some have real medical training but couldn't afford tuition anymore and dropped out to work in other fields of study.
I have basic cpr/aed/first aid/triage certs because places I worked it was required & training was from certified instructors.
You do cpr correctly on someone, you will crack some of their ribs and you will know quick how out of shape you are cause your stamina will wear out fast.