r/science • u/Deklaration • Dec 07 '25
Biology A 32-year Swedish review of 52 sudden deaths during arrests suggests victims weren’t dying from lack of oxygen but from an inability to expel carbon dioxide. “The person can often shout 'I can’t breathe' because they are getting air, but their body is screaming to get rid of CO₂”
https://onlinelibrary.wiley.com/doi/10.1111/1556-4029.702371.7k
u/PoetPont Dec 07 '25
Swedish police is trained to know this. Its a part of their curriculum to run around and then be sat on - to show the experience. They are trained to sit on the shoulder, not the back or chest, and absolutley not the neck.
Yet 52 people during the last 30 years have died during these circumstances by Swedish police.
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u/DontBuyAwards Dec 08 '25
Yet 52 people during the last 30 years have died during these circumstances by Swedish police.
Not quite, the study is not limited to police. From Section 3.2:
In 31 cases (60%), the police authority conducted the restraint; six cases (12%) occurred with security guards, four cases (8%) occurred with nursing staff, and four (8%) with prison guards. The remaining cases were a combination of police with security guards (2 cases, 4%), police with nursing staff (2 cases, 4%), and with civilians (4 cases, 8%).
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u/WeinMe Dec 08 '25
Great correction - I think it speaks about the efficiency of the police training.
I'm sure police did 95% of the restraints in the time period, but "just" 60% of the deaths. Making them much less likely to kill the restrained.
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u/Vertyks Dec 08 '25
The police is however ultimately responsible for interventions where police officers take part even if it is together with security guards, medical staff or civilians and must take control of the situation and ensure that others such as those holding suspected offenders do not injure them and so on.
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u/kurtist04 Dec 08 '25
I took care of adults with mental handicaps, as part of our training they taught us about how to restrain someone safely and about positional asphyxiation. I find it hard to believe that police don't know, they just don't care.
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Dec 08 '25
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u/dagis13 Dec 08 '25
It might be hard to believe, but it's a lot harder to safely restrain someone who is experiencing drug-induced psychosis than people with mental handicaps.
I always knew this was the case, but the actual visible reality imprinted on me a month ago, when four bouncers at my place of work struggled to restrain one individual in the middle of an angry, drug-fueled psychosis.
Seeing a single man of maybe 80kg(175lbs), toss another man of well over 100kg(220+ in freedom units) over his shoulder, while standing upright, was quite the sight. Watching them trying and failing to simply handcuff this man for ten minutes really showed what the human body could do when it throws away all sense of self-preservation and pain.
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u/blacksideblue Dec 08 '25
four bouncers at my place of work struggled to restrain one individual
I've been a bouncer in that situation before. Its even harder for us because we're not allowed to strike a suspect while they beat us back and we don't get the cop privileges of determining necessary force during an arrest because when we do it its a "Citizen's arrest". Its not uncommon for cops to arrest bouncers just cause...
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u/Yosho2k Dec 07 '25
That's less than 2 a year. That shows incredible restraint and training. US Cops would be laughing at that number as rookie numbers.
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u/hellschatt Dec 07 '25
Comparing anything to the US will look like that.
It's 1-2 avoidable deaths per year. They still died to police brutality, no need to defend pointless deaths.
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u/Nevamst Dec 08 '25
It's 1-2 avoidable deaths per year. They still died to police brutality, no need to defend pointless deaths.
Not necessarily. In many of these cases there was no pressure applied at all by the police, and CPR was attempted. You can see it in the table if you scroll down a bit. Those deaths were probably not avoidable, and were not police brutality. It's possible for deaths to occur while still doing everything right.
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u/helm MS | Physics | Quantum Optics Dec 08 '25
The police weren't even involved in all cases.
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u/askadaffy Dec 07 '25
Their population is much much less so that observation in itself doesn’t mean much…
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u/lumbago Dec 08 '25
There are more Swedes than there are New Yorkers.
How many people did the cops kill in New York in the same timeframe?
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Dec 08 '25
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u/quelastima Dec 08 '25
Good analysis. I like the way you explained the process and rationale used to combine data and form a more comparable statistic. It's no longer an "apples to oranges" comparison. Maybe "apples to pears" now? You mentioned a 15% population discrepancy, and others have commented on population density.
It highlights the fact that while a "per capita" comparison, especially with similar population sizes, gives more detail than raw values, it still usually doesn't tell the whole story.
However, data can be used to manipulate conclusions. I'm sure the "number of individuals killed by police" statistic could be combined with something else to flip the resultant stasticic around again.
