If we breathe out carbon dioxide why does CPR work?
In: Biology
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.
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.
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.
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.
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.
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.
Aside from the comments below, I would add that a fair percent of the air that you breath in, never makes it to the alveoli in the lungs to be exchanged for CO2. All the air that just makes it into your upper airway, trachea and bronchi is still 21% oxygen. So the first several seconds of exhaled air is still oxygen saturated. (But as already noted…mouth to mouth is never done anymore…occasionally mouth to one way mask)
Educational fact for those that don’t know CPR: on tv, they always show the person doing cpr blowing pretty long. You’re actually suppose to do it for just like a second or two- or about an normal breath.
And if you’re not breaking ribs, you’re not pressing hard enough. Gotta go down on the chest a couple of inches.
One thing everyone is missing is that in cases of asphyxiation your lungs rely on the presence of CO2 to help trigger a breath. If your lungs are full of N2 or He for example you simply stop breathing and die.
CPR helps with circulation of blood and will help revive. In a lot of cases chest compressions alone will help save the life of heart attack victims.
CPR is more about circulating blood than it is about air going in and out. Don’t get me wrong, air going in and out is important, but air can go in and out and do nothing if blood isn’t going around and around.
It takes a lot of both, with medications intertwined to bring someone back. CPR is just maintaining the body’s most basic system.
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