If we breathe out carbon dioxide why does CPR work?
In: Biology
CPR is when you go into cardiac arrest. At this point, the circulatory system is already failing because the heart isn’t pumping blood. CPR has two stages – 30 chest compressions and two breaths. If you’re at the stage where your heart has stopped, the chances are slim of CPR restarting the heartbeat without additional support from an AED.
Our lungs exchange O2 with CO2, but not all of it.
Going in, the air is: 78% Nitrogen, 21% oxygen and .04% CO2.
Coming out its: still 78% Nitrogen, but now ~15% oxygen and 5% CO2. So there’s still oxygen in it.
If you’re performing assisted breathing on someone its because they can’t breath on their own. So the 15% O2 you’re _forcing_ into their lungs is better than whatever little they’re getting on their own account.
Because your body doesn’t consume all of the oxygen in the air. So when you exhale into someone else’s lungs there is still oxygen present.
It’s very rare for rescuers to perform mouth to mouth these days. Most models of arrest management in developed countries with robust emergency services systems have moved towards hands only CPR. We’ll still deliver oxygen, but it’s from a bottle through a face mask or a breathing tube. The initial bystander rescuers should be focusing on quality compressions and clearing the airway rather than performing mouth to mouth. Yes, we breathe out enough oxygen for the patient to use as others have stated. In this day and age, it’s generally not required as compressions are far more important.
Source: Am a paramedic.
Because we don’t breathe out pure carbon dioxide. We breathe out sir with just a little bit less oxygen than it had before. Don’t ask why we’re so inefficient like that, we just are.
Even if you don’t breathe for them though, pumping their heart is still useful because there is still a fair bit of oxygen in their blood.
Normal air is about 21% oxygen, 0.1% carbon dioxide, and a bunch of other stuff. The air we breathe out has about 4% carbon dioxide and 16% oxygen. We do not consume all the oxygen or breathe out pure carbon dioxide. That does cut down on the amount of oxygen a CPR recipient receives a bit, but forcing someone to breathe 16% oxygen is better than them not breathing in any oxygen.
Just don’t sing ‘Another one bites the dust’ while performing it on anyone. People don’t like that one. ‘Stayin’ Alive’ is a better song to do it to.
A real ELI5 explanation:
You push on the chest fast, about 100 times every minute, to keep the blood moving through the body because the heart isn’t working. Even if you can’t give any extra oxygen, CPR still helps because any oxygen is better than none. If the brain doesn’t get oxygen it dies piece by piece.
“Source”: respiratory therapist who has participated in a lot of in-hospital CPR efforts
FYI the most important part of CPR are the compressions to keep blood flowing through your body, not the rescue breaths. If you have to choose either or, choose compressions every time.
Giving 2 breaths per ~30 compressions is optimal, but not if the person was choking or has an open mouth wound.
Some people have explained it, but I want to throw in there that this is why you often teach people to use very quick, even shallow breaths when giving CPR. You want to give your own body as little time to process the oxygen as possible before you bellow it into their lungs. You get your oxygen in between breaths for them.
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