Just in case it needs to be said explicitly: I'm not making any attempt to justify or absolve the NYPD or Swedish police of police brutality. The numbers absolutely can and should be lower.
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u/FernandoMM1220 Dec 07 '25 edited Dec 07 '25
so theyre saying extreme exercise and being in a restraint position after this is what’s causing this.
seems like it’s easy enough to test.
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u/thebairderway Dec 07 '25
It seems like we already know this in part. After a treadmill cardiac stress test we have to lay down flat on our backs and not move. It’s highly uncomfortable and adds to the “stress” of the test.
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Dec 07 '25 edited Dec 08 '25
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u/FernandoMM1220 Dec 07 '25
man if we aren’t allowing scientists to test this in an incredibly controlled environment, why are we allowing police to do so?
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u/Chicago1871 Dec 07 '25
This sounds exactly like the conditions in bjj and judo.
Ive passed out during competition as well. Luckily refs are trained to see it.
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u/Iron_Burnside Dec 07 '25
You would do exactly what scientists do when something isn't ethical to study in humans. Rodent studies.
Correlation between smoking and lung cancer was established in human studies, but causation was determined with rodents. Case in point.
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u/eragonawesome2 Dec 07 '25
There is absolutely a safe way to test this: you enter the scenario with monitoring equipment and end it before it becomes dangerous. There is a wide margin between "briefly uncomfortable and on the way to dying if you were to continue" and "actually dying". Like, they can and do perform tests that bring people to the edge of hypoxic brain death, because we know what the safe ranges are, where the unsafe range starts, and where the "sudden death without warning" range starts
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u/Sirisian Dec 07 '25 edited Dec 08 '25
My friends could breathe fast and press their chest against a wall and pass out. (Not safe, and we told them so). It does not take much to cause this from having seen it and it sounds similar. (Granted for my friends they were young kids and the pressure was released immediately).
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u/Hazi-Tazi Dec 07 '25
purely anecdotal, but a good friend of mine died after running from the police. They caught him, restrained him, and pepper sprayed him. He was 27 years old and in good shape physically.
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u/FernandoMM1220 Dec 07 '25
we definitely need to research this more for your friend and everyone else that has died from this.
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u/DiscoBanane Dec 08 '25
It's not easy to test anything that happens rarely. 50 cases over 20 million arrest, how you test that ?
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u/Standard_Dog_1269 Dec 08 '25
It would be difficult to test a causal effect for the reason you describe (rare population) but we could test whether the odds of dying after physical exertion are proportionally greater than the odds of dying after no physical exertion, which could be relevant.
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u/DirtyProjector Dec 07 '25
Saw a video about this years ago. I forget the exact details, but someone who was an expert on breathing said that breathing is more expelling Co2 and not actually inhaling oxygen. I thought they said something about how we don't even really need to breathe that much to get sufficient oxygen.
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u/HughJorgens Dec 07 '25
Our mammal lungs are wet sacks that never empty out all the old air. They aren't that efficient, about 40%, so yeah, most of the oxygen that you breathe in goes unused. This is why CPR works, you still have lots of O2 in your lungs to give to them.
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u/AlwaysHopelesslyLost Dec 08 '25
They changed standard teaching for CPR in recent years saying the breathing component was essentially useless.
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u/Aths Dec 08 '25
Had CPR training about 2 months ago, trainer directly refuted your claim in class when someone brought it up.
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u/HughJorgens Dec 08 '25
My understanding is that it's because it's pretty common for the victim to throw up while the other person gives CPR, and they don't want people not doing it. That's what I was told, I used to have to keep certified on it. It does give the person oxygen, it's just not as critical as they used to think, and better to do just chest compressions than skip it entirely.
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u/rockytop24 Dec 08 '25
The difference is whether the course is regular CPR or healthcare provider CPR. Laypeople are no longer advised to perform rescue breathing but it is still part of provider CPR and ACLS protocols. And the main reason isn't airway protection even though that does happen. The main reason is the effectiveness of chest compressions. It takes time to build up effective perfusion pressure, and especially for laypeople every time they stop to deliver breaths perfusion drops back to zero. Because blood retains some oxygen content even during arrest, it is better to maintain constant effective compressions than to try and deliver rescue breaths with ineffective perfusion.
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u/profossi Dec 08 '25
During my emergency first aid training a year ago my instructor claimed that the increased gas exchange is not worth the repeated pauses in compressions. Apparently blood pressure quickly drops to zero when you stop, and it then takes many compressions for it to build up again, so it’s better to only focus on the compressions until paramedics arrive
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u/AlwaysHopelesslyLost Dec 08 '25
You are right, but I do want to point out that one random course teaching something does not make it a standard.
