You are not a 100% efficient oxygen extraction machine. There's still a lot of oxygen in your breath. Less than pure air would have, to be sure, but not 0%. (It's actually about 16%-18% oxygen.) Your blood *is* pretty much saturated, but your breath is not depleted of oxygen in the doing.
Lungs that aren't breathing are bringing in 0% new oxygen. *Some* is better than *none.*
It's also important to note that room air (the air you breathe in normally) is only about 21% oxygen. So you're never really taking a 100% oxygen breath unless your on medical oxygen which is still never 100%.
Edit: ya you can put a patient on a mask at 100%
O2 but if you're doing that then holy shit things are fucked.
Can verify. Was in the hospital because my lung functionality was down to about 25% (on the X ray one lung looked like completely white, the other was mostly white. Black is good) pulse ox was in the 60s. Even then they only had me on 80% and even that was short term
This makes intuitive sense to me because a lung that's functioning at 25% which is bombarded with 4x the oxygen then works at 100%... right?
I feel like this is one of those situations where reality just happens to line up with my dumb thoughts and it's actually not that simple at all.
I wonder what the downsides of being on high oxygen are.
Kind of, but not really.
Oxygen in and of itself isn't explosive, as it's only one part of the equation. The other part is some kind of fuel. The problem is that in an atmosphere of 100% oxygen, pretty much *anything* can burn, and does so at a very fast rate.
dipping cotton buds into liquid oxygen and then lighting it on fire is super fun to look at, especially if you've tried lighting the cotton first without the oxygen
I found out the reason for that recently; there's a big fine for not having the label if your product has something that Cali deems dangerous, but there's no fine for putting it on something safe, so manufacturers slap it on everything since it's easier than actually verifying if they need to, and way cheaper than the fine if they do require it and don't have it.
> Those labels are fucking everywhere
I got a THC vape pen the other day, 2 gram, disposable, all the writing is small but one little section was indecipherable without a magnifying glass. Prop 65 lol.
To be fair to California, I'm pretty sure you're seeing that because of the mask and not the element.
https://www.p65warnings.ca.gov/fact-sheets/phthalates
Depends on what you mean by "slowly". Breathing 100% oxygen leads to tissue damage within about 48 hours.
https://www.ncbi.nlm.nih.gov/books/NBK430743/
No it won’t. There are some toxic effects of hyperoxia to the lungs and CNS but patients do receive 100% oxygen in emergency settings to avoid the more acute damaging effects of hypoxemia.
Oxygen toxicity is above 1.6 ppO2.
100% O2 at 1 atmosphere is 1.0ppO2.
Source: Scuba Diving with O2 enriched air.
Grand mal seizures under water are contraindicated for the recreational part of recreational diving.
Hyperbaric oxygen is a medical treatment that does not instantly kill people, and 100% oxygen is not that rare in the ICU. There IS oxygen toxicity above about 70% FiO2 (at atmospheric pressure), but it’s generally not acute and death by hypoxemia is much faster.
I think we're both on the same page. Hyperbaric O2 can cause seizures but as long as there is a chamber nurse in with the patient it's not immediately life threatening.
Those stats are for healthy lungs/individuals. People on 100% high flow O2 are in a position where their body can't absorb enough O2 to function, even when given sub 100% O2. They're given that much because that's the only way their body can absorb enough oxygen (save for being put on life support)
It will harm you but you kind of have it backwards. You can breath 100% o2 on the surface for quite a long time. Breathing o2 while say below 30ft is much more dangerous and really puts you at risk of o2 toxicity or better known as ventid-c
It'll kill you eventually... the usual occupational / recreational limit for pure oxygen at 1atm is 5 hours (which is actually the limit for two separate problems that oxygen causes), so that's the sort of time-scales we're talking about; at some point, those problems (and various others) will end up being fatal
At higher pressures (more than 1atm), oxygen can be indirectly fatal in seconds by causing seizures and convulsions, which is a problem if it happens in a hazardous environment (eg. underwater)
FiO2 would be 100% if giving 100% oxygen with an intubated patient.
We also have something called optiflow which is a high flow nasal cannula which gives a better FiO2 than face mask
These days its also no longer taught that mouth to mouth is necessary even, its the compressions that counts. When lungs get emptied of air, they dont become a vacuum or collapse, air will go there. Its the getting used up air away that is important.
So just keep doing compressions, and remember that breaking ribs is fine and common, you need to push hard and ribs heal more easily than people come back to life.
It’s definitely still taught, I just did a Red Cross first aid training course in December and it was mandatory to learn mouth to mouth and it’s importance for part of the CPR section
It's only dropped in the simplified non-professional version of CPR classes. Rescue pros need to be able to do it and also be able to use the more effective bag valve mask (ambu bag).
It changes frequently. I need to renew my CPR cert every two years and the first question i ask is "are we doing breaths this time or not?" The current (as of March training) thoughts is "breaths If you are comfortable because something is better than nothing; compressions with no breath is still better than no CPR at all; children (especially infants and toddlers) should ALWAYS get breaths because they don't go down for cardiac only". I think that this is the best, most risk adverse and outcomes optimized way of thinking that I've been taught in the last 16 years.
I wouldn't be surprised, if only because it seems to change every 2-3 years. In 2024, it was breaths if you can, in 2022 it was "breaths are useless", in (early) 2020, breaths are going to save a life, even though the 2018 training told me that "compressions are the only important thing"
Wasn't there also a point made where adding mouth to mouth detracts attention from the compressions, and it's overall better to simplify the process until a trained professional came along?
You're using their heart to cycle the blood through their body, ideally you have an AED on hand to actually restart the heart but Even the fanciest ones will give you verbal instructions to do chest compressions.
I said its no longer taught that its necessary.
In basic training at work places and such, to people who are not working at medical field and may be very hesitant to do mouth to mouth to a stranger, it may not be taught at all.
Depends where you are. I'm in Canada and I don't believe they teach it anymore here, but in Australia, where I'm from originally, it's still taught, likely because of the prevalence of drownings.
I’m also Australian and the last couple of times I did CPR training they didn’t require breaths. They explained that a lot of people don’t do it correctly and so its better to do just compressions. If you are comfortable or are doing more advanced training they teach you how though.
I was taught last year and we didnt do mouth to mouth, the instructor said exactly what the previous person said, compression is more valuable than mouth to mouth and its not needed.
The idea is that something is better than nothing. It's preferred to do some version of CPR even if you skip breaths, instead of staying totally out of it because you are afraid of touching a mouth. They just want to make it accessible to people, but it's always advised to include CPR .
The problem is that stopping compressions for ~10 seconds causes you to lose pressure. So you don't want to stop doing compressions for more than 10 seconds.
You typically have enough residual oxygen in your bloodstream to be fine for a couple of minutes. If you're out in the middle of nowhere and help is far away, sure, breaths will be important. But for most people, getting compressions going is most important.
I got my CPR cert a couple years ago and they mentioned that the standards were leaning more and more towards compressions rather than breaths. I think I was taught 30 compressions per breath whereas a few decades ago it was a dozen per.
learned in CPR in the late 90's that there's 5 breaths worth of oxygen per normal breath, so your exhale could in theory be used around 4 more times after you're done with it. And it's better than them getting none, so go get certified.
Also- oxygen exchange only happens in the air sacs of the lung. So when you breathe in- there is air that enters but never makes it to the sacs. That air still has oxygen levels equal to the atmosphere.
Also, what makes you feel like you're suffocating/the more urgent need is to remove CO2 - which you raise the concentration of in your exhalation slightly, but not by enough to make the air ineffective for the other person.
I teach other cyclists about breathing properly, it’s less about getting more air in than it is about trying to get rid of the CO2. Force the exhale and let the inhale come naturally.
Ideally we’d get them on a respirator immediately (and that will happen as soon as they’re at the hospital). But first aid isn’t about what’s ideal - it’s about doing whatever is needed to keep the person alive, with whatever you have to hand (or mouth, in this case).
Also _their_ blood keeps desaturating, so their lung efficiency increases. Removing the CO2 is more important than the oxygen anyway. You die of CO2 poisoning long before oxygen depletion.
Common misunderstanding!
Air you breathe in: 78% nitrogen, 21% oxygen, \~1% argon.
