If we breathe out carbon dioxide why does CPR work?



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.

The main reason isn’t the breathing, it is because you are pumping their heart for them, when it has stopped or isn’t working properly.

The cells in your brain use the oxygen in the blood cells already beside them almost immediately they are in contact. By pumping the persons heart, you move those empty blood cells away and push new blood cells that still have oxygen in them into place. The oxygen already in your blood before you stopped breathing is enough for a few minutes.

After that, the air from your lungs still has enough oxygen in it, that it is able to give enough oxygen to the empty cells to keep you going even longer. When you breathe out, you breath out 3/4 of all the oxygen you breathe in, and only take out 1/4.

AEMT here:
Your oxygen is saturated with up to 100% oxygen at most points. (Edit: unless you have underlying health issues) When your heart stops, it stops pumping. The oxygenated blood is still in your arteries, so by pumping the heart, it moves that blood to the tissues. The tissues then exchange CO2 with your blood, and the cycle continues.

You only have a small percentage of CO2 in your body, relatively speaking. This builds up over time, along with lactic acid(which is a byproduct of anaerobic metabolism, AKA: cells not having O2) and causes acidosis in your blood. You then need more advanced medications such as Sodium Bicarbonate, which helps buffer that acidosis.

The number one goal of CPR is to maintain blood perfusion, which means the proper flow of blood through all tissues. If someone’s cardiovascular system fails to pump blood properly to the brain, the blood will just sit in the vessels and become quickly deoxygenated. Unconsciousness will follow very quickly, probably within 10-20 seconds or less if fresh oxygenated blood does not pass through those critically important blood vessels in the brain. It is important to note the brain has a very high demand for oxygen and energy compared to the rest of the body.

Chest compressions work to promote blood perfusion through manual pumping of the heart. It’s not great, it won’t last forever, but it will keep blood flowing through the brain, even if it isn’t fully oxygenated. The oxygen hungry brain needs something, anything to keep it alive, and the idea is that as you do chest compressions you are also pushing air in and out of the lungs, allowing for some air exchange.

Without rapid advanced life support and transport to medical facilities, the chance of living isn’t too great, something like 10%. This is case-dependent, because there are different scenarios that cause cardiovascular impairment. Maybe there is fibrillation where the heart beats erratically, maybe a myocardial infarction where blood flow is somewhat restricted or even completely cut off to the heart and the tissue starts to die.

What CPR does is buy time by allowing the flow of precious oxygenated blood to the brain and other sensitive tissues, so that advanced lifesaving measures may be taken. Defibrillation is also extremely important, and if an AED is nearby it is paramount that someone who knows what they’re doing hooks it up to the person.

The steps to save someone’s life who is likely suffering a cardiac emergency is: Check the pulse and breathing, have someone CALL 911! Perform chest compressions at a rate of at least 60 per minute, perhaps with a rescue breath every 30 seconds if you are comfortable. If there is an AED nearby, get it and use it.

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.

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.

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

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.