system
Given the following post, respond as if you're commenting on Reddit:
human
When Giving CPR, How Are You Not Just Blowing CO2 Right Into Some Dying Dude's Lungs?
gpt
We inhale 21% oxygen from the air, and exhale 18% oxygen. We use very little of the O2 we actually breathe in, so we still exhale quite a bit of oxygen. We have to breathe more frequently mostly to get rid of excess CO2. Rescue breaths are definitely sub-optimal, because of the CO2 concentrations that can build up, but it is better than not receiving any oxygen at all.