In a heart attack or cardiac arrest situation, EMTs will hook the guy up to high-flow oxygen immediately upon arrival. Question is ...?

Whatever you say libtard

With impurities do you mean extremely small amounts of nitrogen and co2 and other gases? That won't affect the outcome as long as they get the oxygen.

Why oxygen? Who needs oxygen?? Give him two-for-one chicken from the grocery store ;)

Legally it may not be a great idea, practically it could be a good idea. Depends on the manufacturer, but USP gases may be less pure than industrial grade, but USP puts limits on the amount of carbon monoxide tolerated (<0.001%) in gases other than oxygen. So if industrial oxygen is 99.5% pure vs. USP 99%, the question is how much of the 0.5% in industrial gas is CO, and would that offset the benefit of administering oxygen in the first place? The answer is likely no, since the CO would likely react with the abundance of oxygen to produce CO2 somewhere along the processing chain, which is probably why CO% is not listed for USP oxygen like it is for N2 and noble gases. That said, we don't really know. So the question remains, "Is this the type of person who will sue me if I save their their life?" For what it's worth, I use industrial grade CO2 for all of my kegging equipment, and I haven't grown a third arm yet. Which is too bad, because that would be useful as hell. Obviously this is not medical advice, and no recommendation is expressed or implied.

Running around looking for oxygen may not be that helpful over good CPR and 911. You could I suppose use it as a blow by but it comes out to hard to hook up to anything, could blow out a lung and get you actually into trouble as that is NOT prudent layperson.

There is no difference in the oxygen that is medical and industrial. The issue is that administering oxygen is considered a medical procedure and it is a crime if you are not in the medical field to administer oxygen to another person.

you can't be as totally sure if there's no contaminants in the welding oxygen as with the medical stuff

but depending on the situation and what they knew about their oxygen tanks i could totally understand somebody giving that a try