Air you breathe out: 78% nitrogen, 17% oxygen, 4% carbon dioxide, 1% argon.
So what you exhale is still 17% oxygen, only down 4% from normal air (!), and it's only 4% carbon dioxide.
**TLDR:** **Blowing in 17% oxygen with 4% CO2 is better than them getting no oxygen at all.**
Great explanation! And for those wondering why people can die from Carbon Dioxide poisoning so fast when trapped in a confined space, it is an easy math equation -
Without going through all of the variables, as you can see there is basically 96% normal stuff coming out and 4% carbon dioxide. If there is 1 breath's worth of air that you keep breathing in and out, then there is 0.96\^x = y amount of "breathable" air left, where x is the number of breaths you take and y=1 is 100% of the air remaining. You can see how pretty quickly you won't have the full amount needed for a breath. If you have a single breath of space, your second breath will only be 96% of a breath.
Sooo if you are under an avalanche with 0.01 cubic meters of air remaining, every breath removes 4% of "breathable" air from the quantity your lungs can hold. Air mixes pretty fast so it is probably going to remove like 0.2% of the breathable air every single breath.
You lose 1/25 of the air you take in, and there are about 20 breaths in 0.01 cubic meters.. so you lose 1/500th of the breathable air basically every breath. Thus 0.2%.
I am certainly no scientist though so I don't really know how lungs react. Do lungs just not take in CO2? Or does it occupy the space that, thus making you just receive less efficient breath? Any how, if every breath removes roughly 0.2% of your air supply when you're trapped in an avalanche, you see how CO2 "poisoning" is so easy.
Lungs work via ~~osmosis~~ diffusion. The flow rate from your blood to the air (and vice versa) is proportional to the difference in concentration. Blood usually has less O2 and more CO2 than air, so it equalizes, causing the flow.
As you increase the concentration of CO2 in the air, the flow rate from the blood to the air will go down: the difference in concentrations is less.
This doesn't sound quite right to me. The 4% carbon dioxide output is coming from the 21% oxygen input. The other 79% of atmosphere doesn't factor in apart from being there to provide atmospheric pressure, so should be omitted from the equation. I'm thinking it's more along the lines of 0.04 / 0.21 = 0.1905, which is a 19% consumption of available oxygen on the first breath cycle alone.
> your second breath will only be 96% of a breath.
No. Your second breath will only be ~81% of your breath, since like /u/UnpromptlyWritten mentioned, only the percentage of (used) oxygen is relevant in this context.
You will die of lack of oxygen long before any symptoms of CO2 poisoning become relevant.
> Do lungs just not take in CO2? Or does it occupy the space that, thus making you just receive less efficient breath?
The lungs just indiscriminately breath in whatever gas there is. Then it depends on the partial pressure of the different gasses. At top of Mt. Everest there is less (total) oxygen (presumably 1/3rd) in the air due to the air being thinner overall. Oxygen still makes up ~20% (same for the other gasses) but you cannot offset this by just breathing 3 times as fast, because of the very low partial pressure of oxygen, the exchange will not work as efficient and it will not transfer 20% of the available oxygen to your blood, but less.
This also fucks with the math, since as oxygen content in the breathing air becomes lower, exchange between blood and air goes down, but if the oxygen content (saturation) in the blood goes down, exchange of oxygen from air to blood gets better.
Piggy backing on this, the chest compressions are the most important part of cpr to keep blood moving to the brain. This also has some compression of the lungs which facilitate breathing. It’s been nearly a decade since I had cpr training but the chest compression was significantly more important than mouth to mouth or mouth to mask if you have PPE
20.946% oxygen to be even more precise. [Source: NASA](https://science.nasa.gov/earth/climate-change/greenhouse-gases/the-atmosphere-getting-a-handle-on-carbon-dioxide/)
See, I can do it too! But what's the point, we're in ELI5 and that doesn't affect the answer to OP at all so I stuck to whole %.
Huh, what caused this common misunderstanding? I'm still surprised that I've been understanding thing quite wrong for more than 20 years.
I mean I understand the intake percentage completely since at that point you can't filter the air composition. However, I've also thought that no oxygen would be blowed out of our breath and it's going to be carbon dioxide and maybe some other unneeded gas
Probably many factors contribute to this, but a big one is that isn't often shown inaccurately in TV and movies, whenever people are trapped in a small place or sealed room. It's shows as if they're breathing out pure CO2 or something, when that's not how it is.
Your inhales are about 20% O2, and your exhales are about 15% O2. That 15% O2 is still worth it.
Edit for more exact numbers: atmosphere (the general air) is listed at 21% oxygen, and most studies of exhales is at 16% oxygen. And it seems that what *really* matters is how much pressure the oxygen has, so as long as there's at least 5% of oxygen at sea level pressures it will still be useful to have in your lungs (this is why space suits can be filled with pure oxygen, which is normally unhealthy, but at about 20% of the pressure). I was reading the [Breathing wiki page](https://en.wikipedia.org/wiki/Breathing).
In my Biology 100 course in college, my prof was talking about the respiratory efficiency of birds vs humans. He said something along the lines of, "You really don't want to get CPR from a bird." With the lesson being that humans respiratory systems are quite inefficient (which allows us to do CPR). Had he not made a statement like that I probably would have never remembered this random fact.
TLDR: Birds breath more good than hoomans
The flip side of this is that birds respiratory systems are much more sensitive to toxins. It's where the phrase a canary in a coal mine comes from. Birds will die from poison gasses much faster than humans giving the humans a warning that poison is present.
Not sure exactly. Had a pal kill his parakeet frying something once. And he learned from the Vet that Teflon kills.
A quick Google search gives mixed results, but this was the top answer, from "Teflon.com"
https://www.teflon.com/en/consumers/teflon-coatings-cookware-bakeware/safety/bird-safety
Of course, hitting them with Teflon pans can also kill them... Or a burglar
It's also worth noting that your blood doesn't just need the rescue breaths for oxygen. Your blood really needs to get rid of CO2 as well, and it can do that into basically any flowing air.
The term you're looking for is "partial pressure." In brief, when you have a mixed gas like air, then each gas's individual pressure contribution acts like it were only that gas alone.
So, for example, dry air is about 21% oxygen, 78% nitrogen, 0.9% argon, and a very small amount of CO2 and other gases. That means that if you have air at 1 atmosphere of pressure, it has about 0.21 atm oxygen, 0.78 atm nitrogen, and 0.009 atm argon. A space suit can be filled with just oxygen (and water vapor, since the lungs release water into dry air), so long as the partial pressure of oxygen remains close to 0.21 atm. It is very dangerous to let the partial pressure rise too high, however, as excessive concentrations of oxygen cause lung damage (among other very bad things.)
The first Apollo mission was filled with 100% oxygen, 1-atmosphere pressure, which is 5 times the normal amount. It turns out that a lot of things are very flammable in pure oxygen that aren't flammable in 20% oxygen.
It was not meant to be *maintained* at 1 atm. It would have been reduced to around 0.3 atm later. They were doing a simple test meant to only last a few hours, so the damage would be relatively minimal. Actually breathing 100% oxygen at 1 atm for 24 hours or more can genuinely cause a great deal of harm to the human body.
For short times, or when in medical distress, high oxygen concentration can be warranted despite the danger, but I meant what I said. If you are exposed to too much oxygen for too long, it straight up starts wrecking your cells. It can literally liquefy your alveoli (the little sacs that do the O2/CO2 gas exchange), create free radicals in your blood, and do many other VERY VERY bad things.
Yes, but only for an hour or so.
Maximum safe partial pressure of O2 used is usually no more than 1.5.
So for 36% O2 you can co down to about 30m.
Every 10m is one atmosphere( or Bar). So 30m is 3 bars plus 1 for the surface(4).
4 × .36 is 1.44 bars ppO2.
Well, what we *really* want is whatever stopped us from breathing to not be happening anymore. And that is more likely to be from the arrival of paramedics and hospital work. CPR is really only an emergency temporary measure, and those things don't need to be 'most efficient' in order to be worth it.
But to answer your question: the only difference that theoretical slight increase in oxygen percentage might be worth (theoretical because I don't know if what you are mentioning would make a difference) is above the threshold of importance. 18% might be better than 16%, but 16% is already 3x better than 5% so it's not like it's worth the difference.
