– If humans breathe in oxygen and exhale CO2, then why does mouth-to-mouth resuscitation work?
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Others already talked about oxygen, but the other and more important part of CPR is that you’re helping sort of jump start the lungs by getting them to expand and contract, which can help with blockages and other stuff, but always remember to check the airway first.
Additionally the mouth to mouth part of cpr is falling slightly out of favor as chest compressions do all the heavy lifting.
You have a dollar. You go to buy a peice of candy for $0.25. You get your candy, and you also get $0.75 back.
The peice of candy is all you need, and as long as you buy it like this, you will always get most of your money back.
But one day, your friend is hungry. They skipped breakfast and now they are feeling dizzy. They need something to eat.
You need to eat, too, so you use the exact same dollar to buy your candy. Only this time, you use your leftover money to buy one for your friend as well.
You saved his life using the money you always had but never used to give him what both of you need.
When you breathe, you never use all of the oxygen. That’s the dollar. Most of it goes unused. In an emergency, you can use your leftover oxygen to help someone else.
HOWEVER
mouth to mouth isn’t taught anymore. It’s known that if someone’s heart stops, there is still enough oxygen to last them several minutes. The problem is, the brain needs it the most, and the blood isn’t moving. So the oxygen in the blood around the brain gets used up.
The key to Saving them is chest chest compressions to help the heart pump blood to get fresh blood to the brain. No breathing required.
The risk to benefit of breathing on someone’s mouth to BOTH them and you is undesirable, especially in these times of… Infection control or lack thereof.
Worry not about mouth to mouth and learn proper CPR technique.
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You do not breathe in oxygen and breathe out CO2. You breathe in air and breathe out air. Air has a varying degree of oxygen, CO2, nitrogen and other gases. The air you breathe out still has plenty of oxygen, just less than before
Short answer is we don’t really do that anymore.
In principle, it was OK because we breath in 21% o2 but only keep about 5% of thst, we exhale about 15ish percent o2. So still plenty to keep someone alive.
But the lung stores “emergency air” in the form of the frc (functional reserve capacity). If you exhale normally, then try to force more out, there is more air in there. That is what oxygenated blood between breaths. So between the blood and the frc, there is actually several minutes of o2 in the body.
What we have found is that keeping the blood circulating is more important, and that just the movements from chest compressions is enough to get a bit of o2 back in the system. It’s not ideal, we would prefer to bag with 02 or a tube, but it will work short term.
We don’t breathe in and suck out all the o2, and breath out nothing but c02, I think that’s where the confusion comes in.
Source: pulmonologist/ intensive care doc whose job is to do cpr and run codes
Mouth to mouth doesn’t resuscitate someone, it’s used together with chest compressions to restart the heart beating on its own, and to help oxygenate the blood.
There are other gasses in the air. Also, your body doesn’t absorb 100% of the oxygen, and it doesn’t expel 100% CO2. What it expels is still better to have in someone’s lungs as opposed to them not breathing
The air you exhale contains almost as much oxygen as the air you inhale. There’s enough oxygen in the air you exhale for the person you’re resuscitating to be able to get enough oxygen to stay alive
it still has some oxygen, and it’ll get the lungs to reinflate (like a balloon)
does it work? eh.
is it better than literally anything else you can do without medical tools? yup.
Human lungs are really inefficient in their design. As we breathe out we have only used less than half of the available Ox in air. Birds with their much higher metabolism have air sacks and lungs and when they breathe the air flows _through_ the lungs in and out the air sacks. Rebreather diving equipment uses the residual Ox in exhalation to give longer diving times from same amount of Ox compared to trad. Scuba gear, of course the rebreather needs scrub the CO2.
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