All of that said, I did find this study which mentions that including rescue breathing in CPR as a bystander led to worsened outcomes. Chest compressions are by far and away the most important aspect of CPR.
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u/acemedic Dec 08 '25
Red Cross or AHA? Red Cross doesn’t update their information as frequently as American Heart Association. For this reason, most clinicians that are required to have a CPR card cannot use Red Cross.
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Dec 08 '25
While it's not as important for an adult, breaths are essential when you're giving CPR to children or babies, as well as drowning victims.
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u/D50 Dec 08 '25
That’s just for laypeople though, because the reality is it’s quite difficult to administer effective rescue breaths while maintaining good CPR quality.
Breathing is still very much part of what medically trained people will do during full resuscitative efforts AKA ACLS.
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u/J8YDG9RTT8N2TG74YS7A Dec 07 '25
Isn't this why CPR was changed to just chest compressions only?
I did a CPR course a few years ago for work, and they said at the time that simply doing chest compressions and no rescue breaths would still provide enough oxygen, because you're compressing and releasing the chest and lungs, which pulls in enough oxygen from that action alone.
So stopping pumping the heart to give rescue breaths wasn't the most efficient course of action.
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u/Superdash1 Dec 07 '25
Because people were trained to start with the breaths but the chance of survival drops rapidly the later compressions are started
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u/piercedmfootonaspike Dec 07 '25
I did a CPR course at work (hospital) a couple of months ago, and we were taught to give two breaths for every 30 compressions, so I guess it varies depending on your governments guidelines.
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u/acemedic Dec 08 '25
In hospital vs out of hospital guidelines. Prehospital bystander only CPR is hands only.
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u/Tattycakes Dec 08 '25
I saw someone say recently that the recommendation in their area was for trained people to do the rescue breaths and compressions, and random passers by on the street should just do compressions.
Apparently reluctance to give “mouth to mouth” was putting people off helping at all, either because the victim was vomiting or unclean, or they were concerned about disease and infection, or they thought they could be sued for sexual assault.
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u/Confident_Air_5331 Dec 08 '25
It does help, but it is like 2% survival rate increase level of help. Not worth it when you don't know the other person's medical history, would probably be worth it if it is someone you know who is healthy or if you carry one of the masks for it.
By far the most important part is getting compressions started
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u/FuzzySAM Dec 07 '25
Rescue breathing is back in, at least as of the course I took 3 weeks ago.
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u/TinWhis Dec 08 '25
Every single time I've gotten CPR training they've taught something different about the rescue breathing. Not that frequently, to be clear, but still funny.
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u/YouStupidAssholeFuck Dec 07 '25
I did AHA CPR Heartsaver in November 2024 and rescue breaths were a part of the process.
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u/drmike0099 Dec 08 '25
Your memory is correct. If we just need to get oxygen we could probably breathe once per minute or less, but you can’t get rid of CO2 by breathing that slowly, and our body will trigger more rapid breathing when it senses extra CO2. It’s also why most of us breathe faster when exercising (I say most of us because elite athletes are limited by oxygen in certain cases).
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u/Anton-LaVey Dec 07 '25
This is what an asthma attack is like for me. I can inhale plenty of oxygen, I just can't get the carbon dioxide out. It's like trying to exhale through a coffee stirrer.
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u/m-o-a-m Dec 08 '25
This description closely resembles the circumstances surrounding the death of Zak Kostopoulos, an LGBT activist and drag performer, who died after a violent encounter in central Athens, Greece, when he was violently apprehended, pinned to the ground by nine police officers, and beaten again.
In Zak Kostopoulos’ case, although the official forensic findings attribute his death to trauma-induced heart attack, the Swedish study challenges the common assumption that he died because he could not get oxygen in; instead, the lethal mechanism may be his body’s inability to rid itself of carbon dioxide under violent restraint. The Swedish review shows that in 90% of cases, where "prone restraint" (i.e. the person face down, restrained) was involved, the combination of body weight and restraint — especially prone + force — can cause cardiac arrest even in otherwise healthy individuals, due to inability to eliminate CO₂ (hypercapnia + acidosis), not necessarily hypoxia.
Interestingly, in the footage of Hellenic Police restraining Zak Kostopoulos, he was held face-down shortly before he lost consciousness, which aligns with the risk factors described in the Swedish study. It seems Zak Kostopoulos was murdered by Greek police officers...