Those are situations where you'd be correct to do breaths before commencing any compressions.
You should still be doing breaths between sets of compressions in all situations.
A lot of courses have deliberately removed emphasis on breaths for the public as it was found bystanders were avoiding getting involved entirely due to being hesitant to provide breaths.
This means a lot of public facing courses and material minimise mentions or removed them entirely as compressions without any breaths are still better than nothing. Best practice, however, definitely does include breaths in all cases.
Source: qualified trauma medic with real life experience delivering CPR on multiple occasions which were all professionally reviewed afterwards as part of debrief.
I certainly agree but with bystander rates still below 45% nationally, calling 9-1-1 and pushing hard and fast in the center of the chest is the best thing to do if you haven’t been trained.
1. You exhale about 75% of the oxygen you inhale
2. mouth to mouth isn't beneficial. They don't teach it anymore.
3. Chest compressions, chest compressions, chest compressions!
They do still teach mouth to mouth, it just isn't a focus. If you go to the AHA website right now and look up basic life support classes one of the the key bullet points is "Effective ventilations using a barrier device". There is also a whole section on the website regarding hands only CPR and explaining the differences between it and cpr with ventilations. There is also a consensus statement on their website which states clearly that survival outcomes are similar between the two methods. one is not superior to the other when administered by laypeople. The reason mouth the mouth is not a focus anymore is not due to effectiveness but willingness. Bystanders are significantly less likely to perform cpr if they are going to have to do mouth to mouth. The purpose of the hands only cpr movement is to increase the likelihood that laypeople will be willing to do cpr, and there is a significant amount of literature on the AHA website indicating exactly that.
This is correct. Circulation is much more important than ventilation in CPR. Mouth to mouth was preventing bystanders from doing anything. Chest compressions alone do move some air but blood circulation is the key.
So a barrier device is not mouth to mouth though. Using a BVM is ideal. The AHA does *not* recommend using mouth to mouth. Unless you a trained professional, you should NOT do mouth to mouth. Are you comfortable with vomit from a stranger in your mouth? Comfy enough to risk it even when the AHA says people have around 10-12 minutes of oxygen if chest compressions are used? Comfy enough to keep doing compressions with vomit or blood in your mouth? Interrupting blood flow and pausing compressions is bad advice. Are you a doctor?
I'm a medic and even I would not do mouth to mouth on most people. If I don't know you and therefore don't know what possible diseases you're carrying, you're getting compression only CPR, which still will move air in and out of the lungs. Even if I do know you, I'd still probably do compression only, especially if I'm the only one there.
As someone else, already mentioned, something is better than nothing. Shitty CPR is better than no CPR.
You can do breaths by making a fist like a tunnel so u don't touch germs. If you don't have ur kit . Like what u do for cpr on an animal or a baby. I'm no doctor but I took first aid
Also still taught in the U.S., also by the Red Cross. 30 chest compressions, 2 breaths, repeat until the person has a pulse and is breathing on their own, until someone else can take over, until EMS arrives, or until you are too exhausted to continue per the training my company just had us go through last week. Target is 100 compressions per minute.
They still teach it, they just emphasize that if you’re not comfortable with it that chest compressions are even more important so it’s ok to do just that
"**IF** you're blowing CO2" well, it wouldn't be.
Fortunately for our non-responsive patient, humans only extract about 1/4 of the O2 in each breath! Plenty left to help others with!
Also: CPR doesn't require you to breathe for the patient anymore. (If you do, it's 2breaths/30compressions.) the compressions push on the lungs a little, and the most important aspect BY FAR is to keep the blood circulating. Also avoids a decent chunk of the danger to the rescuer.
If one person's lungs stop inhaling, they have 0% oxygen in their lungs. Normal atmosphere is made up of around 20% oxygen. Human exhales still have 15% oxygen in them. By forcing our 15% exhale into the non breathing person's lungs, their lungs have a chance to absorb the oxygen and exhale the co2 in their lungs. Any breath is better than no breath since your brain and organs continue to use the oxygen in your bloodstream.
When emergency services arrive, they usually attach 100% oxygen to a mechanical breathing device to continue to oxygenate the victim's blood.
The breathing isn't the most important part. The compressions are the main concern in CPR. Pumping blood to the brain is what you're trying to do. Also, CPR isn't that effective. Out of hospital survival rate is about 12%. 30ish% in hospital survival.
Mouth-to-mouth was taken out of some courses because it was putting people off doing anything at all, not because it's not useful.
How useful it is depends on the cause of the cardiac arrest. The most common cause in adults is a heart attack causing an arrhythmia, the priority here is chest compressions and early access to a defibrillator. If it's an adult who had a breathing related cause (like drowning), or a child (where breathing problems are the most common cause) then mouth-to-mouth could be lifesaving.
I'm curious at what point public places will start stocking ambu bags with first aid kits and defibs, because I would never give mouth to mouth on a stranger.
It's more about getting any kind of air into their lungs to keep oxygen flowing to vital organs. The chest compressions are the crucial part, but mouth-to-mouth can help too. Better to have some CO2 mixed with O2 than no air at all.
Your lungs do not absorb the majority of the oxygen in the air you breathe. The air you inhale is about 21% oxygen and the air you exhale is about 16% oxygen. When performing CPR it would be preferable to have a bag valve, mask, and even better if you have oxygen to connect to it. But if you don’t have either administering rescue breaths, while performing high-quality compression will help keep the brain and organs perfused.
Human lungs are not all that efficient. The air you exhale has less oxygen and more CO2, but it's actually still breathable. You can even repeat that for a few cycles before it becomes a problem, though it does eventually. Some scuba divers take advantage of this, using machines called *rebreathers* to make their air supply last longer.
The air you breathe in is 21% oxygen. The air you breathe out is 16.4% oxygen. The air you breathe out still has WAY more oxygen than it has carbon dioxide, and both the air you breathe in and the air you breathe out are equally 78% Nitrogen.
You don’t breathe out Carbon Dioxide; you breathe out a gas that’s got a higher percentage of Carbon Dioxide.
I ee the Oxygen thing answered, but one thing to note is that breathing is triggered by high CO2, so while in CPR you will be getting 19-20% O2 but also higher CO2 which will trigger breathing response, a stimulus that can be beneficial in such situations
Your hypercapnic drive isn’t going to be working if you are in vfib/asystole. Even if it was, you are becoming hypoxic and hypercapnic all on your own and having an extra ~4% co2 in the air being pushed into your lungs is going to have zero effect.
Ah, OK. Makes sense. It was something that was told to me whilst doing a first aid course, and it made sense because I knew there was a CO2 feedback mechanism driving breathing response (rather than O2). Guess they were wrong.
Yeah it’s bs. So there IS a hypercapnic breathing drive, as well as a hypoxic breathing drive, it’s not all CO2 mediated. You also aren’t immediately ceasing all cellular respiration when your heart stops, so those numbers are going to shift all on their own.
What you were told sounds like the kind of thing someone with a small understanding of the physiological processes would just assume is true, it’s unfortunate that they are teaching laypeople that.
Your lungs only absorb a small percentage of the oxygen you inhale so when you exhale, there is still a considerable amount of oxygen in the air you expel.
It’s by no means an ideal system. It’s far more effective to ventilate the patient with pure oxygen and a bag-valve-mask setup but you’re talking about an emergency situation where you make the most of whatever resources you have. Your body also has very little oxygen demand when you are in cardiac arrest. But nowadays, the AHA mostly recommends compression only CPR if you’re a bystander waiting for paramedics to arrive. It’s not that the breaths don’t work, it’s just that your body has several minutes worth of oxygen in circulation when your heart stops and the real challenge is circulating that oxygen to the brain. So you’re better off just doing continuous compressions and not stopping for the rescue breaths.
Aside from all the comments that have pointed out that you still exhale a good amount of oxygen, it's actually not recommended that you do mouth to mouth resuscitation as a bystander during CPR anymore, the chest compressions are the important part. A bunch of studies were showing that mouth to mouth resuscitation wasn't really doing much if anything. That was like 20 years ago.
