system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is no mouth CPR what everyone is told to do now?

Is it because an untrained person will do it wrong, or are the breaths simply not worth doing? When I was trained to do CPR it was with breaths so should i just not do them now?
gpt
The breaths aren't worth doing. Keeping the heart pumping (doing the compressions) is far more important. This is because while people will lose consciousness from carbon dioxide build up in a couple of minutes, the average person actually has enough oxygen in their blood to stay alive for for a while (nearly 20 minutes) if the heart is pumping. There's really a caveat that after about ten minutes you need to start doing rescue breaths if they're not breathing. But the idea is that in most "man on the street" rescue efforts professionals show up and take over before the person would actually die of lack of oxygen. So for an amateur trying to operate in a high stress situation they probably aren't super practiced in, keep it as simple as possible to have the best effect. Add to that rescue breathes don't have much oxygen in them anyways, since your lungs filtered it out when you inhaled.