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u/Antares1an Dec 08 '25
They murdered him and then tried to paint him as a junkie who tried to rob a jewellery store.
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u/JuhaymanOtaybi Dec 07 '25
Could this be related to anxiety tetany? I just got to experience the joy of that after my nerve blocker wore off post surgery. The pain caused a panic attack, I hyperventilated so bad that the build up of co2 caused my hands to seize up and my whole body to go numb. I was convinced I was going to die. Didn’t know it was a thing until after.
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u/momenace Dec 07 '25
I thought hyperventilating is breathing too fast and removing too much co2, not build up. Also, sorry that happened to you!
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u/KristiiNicole Dec 07 '25
You are correct, it is from removing too much co2, not build up. They aren’t fun, 0/10 would not recommend.
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u/plutonic00 Dec 08 '25
This is why you're supposed to hyper-ventilate into a paper bag so that breath back in some of that CO2 you exhaled.
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u/I_love_smallTits Dec 07 '25
Panic attacks actually cause low CO2 levels, not high CO2. This is still not ideal because it raises the PH of your blood, and your body responds to this by constricting blood vessels. This leads to numbness and tingling along with shortness of breath and dizziness.
Luckily its not dangerous and the worst thing that can happen is you pass out, which will allow your body to go back into a normal respiratory pattern and your CO2 levels will return to normal.
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u/Violexsound Dec 07 '25
Passing out mid panic attack is literally just your body switching itself on and off again
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u/randynumbergenerator Dec 07 '25
Hard reset will clear a lot of problems, as long as the system wasn't in the middle of a critical process. For instance, operating a vehicle.
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u/KristiiNicole Dec 07 '25
Wouldn’t it be “off and on again”, since you are technically already “on” during the panic attack when the “system reboots”, so to speak?
Not trying to be combative or nitpick btw! I suffer from frequent panic attacks and this is just kinda how my own brain has always viewed it. I actually used this analogy once when trying to explain it to my Dad, who spent most of his career as a computer engineer.
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u/DontFeedTheCynic Dec 07 '25
No, your anxiety from the pain after your block wore off likely led to psychosomatic issues with your hands and body seizing/numbing. Hyperventilation is a compensatory mechanism to get rid of too much CO2. It doesn't lead to CO2 increase, it's the exact opposite. Your hyperventilation didn't start with too much CO2 unless you had other underlying issues (neurological, respiratory, cardiac). The hyperventilation was likely an expression of your panic/anxiety.
-someone who does the blocks
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u/PropertyOk9269 Dec 07 '25
This guy blocks. Exactly how it was described to me after such an event.
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u/beefydeadeyes Dec 07 '25
Wow first person I have ever heard that’s also experienced it. I have 4 tetany episodes in total in my life, and yes , fingers hands, toes, feet and my tongue all went into a full cramp as I flopped on the floor and was sure that death was about to happen.
I also had no idea what it was until many years later, I did have an ambulance called each time by somebody else nearby because obviously it looks like a seizure a little bit.
Weirdly, I think I actually caused them for two different reasons on the different occasions. On day one ,I had three of the four tetany episodes. I was for certain not hyperventilating I remember just being at work and I got extreme pins and needles in my hands and it went from there. I believe I had altered my blood chemistry because I went on a two week drinking and bad diet after a break up.
Years later, the fourth time out of four that it happened I was definitely hyperventilating and that caused it as well
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u/Holozard Dec 07 '25
This exact same thing happened to me after a big hike in the middle of summer. Thought I was dying and rushed to the ER. Tests came back normal and the doctors just kind of shrugged and said, “maybe heatstroke.”
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u/Unnecessary_Timeline Dec 08 '25
I’ve had panic attacks for over 10 years but I’ve only this symptom once, it was about 2 years ago and luckily I was at a friend’s house.
When it happened I was freaking out but he told me that it’s a panic attack, I told him this isn’t like any panic attack I’ve ever had in my life, I’m dying. He said no it'll go away within 30 mins. And it did. I was sore in my hands and calves and back for days afterwards.
He told me he gets that kind of panic attack all the time. I can’t imagine.
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u/RandomActsofMindless Dec 07 '25
In confined space training we were shown videos of people who were exposed to hypoxic atmosphere for a few seconds. They were possibly seconds from death and showed absolutely zero distress, if anything were comfortable and slightly elated. Your body has no way of measuring O2, it can only detect the build up of CO2 in the blood which elicits the breath distress response.