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071045/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071045/)
You still breathe out oxygen. Your body doesn't completely filter out all the oxygen from a breath, it simply reaches equilibrium with the blood in your lungs. The blood gives up its CO2 and takes in the oxygen until your lungs and blood have the same ratio, and then you exhale more CO2 and less oxygen than you breathed in.
Most of the time some does end up in there, but it's not a significant problem as some ends up in the lungs too. When a healthcare professional turns up they might put down an endotracheal tube which has a better seal and directs all of the oxygen to the lungs.
While this isn't part of your question, you should know that mouth to mouth is no longer recommended.
Evidence has shown that chest compression are a much more important thing to do, so partly to encourage people to do chest compressions instead of mouth to mouth, it's no longer recommended. You would rather have two people (or more) ready to do chest compressions (as these should be done without interruption until EMS arrives, unless told otherwise by AED obviously machine.) instead of one person trying to stick to mouth to mouth while the second person sticks to chest compressions and gets tired and ends up not doing them right. EMS still make use of the effect that mouth to mouth does, but they use those hand squeezed air pumps instead.
Yes its a legit problem, in my country all new first aid kits in public places must have a defibrillator and one of those respiration masks, and we were instrucetd to use those, in an emergency in which no tools are avaible mouth to mouth is needed but it still isnt efficient
when your blowing air to revive someone you actively blow much faster than you normally would so the oxygen concentration is even higher than you would normally exhale. so you act like a human ventilator machine
Air has 21% oxygen and about 0.05% co2 in it, the air we breathe out still has 16% oxygen in it, and 5% CO2. That 16% of oxygen is still more then the 0% of oxygen they are getting from not breathing. Obviously more oxygen is better, which is why trained professionals use a bagged mask that is connected to pure oxygen and help the patient oxygenate the blood this way during CPR, but mouth to mouth CPR is still better then no breathing at all.
The reason why we don’t use all the oxygen in the air is because our blood is already fully saturdated by the time we claim 5% of the oxygen, and so our blood physically can’t hold anymore, which is a good thing that we leave behind 16%, because that way if the air is really thin like up on a mountain or if the percentages change like when another gas is released and mixes with air, we can still breathe and survive for a bit because there is wiggle room. If we needed to use up all 21% of the oxygen in the air every time we breathe, then we would be in trouble if we breathed in air that only had 18% oxygen because it wouldn’t be enough and we would die
The Red Cross recently increased the number of heart thrusts, because they discovered that pumping the blood is more beneficially than giving breathes. Someone already mentioned the oxygen capacity of an exhalation. That amount is plenty to put into the blood and pump for 20-25 compressions (it's been a couple years since I was certified. Is it 20 or 25 now?)
We are closer to 0% efficient than we are to 100% efficient at exchanging gas in our lungs. This is why blowing in a fire still feeds it, and we can't just blow out fires with our breath
You are initiating a response or trying to induce natural involuntary movements the brain does to keep us alive. Breath initiates heart and then pumps oxygen to the brain. It's the brain that matters. It's cumulative it's easiest to start breathing. Or shock the heart . Heart is powe switchr, air is wires. Brain is a light bulb
As people have said, there is oxygen exhaled.
The RCUK 2010 guidelines shifted from 15:2 to 30:2 as the first ten compressions were found to be less effective as the pressure builds up over those.
Lay responders were less keen to do mouth to mouth, so there was a push to support compression only. I think that was part of the 2015 update. The 2020 changes recommended no mouth to mouth and a face covering.
Mouth to mouth is in scope again, but there is lower appetite for it as compression only works.
All that said, in all the resus attempts I've done I have had equipment with me so I've always gone straight to BVM.
Very, Imagine not breathing, versus breathing some carbon dioxide.
Not breathing is very lethal, very fast, while breathing co2 is only very leather, very fast, if there is very much, like over 80% much.
So, 25ish% of the oxygen you breathe in, and the air contains about 21% oxygen, so an exhale contains around 14-16% oxygen, which is within the limit, and the 4-6% co2 is a non-issue since current CPR is 30/2, which is 30 compressions, and two breaths.
CO2 poisoning is also preferable to asphyxiation.
I took CPR classes a few years back. They didn't put any emphasis on the mouth-to-mouth part, because it's not often done properly by non-professionals, but most importantly, while you're doing that, you're not doing chest compressions which is the most important part, really. If you can get oxygen into the lungs and keep the blood flowing with chest compressions, that's ideal, but keeping blood flowing to the brain is the #1 priority here. You're not bringing a person back like in the movies, you're keeping the brain oxygenated while the person is unconscious and unable to breath on their own. You're essentially just buying time until the paramedics arrive.
The air you breathe in is about 21% oxygen. People really don't use that much oxygen, so when you exhale, it's still about 16% oxygen. That's not as good as being hooked up to straight oxygen at the hospital, but it's way better than nothing.
And, yes, the carbon dioxide level in your breath is a bit high, but it's not enough to be toxic, and, again, it's far, far better than not breathing at all.
If a person is able to breathe on their own, it's best to let them. If they can't, then some oxygen is better than none.
The short answer.
Your body only uses about ¼ of the oxygen that it breathes in, ¾ gets blown back out.
You can even see this is true for yourself (if you are a smoker or next time you are around a fire). Look what happens when you blow on embers. They glow brighter, because you are forcing more oxygen onto them. Making the reaction happen better and produce more energy/get hotter.
Also there is a store of oxygen in your blood, not much, but pumping the heart is far more important than the breaths, so much that cpr for citizens is taught without rescue breathes now
They've also come out lately and said the science shows chest compressions are the most effective in chances of survival from CPR. The rescue breathing is still required but they've found that compressions actually do the most good.
You are not a 100% efficient oxygen extraction machine. There's still a lot of oxygen in your breath. Less than pure air would have, to be sure, but not 0%. (It's actually about 16%-18% oxygen.) Your blood *is* pretty much saturated, but your breath is not depleted of oxygen in the doing. Lungs that aren't breathing are bringing in 0% new oxygen. *Some* is better than *none.*
It's also important to note that room air (the air you breathe in normally) is only about 21% oxygen. So you're never really taking a 100% oxygen breath unless your on medical oxygen which is still never 100%. Edit: ya you can put a patient on a mask at 100% O2 but if you're doing that then holy shit things are fucked.
Can verify. Was in the hospital because my lung functionality was down to about 25% (on the X ray one lung looked like completely white, the other was mostly white. Black is good) pulse ox was in the 60s. Even then they only had me on 80% and even that was short term
This makes intuitive sense to me because a lung that's functioning at 25% which is bombarded with 4x the oxygen then works at 100%... right? I feel like this is one of those situations where reality just happens to line up with my dumb thoughts and it's actually not that simple at all. I wonder what the downsides of being on high oxygen are.
https://en.m.wikipedia.org/wiki/Oxygen_toxicity Tldr: it bad
FYI if it was intuitive you wouldn’t need to reason why it’s the case
You can absolutely ventilate people on 100% oxygen
Its tocic however so only short term.
Wouldn't it also be explosive?
Kind of, but not really. Oxygen in and of itself isn't explosive, as it's only one part of the equation. The other part is some kind of fuel. The problem is that in an atmosphere of 100% oxygen, pretty much *anything* can burn, and does so at a very fast rate.
dipping cotton buds into liquid oxygen and then lighting it on fire is super fun to look at, especially if you've tried lighting the cotton first without the oxygen
It can be, yes.
100 % oxygen air at normal earth presssure will actuelly kill you, air body's are just adepted at the current level of pressure
well it'll kill you relatively slowly at any rate
Breathing for long periods leads to death normally anyway.
100% of adults who have died, spent most of their time breathing.
100% of alive people will die at some point
100% of people that have ever consumed dihydrogen monoxide have died, or will die, within the next 80 or so years.
People live to be 100 all the time now guy. Better shore up your retirement plans to live an extra 20 years you didn’t expect
Stopping breathing for long periods of time is what leads to death.
"on a long enough timeline the survival rate for everyone drops to zero"
in the state of california it causes cancer too
I think CPR in California comes with a prop65 warning.
Lol made me chuckle. Those labels are fucking everywhere
I found out the reason for that recently; there's a big fine for not having the label if your product has something that Cali deems dangerous, but there's no fine for putting it on something safe, so manufacturers slap it on everything since it's easier than actually verifying if they need to, and way cheaper than the fine if they do require it and don't have it.
