[sigmoid10]

You can't get "oxygen high" from breathing normal air. The O2 levels will always stay the same unless you stop breathing for a while. What will make you feel weird in the head when breathing too fast is the reduction of CO2 in your blood.

[dmos62]

So, if you breathe in an intensive manner for a few minutes, oxygen percentage in the blood won't change?

[n8henrie]

One a friend and I hooked ourselves up to continuous pulse oximetry and had a contest to get the lowest recorded oxygen level. We tried everything we could think of, from just holding our breath to end-expiratory breath holding to hyperventilating to clear O2 (I used to do some recreational free-diving) beforehand to exercising (jumping jacks)...

Neither of us could get it below 98%, and this was at a mile of elevation (UNMH in Albuquerque).

[sigmoid10]

It is pretty easy if you use the Wim Hof method. Breathe deep and fast for a few minutes, to the point where you get dizzy or feel weird sensations. Then exhale and stop breathing while being fully relaxed. I've done this while hooked to a pulse oximeter and it takes quite a while before O2 actually starts dropping (especially because the effect can be delayed in your limbs), but once it starts you'll pretty quickly run into the regime where a normal oxi will start an alarm because O2 is too low. You can even go below 85% without losing consciousness, because your limbs will desaturate faster than your brain. It's also not uncomfortable, because rising CO2 is what causes breathing reflex, but you dropped its levels far below the threshold by hyperventilating first.

[n8henrie]

Interesting. As I noted above (though typo O2 -> CO2), I used the same technique you describe, which I learned in free diving, and was not able to get below 98%, at altitude.

[sigmoid10]

I'm quite sure no freediving instructor would ever teach you this particular method, because it is a surefire way to die underwater on your first attempt. Free diving breathing techniques usually revolve around lowering your heart rate, not lowering CO2. Wim Hof trainers will also tell you to never to use this method when near water.

As for the specifics that may have prevented you from doing what you wanted: If you breathe too shallow or too slow, you won't clear enough CO2. In freediving this is normal (even wanted), but for Wim Hof practice it means you didn't do it right. You really have to breathe so deep and fast that you enter an uncomfortable zone. It's not unlike physical exercise, except it's mostly mental.

[n8henrie]

> I'm quite sure no freediving instructor would ever teach you this particular method, because it is a surefire way to die underwater on your first attempt

Definitely no instructor involved, just a dumb 20 year-old living in Puerto Rico. It admittedly was dangerous, but I am living evidence that it was far from a "surefire" way to die. It was one of a hundred ways in which I put my life at risk during my 20s. ¯\_(ツ)_/¯

> As for the specifics that may have prevented you from doing what you wanted: If you breathe too shallow or too slow, you won't clear enough CO2.

I'm confident I was doing it sufficiently well to accomplish a longer period of breath holding than I otherwise would have been able to sustain, as evidenced by having done so (in addition to the usual symptoms of lightheadedness, confusion, loss of vision, near-syncope -- yes I agree quite uncomfortable). I know people on HN love to idolize Wim Hof, but in this context minute ventilation is not that difficult of a concept; I'm usually able to estimate the response in a paralyzed patient's PCO2 fairly well when making changes to their tidal volume and rate.

I didn't search for too long, but here's at least one relevant document, in which otherwise untrained subjects were able to achieve a substantial reduction in CO2 (17.4 vs 29.0) with a mere 15 seconds of hyperventilation, leading to an extra 23 seconds of breath holding prior to involuntary breathing moments. The peripheral O2 sat nadir in the hyperventilation group appears to have been identical to the non-hyperventilation group after the first trial (Fig 8b, looks like ~94%) and was only statistically significantly lower on trials 2-5: <https://pmc.ncbi.nlm.nih.gov/articles/PMC10363065/>

[ambicapter]

I got a pulse oximeter during COVID and was able to get my O2 levels to spike down to 64% using Wim Hof breathing (for less than a second, ofc).

[stoorafa]

Can’t claim to know for sure, but I’d assume some kind of measurement limitations: the resolution and upper/lower limits of pulse ox are probably calibrated to some medical need, not to detect changes beyond what’s medically necessary

[n8henrie]

This was using equipment in the emergency department of our state's only L1 trauma center and comprehensive stroke center; I presume it was decent as far as medical monitoring equipment goes.

[jcul]

If you've ever done the wim hof breathing method, it is a very intense experience.

Basically hyperventilation + long breath holds. Probably similar to what free divers do without the mammalian dive reflex due to the cold water. Or like a dangerous game kids used to do when I was in school where you hyperventilate and then have someone press on your chest until you pass out.

But anyway, I'm not sure if the science would back it up, but Wim Hof describes it as over oxygenating the blood and then stopping and letting CO2 ramp up or something. Whether it is significantly dropping the CO2 or increasing oxygen during the hyperventilation phase, isn't it kind of the same thing? Adjusting the ratio.

Anecdotally, when I was doing it regularly I seemed to not get sick at all.

[thfuran]

Blood oxygen saturation is always near 100% in a healthy person. 95% is the low end of normal. Dropping to 90% is considered hypoxemia, and 80% is a medical emergency. So there really shouldn’t be any room to increase it significantly.

[n8henrie]

In many people a momentary drop to the 80s or even below is not an emergency or anything close to it. Not saying that it is good. Someone that is awake, sitting up, and struggling to breathe should be considered an emergency regardless of oxygen levels (and in this situation 80% would be very concerning).

EDIT: your comment is otherwise entirely correct, particularly at sea level.

[TylerE]

90% you should really be traveling to see someone. At least an urgent care, if not an ER.

[cenamus]

No it would stay at pretty much 100% (as is normal). But co2 goes down, which lessens the ability of oxygen to come out of the blood. That's why you get dizzy when hyperventilating

[TylerE]

Nope. The blood is already fully saturated with oxygen (in a healthy-ish person) at rest. Even intensely breathing pure o2 can't give you a saturation higher than 100%.