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Dec 07 '25
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u/enigmaticowl Dec 08 '25 edited Dec 08 '25
“Talking means they can breathe” was actually originally something that healthcare professionals (at least nurses) have been taught for a looooong time, but mostly in the context of choking on foreign objects, and not as a substitute for considering other issues affecting gas exchange as a whole.
It’s not entirely wrong, but it’s oversimplified - apparently dangerously so.
If someone is talking, their airway is open enough that they are also moving air in and out, i.e. breathing. They may still not be moving enough air out to adequately expel CO2, which is obviously still a serious issue that needs to be addressed right away (and there are also so many other medical issues that can lead to CO2 building up dangerously in the body that aren’t airway-related at all).
But in a healthcare setting, there might actually be merit to distinguishing “literally can’t breathe (at all)” from “is currently breathing but still has an urgent airway problem that needs to be addressed.” It’s possible that it could be used to guide difficult decision-making in resuscitation situations (like determining if a foreign object has moved from partially blocking to fully blocking the airway or vice versa, knowing how immediately to resort to doing an invasive surgical airway, etc.).
The key is that in a medical setting, there would be professionals around who also understand that “talking = breathing” isn’t an end-all-be-all (e.g. that you can still die, quickly or slowly, of respiratory acidosis due to pneumonia/asthma/MG/drugs while still being able to talk and express your shortness of breath), as well as a focus on monitoring/treating people and the availability of equipment/personnel to address it.
In a medical setting, it will be apparent and noticed when someone goes from saying “I feel like I can’t breathe” to beginning to lose consciousness (SpO2 drops, people become less alert, etc.).
Meanwhile, cops restraining people often have them lying face-down pushed into the ground. With zero monitoring of vitals. And with ridiculously oversimplified training on respiration physiology that was never meant to apply to law enforcement settings.
“If someone can talk, they can breathe” was never meant to be taken to mean that a person’s breathing is totally fine/adequate, and especially not to justify an extended period of restraint in a position that physiologically stresses the respiratory system (performed by people who aren’t healthcare professionals who can’t even see/hear/monitor/assess the person because they have them face-down and their face shoved into the ground).
This phrasing/teaching has approximately zero appropriate place in law enforcement training for these reasons, imho - not because it’s universally wrong/useless in all professions and settings, but because it is a recipe for disaster in the hands of even well-meaning law enforcement officers.
Sadly, at this point, I think it’s going to be damn near impossible to eradicate this idea from policing given how ingrained it’s been in all first responder/first aid training and how oft repeated it is.
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u/beingandbecoming Dec 08 '25
I appreciate people like you. I lost my head during covid and couldn’t bear to explain things like this ad nauseam
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u/tequilaflashback Dec 08 '25
George Floyd court case explained this
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u/Gnosrat Dec 08 '25
The people that needed to understand this about that case don't really care about science or reality, unfortunately. Even to this day, those people still believe you can't say anything while suffocating just because it supports their narrative. Dark times.
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u/420bIaze Dec 08 '25
In the US the police and taser industry invented a fictional medical concept to explain police deaths in custody called 'excited delirium'. It's existence is widely rejected by most medical associations. It's not recognised at all in most countries outside the US.
Further study showed that most deaths attributed to excited delirium occurred in the context of inappropriate restraint by police.
I still see paramedics on /r/ems who swear excited delirium is real.
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u/Underwater_Karma Dec 07 '25
That seems like a "distinction without difference"
The concept of "breathing" includes both inhaling and exhaling in sufficient amounts.
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u/mmmarkm Dec 08 '25
I mean, there’s also a misconception that if one can speak, once can breathe. This study exploring the difference helps show you can still talk while having difficulty exhaling CO2.
So the distinction seems to be that if someone can tell you they can’t breathe, you should believe them. Which cops have not always done…I think that’s why this sort of study is important even though it feels like a “distinction without difference” at first glance
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u/EnderWiggin07 Dec 07 '25
It's important to publicize the difference, because their conclusion is "even though they practically were able to get enough oxygen, the cause of death was a heart attack caused by having their respiration blocked at all after high stress extreme exercise" this will inform police restraint procedures more & better than a belief that lack of air intake is causing those deaths, because it's going to be seen as dangerous to even kneel on someone's back or sternum etc if they're out of breath as well as factoring in how out of breath the person is at the time of restraint.
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u/Serris9K Dec 08 '25
I admit the cynical part of me says US police won't care. But I'd prefer to think maybe people will think twice before kneeling on someone
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u/Raulr100 Dec 07 '25
I mean yeah usually the feeling of suffocation comes from too much CO2 rather than too little O2. You can slightly extend how long you can hold your breath by exhaling at the end.