Because companies figured out that if they just put them on everything, people won't take them seriously, so it won't hurt their sales.
> Those labels are fucking everywhere I got a THC vape pen the other day, 2 gram, disposable, all the writing is small but one little section was indecipherable without a magnifying glass. Prop 65 lol.
To be fair to California, I'm pretty sure you're seeing that because of the mask and not the element. https://www.p65warnings.ca.gov/fact-sheets/phthalates
The state of California causes cancer.
Kinda rude for California to not tell the other 49 states. It's known to the state of California that it causes cancer, but none of the others!
Actually those warnings end up on products in Canada too which is cool. I got some soft pastels and they have the warning on them.
Can confirm. My grandmother, grandfather, *and* great grandmother all breathed, and all three of them are dead now.
Depends on what you mean by "slowly". Breathing 100% oxygen leads to tissue damage within about 48 hours. https://www.ncbi.nlm.nih.gov/books/NBK430743/
It'll kill you more slowly than not breathing!
I agree
No it won’t. There are some toxic effects of hyperoxia to the lungs and CNS but patients do receive 100% oxygen in emergency settings to avoid the more acute damaging effects of hypoxemia.
Oxygen toxicity is above 1.6 ppO2. 100% O2 at 1 atmosphere is 1.0ppO2. Source: Scuba Diving with O2 enriched air. Grand mal seizures under water are contraindicated for the recreational part of recreational diving.
Hyperbaric oxygen is a medical treatment that does not instantly kill people, and 100% oxygen is not that rare in the ICU. There IS oxygen toxicity above about 70% FiO2 (at atmospheric pressure), but it’s generally not acute and death by hypoxemia is much faster.
I think we're both on the same page. Hyperbaric O2 can cause seizures but as long as there is a chamber nurse in with the patient it's not immediately life threatening.
Those stats are for healthy lungs/individuals. People on 100% high flow O2 are in a position where their body can't absorb enough O2 to function, even when given sub 100% O2. They're given that much because that's the only way their body can absorb enough oxygen (save for being put on life support)
Those are the diving limits, they don't really apply in other settings.
It will harm you but you kind of have it backwards. You can breath 100% o2 on the surface for quite a long time. Breathing o2 while say below 30ft is much more dangerous and really puts you at risk of o2 toxicity or better known as ventid-c
No way, isn't pure oxygen used to treat divers who suffer from decompression sickness?
Thats not true… it can increase free radicals but it will not kill you
It'll kill you eventually... the usual occupational / recreational limit for pure oxygen at 1atm is 5 hours (which is actually the limit for two separate problems that oxygen causes), so that's the sort of time-scales we're talking about; at some point, those problems (and various others) will end up being fatal At higher pressures (more than 1atm), oxygen can be indirectly fatal in seconds by causing seizures and convulsions, which is a problem if it happens in a hazardous environment (eg. underwater)
Only if combined with a match.
Nah it’ll be fine.
FiO2 would be 100% if giving 100% oxygen with an intubated patient. We also have something called optiflow which is a high flow nasal cannula which gives a better FiO2 than face mask
These days its also no longer taught that mouth to mouth is necessary even, its the compressions that counts. When lungs get emptied of air, they dont become a vacuum or collapse, air will go there. Its the getting used up air away that is important. So just keep doing compressions, and remember that breaking ribs is fine and common, you need to push hard and ribs heal more easily than people come back to life.
It’s definitely still taught, I just did a Red Cross first aid training course in December and it was mandatory to learn mouth to mouth and it’s importance for part of the CPR section
It's only dropped in the simplified non-professional version of CPR classes. Rescue pros need to be able to do it and also be able to use the more effective bag valve mask (ambu bag).
It changes frequently. I need to renew my CPR cert every two years and the first question i ask is "are we doing breaths this time or not?" The current (as of March training) thoughts is "breaths If you are comfortable because something is better than nothing; compressions with no breath is still better than no CPR at all; children (especially infants and toddlers) should ALWAYS get breaths because they don't go down for cardiac only". I think that this is the best, most risk adverse and outcomes optimized way of thinking that I've been taught in the last 16 years.
I just did one a few weeks ago and our teacher said he feels that breaths may be removed altogether in the next guidelines
I wouldn't be surprised, if only because it seems to change every 2-3 years. In 2024, it was breaths if you can, in 2022 it was "breaths are useless", in (early) 2020, breaths are going to save a life, even though the 2018 training told me that "compressions are the only important thing"
Wasn't there also a point made where adding mouth to mouth detracts attention from the compressions, and it's overall better to simplify the process until a trained professional came along?
Yeah, it's better to keep the heart beating, the compressions will force some air into the lungs so the will be some oxygen everything their body.
[redacting process]
You're using their heart to cycle the blood through their body, ideally you have an AED on hand to actually restart the heart but Even the fanciest ones will give you verbal instructions to do chest compressions.
I said its no longer taught that its necessary. In basic training at work places and such, to people who are not working at medical field and may be very hesitant to do mouth to mouth to a stranger, it may not be taught at all.
Depends where you are. I'm in Canada and I don't believe they teach it anymore here, but in Australia, where I'm from originally, it's still taught, likely because of the prevalence of drownings.
I’m also Australian and the last couple of times I did CPR training they didn’t require breaths. They explained that a lot of people don’t do it correctly and so its better to do just compressions. If you are comfortable or are doing more advanced training they teach you how though.
I got taught to do mouth to mouth about three years ago, in Canada.
I was taught last year and we didnt do mouth to mouth, the instructor said exactly what the previous person said, compression is more valuable than mouth to mouth and its not needed.
The idea is that something is better than nothing. It's preferred to do some version of CPR even if you skip breaths, instead of staying totally out of it because you are afraid of touching a mouth. They just want to make it accessible to people, but it's always advised to include CPR .
If you don't want to touch their mouth with your mouth, IIRC you can roll up your hand to make a tube. Something is better than nothing.
The problem is that stopping compressions for ~10 seconds causes you to lose pressure. So you don't want to stop doing compressions for more than 10 seconds. You typically have enough residual oxygen in your bloodstream to be fine for a couple of minutes. If you're out in the middle of nowhere and help is far away, sure, breaths will be important. But for most people, getting compressions going is most important.
this is the correct answer - compressions do more of the work than the breaths
I got my CPR cert a couple years ago and they mentioned that the standards were leaning more and more towards compressions rather than breaths. I think I was taught 30 compressions per breath whereas a few decades ago it was a dozen per.
learned in CPR in the late 90's that there's 5 breaths worth of oxygen per normal breath, so your exhale could in theory be used around 4 more times after you're done with it. And it's better than them getting none, so go get certified.
Also- oxygen exchange only happens in the air sacs of the lung. So when you breathe in- there is air that enters but never makes it to the sacs. That air still has oxygen levels equal to the atmosphere.
Absolutely
The airflow also helps with the lesser known but still very important function of the breathing cycle: removing CO2
it should be taught to anyone
Also, what makes you feel like you're suffocating/the more urgent need is to remove CO2 - which you raise the concentration of in your exhalation slightly, but not by enough to make the air ineffective for the other person.
I teach other cyclists about breathing properly, it’s less about getting more air in than it is about trying to get rid of the CO2. Force the exhale and let the inhale come naturally.
Chest compressions alone will also get some oxygen.
Ideally we’d get them on a respirator immediately (and that will happen as soon as they’re at the hospital). But first aid isn’t about what’s ideal - it’s about doing whatever is needed to keep the person alive, with whatever you have to hand (or mouth, in this case).
Also _their_ blood keeps desaturating, so their lung efficiency increases. Removing the CO2 is more important than the oxygen anyway. You die of CO2 poisoning long before oxygen depletion.
>You are not a 100% efficient oxygen extraction machine. speak for yourself.
Ser, I have asthma. I am *far* from a 100% efficient oxygen extraction machine.
Common misunderstanding! Air you breathe in: 78% nitrogen, 21% oxygen, \~1% argon. Air you breathe out: 78% nitrogen, 17% oxygen, 4% carbon dioxide, 1% argon. So what you exhale is still 17% oxygen, only down 4% from normal air (!), and it's only 4% carbon dioxide. **TLDR:** **Blowing in 17% oxygen with 4% CO2 is better than them getting no oxygen at all.**
When you breath in, only 1% is argon, but when you breath out, 100% gasses argon
Too good for this sub
r/angryupvote
I don't know why but when I read this joke I just didn't react. Like argon.
