As a Neuroscientist and breathwork facilitator, do you think there is any harm in intentional apnea (e.g. free diving, static holds, ect)?

At what point does cell damage (not necessarily death), kick in? As someone involved in these sports, I operate under the assumption that any damage would kick in after loss of consciousness. For example, if I hold my breath, even for 4 or 5 minutes but dont pass out, that is an indication I am still in the range of safe practice. Anecdotally, I know many people who have spent their lives doing breathholds, and they dont seem any worse for wear.

Are there any high quality studies that look at potential brain damage prior to loss of consciousness?

Does this help? I am a physicist with interest in these subjects and have always been wary of breathwork because of tetany and the following studies. What do experts closer to this field make of these?

[1] "Brain Damage in Commercial Breath-Hold Divers" https://journals.plos.org/plosone/article?id=10.1371/journal...

[2] "Do elite breath-hold divers suffer from mild short-term memory impairments?" https://cdnsciencepub.com/doi/10.1139/apnm-2017-0245

Ref. [2] is especially concerning to me in pushing in any sort of static apnea training or breathwork: "The time to complete the interference card test was positively correlated with maximal static apnea duration (r = 0.73, p < 0.05) and the number of years of breath-hold diving training (r = 0.79, p < 0.001)."

Could you please explain more about the Ref[2], what does it mean beyond what is in article and how serious is it? "These findings suggest that breath-hold diving training over several years may cause mild, but persistent, short-term memory impairments"

Can you tell more about recreational nitrous oxide and when does the "damage occur"? Is there the same thing with wim hof? (like for example with oximeter 80 Sp02 or below?) I got in wimhof/oxide around 80 Sp02 the interesting thing is I got this feeling with fighting to hold my breath but below 90 I kinda needed to convince myself that I should breath in both cases,

Being a non-expert I can't attempt to speculate on your questions in good faith! All I was suggesting to the parent is that perhaps these articles offer as evidence of damage being done without pushing to the point of unconsciousness? Feedback is definitely welcome by an expert.

Key difference here is that freediving is apnea-induced hypoxia, whereas breathwork is literally the opposite: hyperventilation-induced hyperoxia.

So while interesting as a study, I don't think it offers any insight into the kind of breathwork described in the nature study.

Thank you, this is terrific! Why should tetany be worrisome?

In a medical setting, where I am more familiar with it, tetany is never good. Personally it is also wildly uncomfortable. Perhaps it's fine and somehow pushing through it is part of the "experience", but if I want an altered consciousness I'll stick to a psilocybin-based retreat every 5-10 years and my meditation practice in between :D.

yeah in a medical setting it's usually never good, but afaik it's not the tetany that doctors are worried about about but rather what's causing it.

I did a longer write-up on the physiological effects which you might find interesting: https://docs.google.com/document/d/1RuDv_E9osM1CCFWZMywMru9J...

Is this the same thing you linked upthread? At first glance the URL looks the same.

Yes, sorry for crossposting, just seemed relevant here

No worries!

It is definitely uncomfortable and can produce at least minor injuries; I was wondering if there were other reasons to worry.

So the tetany in breathwork is generally caused by the decreased CO2 concentration causing respiratory alkalosis (ie blood gets more alkaline and has a ph balance of > 7.5), which in turn causes the protein albumin to bind more strongly to calcium and not release it as it's supposed to, and calcium is an important regulator in voltage gated ion channels in neurons.

Long story short, your neurons get just a tad bit more excitable because calcium that usually acts like the bouncer to the hot club is busy snogging albumin. That has very little effect in places in the body, but in motor neurons that control your smallest muscles (face and hand), and in sensory neurons under your skin it does move the needle — that causes the muscles to contract and your skin to feel tingly, both exactly the same cause.

This is the reason people with epilepsy should _NOT_ do breathwork, but for otherwise healthy adults there are no negative long term effects of respiratory alkalosis — a few normal breaths to balance out your co2 and the symptoms will go away.

I've done breathwork for years, and at some point the tetany simply stopped happening and hasn't returned.

This is a bit off topic, but what do you think about people doing nitrous recreationally? It's always concerned me that people are inhaling close to pure nitrous oxide and holding it in. I've always wondered if this creates damaging low-oxygen conditions without the normal reflexes kicking in, and if this can cause brain/neuronal damage.

I believe in medical settings it's delivered in a mixture with O2, but in recreational settings it's usually inhaled directly.

I see a lot more talk about the risks of vitamin B12 depletion, and not much talk about O2 deprivation, so not sure if everyone else is crazy or if it's me who is the crazy one.

I was being treated with nitrous medically. I asked the anaesthesiologist about how it works recreationally and his answer was that yes, it was mostly just hypoxia.

Bullshit. You aren't supposed to be hypoxic when using nitrous. You take a half-breath of air, and then breathe in the n2o.

So, you get half the oxygen needed and somehow doing so doesn't cause hypoxia, which means “deficiency in the amount of oxygen reaching the tissues”?

You don't get half the oxygen. You get as much oxygen as you would during normal calm breathing, which is pretty shallow. Basically, you take a normal breath, which is about 50% lung volume, and then fill your lung up to max capacity with n2o.

But you know what? Pulse oximeters are pretty cheap nowadays. Try it for yourself.

I see. So, you take a normal breath and top it up with N2O. That makes sense.

This is easily falsified by a cursory internet search about the physiological mechanism behind nitrous oxide's effects. It is appalling that a medical professional would so confidently give you an uneducated, crackpot answer. The exact same mechanism which knocks you out gives you euphoria at lower doses.

If someone holds their breath long enough to cause hypoxia when inhaling nitrous oxide, they have other problems. You can easily hold your breath 1-2 minutes while sitting on a couch without experiencing hypoxia. If you're experiencing euphoria as strong as what nitrous oxide causes from hypoxia, you're basically about to die.

This is why you shouldn't trust experts on stuff outside their speciality, this answer is just wrong.

You don't even need to research it, the lived experience of being in a dentist office with mixed oxygen and nitrous produces the recreational effects - if it was mostly hypoxia, having oxygen mixed in would have a greatly diminished "recreational" effect.

I mean, it is true most people doing it recreationally are giving themselves mild to severe hypoxia, but that doesn't mean the effect is caused by hypoxia

I'm not one to tell people not to have fun, but i also lost a friend to respiratory failure after prolonged nitrous abuse, and had more then one start having auditory hallucinations. I think it's waning in popularity compared to 10 years ago, but maybe I'm just out of touch with what the kids get high on these days

In zero tolerance Sweden, nitrous is oddly perfectly legal. In fact, I recently got a cheerful flyer from our municipal waste disposal company announcing that empty 1L nitrous bottles can now be left with common household hazardous waste.