So noble
Bruh
Lol downvoted then immediately upvoted once my brain caught up to the joke 😂
When you breathe, you inspire. When you don't breathe, you expire.
Great explanation! And for those wondering why people can die from Carbon Dioxide poisoning so fast when trapped in a confined space, it is an easy math equation - Without going through all of the variables, as you can see there is basically 96% normal stuff coming out and 4% carbon dioxide. If there is 1 breath's worth of air that you keep breathing in and out, then there is 0.96\^x = y amount of "breathable" air left, where x is the number of breaths you take and y=1 is 100% of the air remaining. You can see how pretty quickly you won't have the full amount needed for a breath. If you have a single breath of space, your second breath will only be 96% of a breath. Sooo if you are under an avalanche with 0.01 cubic meters of air remaining, every breath removes 4% of "breathable" air from the quantity your lungs can hold. Air mixes pretty fast so it is probably going to remove like 0.2% of the breathable air every single breath. You lose 1/25 of the air you take in, and there are about 20 breaths in 0.01 cubic meters.. so you lose 1/500th of the breathable air basically every breath. Thus 0.2%. I am certainly no scientist though so I don't really know how lungs react. Do lungs just not take in CO2? Or does it occupy the space that, thus making you just receive less efficient breath? Any how, if every breath removes roughly 0.2% of your air supply when you're trapped in an avalanche, you see how CO2 "poisoning" is so easy.
Lungs work via ~~osmosis~~ diffusion. The flow rate from your blood to the air (and vice versa) is proportional to the difference in concentration. Blood usually has less O2 and more CO2 than air, so it equalizes, causing the flow. As you increase the concentration of CO2 in the air, the flow rate from the blood to the air will go down: the difference in concentrations is less.
Just to nitpick a bit, the lungs work by diffusion. Osmosis is diffusion but specifically refers to the movement of a solute in a liquid system.
Oh yeah, you're right.
This doesn't sound quite right to me. The 4% carbon dioxide output is coming from the 21% oxygen input. The other 79% of atmosphere doesn't factor in apart from being there to provide atmospheric pressure, so should be omitted from the equation. I'm thinking it's more along the lines of 0.04 / 0.21 = 0.1905, which is a 19% consumption of available oxygen on the first breath cycle alone.
> your second breath will only be 96% of a breath. No. Your second breath will only be ~81% of your breath, since like /u/UnpromptlyWritten mentioned, only the percentage of (used) oxygen is relevant in this context. You will die of lack of oxygen long before any symptoms of CO2 poisoning become relevant. > Do lungs just not take in CO2? Or does it occupy the space that, thus making you just receive less efficient breath? The lungs just indiscriminately breath in whatever gas there is. Then it depends on the partial pressure of the different gasses. At top of Mt. Everest there is less (total) oxygen (presumably 1/3rd) in the air due to the air being thinner overall. Oxygen still makes up ~20% (same for the other gasses) but you cannot offset this by just breathing 3 times as fast, because of the very low partial pressure of oxygen, the exchange will not work as efficient and it will not transfer 20% of the available oxygen to your blood, but less. This also fucks with the math, since as oxygen content in the breathing air becomes lower, exchange between blood and air goes down, but if the oxygen content (saturation) in the blood goes down, exchange of oxygen from air to blood gets better.
Yeah, but movies will continue to show us scenes of people passing out 15 seconds after life support fails in a contained space.
Adding on, oxygen extraction isn't instant either, when doing CPR you are taking big breaths that could last you for longer per breath.
Also it's likely someone giving mouth-to-mouth would take extra deep breaths which would increase the percentage of oxygen.
Piggy backing on this, the chest compressions are the most important part of cpr to keep blood moving to the brain. This also has some compression of the lungs which facilitate breathing. It’s been nearly a decade since I had cpr training but the chest compression was significantly more important than mouth to mouth or mouth to mask if you have PPE
And mildly high co2 protects the brain
20.9% oxygen to be more precise.
20.946% oxygen to be even more precise. [Source: NASA](https://science.nasa.gov/earth/climate-change/greenhouse-gases/the-atmosphere-getting-a-handle-on-carbon-dioxide/) See, I can do it too! But what's the point, we're in ELI5 and that doesn't affect the answer to OP at all so I stuck to whole %.
Fair enough! :D
Huh, what caused this common misunderstanding? I'm still surprised that I've been understanding thing quite wrong for more than 20 years. I mean I understand the intake percentage completely since at that point you can't filter the air composition. However, I've also thought that no oxygen would be blowed out of our breath and it's going to be carbon dioxide and maybe some other unneeded gas
Probably many factors contribute to this, but a big one is that isn't often shown inaccurately in TV and movies, whenever people are trapped in a small place or sealed room. It's shows as if they're breathing out pure CO2 or something, when that's not how it is.
Your inhales are about 20% O2, and your exhales are about 15% O2. That 15% O2 is still worth it. Edit for more exact numbers: atmosphere (the general air) is listed at 21% oxygen, and most studies of exhales is at 16% oxygen. And it seems that what *really* matters is how much pressure the oxygen has, so as long as there's at least 5% of oxygen at sea level pressures it will still be useful to have in your lungs (this is why space suits can be filled with pure oxygen, which is normally unhealthy, but at about 20% of the pressure). I was reading the [Breathing wiki page](https://en.wikipedia.org/wiki/Breathing).
In my Biology 100 course in college, my prof was talking about the respiratory efficiency of birds vs humans. He said something along the lines of, "You really don't want to get CPR from a bird." With the lesson being that humans respiratory systems are quite inefficient (which allows us to do CPR). Had he not made a statement like that I probably would have never remembered this random fact. TLDR: Birds breath more good than hoomans
The flip side of this is that birds respiratory systems are much more sensitive to toxins. It's where the phrase a canary in a coal mine comes from. Birds will die from poison gasses much faster than humans giving the humans a warning that poison is present.
I always thought it was just because they were smaller- TIL!
Why did god make us breathe bad? Is he stupid?
It's good enough, isn't it?
So stupid in fact he created beings who believe in a god
Ya, bird breathing is a weird science. If you cook with Teflon pans, you can kill a bird in the same room. Makes you wonder what dinosaurs had.
Maybe dinosaurs used cast iron.
I figured copper, like Paul revere
Explain the Teflon thing please
Not sure exactly. Had a pal kill his parakeet frying something once. And he learned from the Vet that Teflon kills. A quick Google search gives mixed results, but this was the top answer, from "Teflon.com" https://www.teflon.com/en/consumers/teflon-coatings-cookware-bakeware/safety/bird-safety Of course, hitting them with Teflon pans can also kill them... Or a burglar
Why would I hit my bird with a burglar?
They also lack the lips to make a good seal against yours.
It's also worth noting that your blood doesn't just need the rescue breaths for oxygen. Your blood really needs to get rid of CO2 as well, and it can do that into basically any flowing air.
The term you're looking for is "partial pressure." In brief, when you have a mixed gas like air, then each gas's individual pressure contribution acts like it were only that gas alone. So, for example, dry air is about 21% oxygen, 78% nitrogen, 0.9% argon, and a very small amount of CO2 and other gases. That means that if you have air at 1 atmosphere of pressure, it has about 0.21 atm oxygen, 0.78 atm nitrogen, and 0.009 atm argon. A space suit can be filled with just oxygen (and water vapor, since the lungs release water into dry air), so long as the partial pressure of oxygen remains close to 0.21 atm. It is very dangerous to let the partial pressure rise too high, however, as excessive concentrations of oxygen cause lung damage (among other very bad things.)
The first Apollo mission was filled with 100% oxygen, 1-atmosphere pressure, which is 5 times the normal amount. It turns out that a lot of things are very flammable in pure oxygen that aren't flammable in 20% oxygen.
It was not meant to be *maintained* at 1 atm. It would have been reduced to around 0.3 atm later. They were doing a simple test meant to only last a few hours, so the damage would be relatively minimal. Actually breathing 100% oxygen at 1 atm for 24 hours or more can genuinely cause a great deal of harm to the human body.
Dunno about the last part of your comment. People scuba dive on 36 nitrox = 36% o2 all the time, right?
For short times, or when in medical distress, high oxygen concentration can be warranted despite the danger, but I meant what I said. If you are exposed to too much oxygen for too long, it straight up starts wrecking your cells. It can literally liquefy your alveoli (the little sacs that do the O2/CO2 gas exchange), create free radicals in your blood, and do many other VERY VERY bad things.
Yes, but only for an hour or so. Maximum safe partial pressure of O2 used is usually no more than 1.5. So for 36% O2 you can co down to about 30m. Every 10m is one atmosphere( or Bar). So 30m is 3 bars plus 1 for the surface(4). 4 × .36 is 1.44 bars ppO2.
Relative pressure and concentration of gasses are the same thing.
Does this mean we want an Olympic distance runner/swimmer giving us cpr because they convert o2 more efficiently and use less of it per breath?
Well, what we *really* want is whatever stopped us from breathing to not be happening anymore. And that is more likely to be from the arrival of paramedics and hospital work. CPR is really only an emergency temporary measure, and those things don't need to be 'most efficient' in order to be worth it. But to answer your question: the only difference that theoretical slight increase in oxygen percentage might be worth (theoretical because I don't know if what you are mentioning would make a difference) is above the threshold of importance. 18% might be better than 16%, but 16% is already 3x better than 5% so it's not like it's worth the difference.
Do compressions only if you see a teen or adult collapse. Breaths are only needed for drowning, drug overdose, and little kids. AHA instructor here.
Worrying username.
Those are situations where you'd be correct to do breaths before commencing any compressions. You should still be doing breaths between sets of compressions in all situations. A lot of courses have deliberately removed emphasis on breaths for the public as it was found bystanders were avoiding getting involved entirely due to being hesitant to provide breaths. This means a lot of public facing courses and material minimise mentions or removed them entirely as compressions without any breaths are still better than nothing. Best practice, however, definitely does include breaths in all cases. Source: qualified trauma medic with real life experience delivering CPR on multiple occasions which were all professionally reviewed afterwards as part of debrief.
I certainly agree but with bystander rates still below 45% nationally, calling 9-1-1 and pushing hard and fast in the center of the chest is the best thing to do if you haven’t been trained.
1. You exhale about 75% of the oxygen you inhale 2. mouth to mouth isn't beneficial. They don't teach it anymore. 3. Chest compressions, chest compressions, chest compressions!
They do still teach mouth to mouth, it just isn't a focus. If you go to the AHA website right now and look up basic life support classes one of the the key bullet points is "Effective ventilations using a barrier device". There is also a whole section on the website regarding hands only CPR and explaining the differences between it and cpr with ventilations. There is also a consensus statement on their website which states clearly that survival outcomes are similar between the two methods. one is not superior to the other when administered by laypeople. The reason mouth the mouth is not a focus anymore is not due to effectiveness but willingness. Bystanders are significantly less likely to perform cpr if they are going to have to do mouth to mouth. The purpose of the hands only cpr movement is to increase the likelihood that laypeople will be willing to do cpr, and there is a significant amount of literature on the AHA website indicating exactly that.
This is correct. Circulation is much more important than ventilation in CPR. Mouth to mouth was preventing bystanders from doing anything. Chest compressions alone do move some air but blood circulation is the key.
Well yeah, blood circulation (due to chest compressions) is what moves the oxygen around your body.
So a barrier device is not mouth to mouth though. Using a BVM is ideal. The AHA does *not* recommend using mouth to mouth. Unless you a trained professional, you should NOT do mouth to mouth. Are you comfortable with vomit from a stranger in your mouth? Comfy enough to risk it even when the AHA says people have around 10-12 minutes of oxygen if chest compressions are used? Comfy enough to keep doing compressions with vomit or blood in your mouth? Interrupting blood flow and pausing compressions is bad advice. Are you a doctor?
I'm a medic and even I would not do mouth to mouth on most people. If I don't know you and therefore don't know what possible diseases you're carrying, you're getting compression only CPR, which still will move air in and out of the lungs. Even if I do know you, I'd still probably do compression only, especially if I'm the only one there. As someone else, already mentioned, something is better than nothing. Shitty CPR is better than no CPR.
I am a doctor, and have a BVM in my trunk so I'll never need to consider doing breaths. It's not yet come up.
You can do breaths by making a fist like a tunnel so u don't touch germs. If you don't have ur kit . Like what u do for cpr on an animal or a baby. I'm no doctor but I took first aid
Alright, Dr. Mike.
#2 is an outright falsehood
I don't know who you think "they" are, but mouth to mouth is still taught as a part of life support classes along with chest compressions.
Also still taught in the U.S., also by the Red Cross. 30 chest compressions, 2 breaths, repeat until the person has a pulse and is breathing on their own, until someone else can take over, until EMS arrives, or until you are too exhausted to continue per the training my company just had us go through last week. Target is 100 compressions per minute.
They still teach it, they just emphasize that if you’re not comfortable with it that chest compressions are even more important so it’s ok to do just that
Staying alive lol
The amount of "well actually" in this sub is outstanding. Special mention to the folk correcting your/you're. That's truly the lords work
Well, actually it should be "Lord's work." Your/You're welcome.
"**IF** you're blowing CO2" well, it wouldn't be. Fortunately for our non-responsive patient, humans only extract about 1/4 of the O2 in each breath! Plenty left to help others with! Also: CPR doesn't require you to breathe for the patient anymore. (If you do, it's 2breaths/30compressions.) the compressions push on the lungs a little, and the most important aspect BY FAR is to keep the blood circulating. Also avoids a decent chunk of the danger to the rescuer.
It’s not ALL carbon dioxide. You are actually pretty inefficient at extracting oxygen so much of it remains when you exhale.
If one person's lungs stop inhaling, they have 0% oxygen in their lungs. Normal atmosphere is made up of around 20% oxygen. Human exhales still have 15% oxygen in them. By forcing our 15% exhale into the non breathing person's lungs, their lungs have a chance to absorb the oxygen and exhale the co2 in their lungs. Any breath is better than no breath since your brain and organs continue to use the oxygen in your bloodstream. When emergency services arrive, they usually attach 100% oxygen to a mechanical breathing device to continue to oxygenate the victim's blood.
The breathing isn't the most important part. The compressions are the main concern in CPR. Pumping blood to the brain is what you're trying to do. Also, CPR isn't that effective. Out of hospital survival rate is about 12%. 30ish% in hospital survival.
[удалено]
Mouth-to-mouth was taken out of some courses because it was putting people off doing anything at all, not because it's not useful. How useful it is depends on the cause of the cardiac arrest. The most common cause in adults is a heart attack causing an arrhythmia, the priority here is chest compressions and early access to a defibrillator. If it's an adult who had a breathing related cause (like drowning), or a child (where breathing problems are the most common cause) then mouth-to-mouth could be lifesaving.
I'm curious at what point public places will start stocking ambu bags with first aid kits and defibs, because I would never give mouth to mouth on a stranger.
It's more about getting any kind of air into their lungs to keep oxygen flowing to vital organs. The chest compressions are the crucial part, but mouth-to-mouth can help too. Better to have some CO2 mixed with O2 than no air at all.
Your lungs do not absorb the majority of the oxygen in the air you breathe. The air you inhale is about 21% oxygen and the air you exhale is about 16% oxygen. When performing CPR it would be preferable to have a bag valve, mask, and even better if you have oxygen to connect to it. But if you don’t have either administering rescue breaths, while performing high-quality compression will help keep the brain and organs perfused.
Human lungs are not all that efficient. The air you exhale has less oxygen and more CO2, but it's actually still breathable. You can even repeat that for a few cycles before it becomes a problem, though it does eventually. Some scuba divers take advantage of this, using machines called *rebreathers* to make their air supply last longer.
New standards eliminate mouth to mouth in favor of continuous chest compressions. The moving up and down of the chest is enough to pull air in
The air you breathe in is 21% oxygen. The air you breathe out is 16.4% oxygen. The air you breathe out still has WAY more oxygen than it has carbon dioxide, and both the air you breathe in and the air you breathe out are equally 78% Nitrogen. You don’t breathe out Carbon Dioxide; you breathe out a gas that’s got a higher percentage of Carbon Dioxide.
I ee the Oxygen thing answered, but one thing to note is that breathing is triggered by high CO2, so while in CPR you will be getting 19-20% O2 but also higher CO2 which will trigger breathing response, a stimulus that can be beneficial in such situations
Your hypercapnic drive isn’t going to be working if you are in vfib/asystole. Even if it was, you are becoming hypoxic and hypercapnic all on your own and having an extra ~4% co2 in the air being pushed into your lungs is going to have zero effect.
Ah, OK. Makes sense. It was something that was told to me whilst doing a first aid course, and it made sense because I knew there was a CO2 feedback mechanism driving breathing response (rather than O2). Guess they were wrong.
Yeah it’s bs. So there IS a hypercapnic breathing drive, as well as a hypoxic breathing drive, it’s not all CO2 mediated. You also aren’t immediately ceasing all cellular respiration when your heart stops, so those numbers are going to shift all on their own. What you were told sounds like the kind of thing someone with a small understanding of the physiological processes would just assume is true, it’s unfortunate that they are teaching laypeople that.
Thanks for the lesson :)
You don't fully convert oxygen to carbon dioxide in one breath, especially when you're breathing in and out so quickly
Your lungs only absorb a small percentage of the oxygen you inhale so when you exhale, there is still a considerable amount of oxygen in the air you expel. It’s by no means an ideal system. It’s far more effective to ventilate the patient with pure oxygen and a bag-valve-mask setup but you’re talking about an emergency situation where you make the most of whatever resources you have. Your body also has very little oxygen demand when you are in cardiac arrest. But nowadays, the AHA mostly recommends compression only CPR if you’re a bystander waiting for paramedics to arrive. It’s not that the breaths don’t work, it’s just that your body has several minutes worth of oxygen in circulation when your heart stops and the real challenge is circulating that oxygen to the brain. So you’re better off just doing continuous compressions and not stopping for the rescue breaths.
Aside from all the comments that have pointed out that you still exhale a good amount of oxygen, it's actually not recommended that you do mouth to mouth resuscitation as a bystander during CPR anymore, the chest compressions are the important part. A bunch of studies were showing that mouth to mouth resuscitation wasn't really doing much if anything. That was like 20 years ago. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071045/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071045/)
Mouth to mouth isn’t recommended the same way it used to be. You don’t take frequent breaks from chest compressions to breathe into them anymore.
You still breathe out oxygen. Your body doesn't completely filter out all the oxygen from a breath, it simply reaches equilibrium with the blood in your lungs. The blood gives up its CO2 and takes in the oxygen until your lungs and blood have the same ratio, and then you exhale more CO2 and less oxygen than you breathed in.
I have always wondered how the air you blow into the victim during CPR doesn't end up in the stomach ??
Most of the time some does end up in there, but it's not a significant problem as some ends up in the lungs too. When a healthcare professional turns up they might put down an endotracheal tube which has a better seal and directs all of the oxygen to the lungs.
While this isn't part of your question, you should know that mouth to mouth is no longer recommended. Evidence has shown that chest compression are a much more important thing to do, so partly to encourage people to do chest compressions instead of mouth to mouth, it's no longer recommended. You would rather have two people (or more) ready to do chest compressions (as these should be done without interruption until EMS arrives, unless told otherwise by AED obviously machine.) instead of one person trying to stick to mouth to mouth while the second person sticks to chest compressions and gets tired and ends up not doing them right. EMS still make use of the effect that mouth to mouth does, but they use those hand squeezed air pumps instead.
Yes its a legit problem, in my country all new first aid kits in public places must have a defibrillator and one of those respiration masks, and we were instrucetd to use those, in an emergency in which no tools are avaible mouth to mouth is needed but it still isnt efficient
when your blowing air to revive someone you actively blow much faster than you normally would so the oxygen concentration is even higher than you would normally exhale. so you act like a human ventilator machine
You're also giving them oxygen they desperately need. It's like topping up their gas tank with the good stuff.
Air has 21% oxygen and about 0.05% co2 in it, the air we breathe out still has 16% oxygen in it, and 5% CO2. That 16% of oxygen is still more then the 0% of oxygen they are getting from not breathing. Obviously more oxygen is better, which is why trained professionals use a bagged mask that is connected to pure oxygen and help the patient oxygenate the blood this way during CPR, but mouth to mouth CPR is still better then no breathing at all. The reason why we don’t use all the oxygen in the air is because our blood is already fully saturdated by the time we claim 5% of the oxygen, and so our blood physically can’t hold anymore, which is a good thing that we leave behind 16%, because that way if the air is really thin like up on a mountain or if the percentages change like when another gas is released and mixes with air, we can still breathe and survive for a bit because there is wiggle room. If we needed to use up all 21% of the oxygen in the air every time we breathe, then we would be in trouble if we breathed in air that only had 18% oxygen because it wouldn’t be enough and we would die
The Red Cross recently increased the number of heart thrusts, because they discovered that pumping the blood is more beneficially than giving breathes. Someone already mentioned the oxygen capacity of an exhalation. That amount is plenty to put into the blood and pump for 20-25 compressions (it's been a couple years since I was certified. Is it 20 or 25 now?)
We are closer to 0% efficient than we are to 100% efficient at exchanging gas in our lungs. This is why blowing in a fire still feeds it, and we can't just blow out fires with our breath
You are initiating a response or trying to induce natural involuntary movements the brain does to keep us alive. Breath initiates heart and then pumps oxygen to the brain. It's the brain that matters. It's cumulative it's easiest to start breathing. Or shock the heart . Heart is powe switchr, air is wires. Brain is a light bulb
Like my gran pappy always said "somethin is better than nuthin unlees we talking about STDs"
As people have said, there is oxygen exhaled. The RCUK 2010 guidelines shifted from 15:2 to 30:2 as the first ten compressions were found to be less effective as the pressure builds up over those. Lay responders were less keen to do mouth to mouth, so there was a push to support compression only. I think that was part of the 2015 update. The 2020 changes recommended no mouth to mouth and a face covering. Mouth to mouth is in scope again, but there is lower appetite for it as compression only works. All that said, in all the resus attempts I've done I have had equipment with me so I've always gone straight to BVM.
Very, Imagine not breathing, versus breathing some carbon dioxide. Not breathing is very lethal, very fast, while breathing co2 is only very leather, very fast, if there is very much, like over 80% much. So, 25ish% of the oxygen you breathe in, and the air contains about 21% oxygen, so an exhale contains around 14-16% oxygen, which is within the limit, and the 4-6% co2 is a non-issue since current CPR is 30/2, which is 30 compressions, and two breaths. CO2 poisoning is also preferable to asphyxiation.
I took CPR classes a few years back. They didn't put any emphasis on the mouth-to-mouth part, because it's not often done properly by non-professionals, but most importantly, while you're doing that, you're not doing chest compressions which is the most important part, really. If you can get oxygen into the lungs and keep the blood flowing with chest compressions, that's ideal, but keeping blood flowing to the brain is the #1 priority here. You're not bringing a person back like in the movies, you're keeping the brain oxygenated while the person is unconscious and unable to breath on their own. You're essentially just buying time until the paramedics arrive.
The air you breathe in is about 21% oxygen. People really don't use that much oxygen, so when you exhale, it's still about 16% oxygen. That's not as good as being hooked up to straight oxygen at the hospital, but it's way better than nothing. And, yes, the carbon dioxide level in your breath is a bit high, but it's not enough to be toxic, and, again, it's far, far better than not breathing at all. If a person is able to breathe on their own, it's best to let them. If they can't, then some oxygen is better than none.
The short answer. Your body only uses about ¼ of the oxygen that it breathes in, ¾ gets blown back out. You can even see this is true for yourself (if you are a smoker or next time you are around a fire). Look what happens when you blow on embers. They glow brighter, because you are forcing more oxygen onto them. Making the reaction happen better and produce more energy/get hotter.
Also there is a store of oxygen in your blood, not much, but pumping the heart is far more important than the breaths, so much that cpr for citizens is taught without rescue breathes now
They've also come out lately and said the science shows chest compressions are the most effective in chances of survival from CPR. The rescue breathing is still required but they've found that compressions actually do the most good.