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Comment by phonypc | Hacker News Reader

There's no buildup of CO2 with these breathing techniques. Quite the opposite.

Can you please elaborate. If you hold your breath and don't exhale for a longer period there will be CO2 buildup in the body.

It’s probably more accurate to say there’s a build back of CO2. Wim Hof uses hyperventilation to lower blood CO2 level well below normal so that when you do the breath hold, a big chunk of the time is spent just returning CO2 to that normal level.

This is in contrast with other breathing exercises to do cause an actual build up of CO2 to levels well above what feel normal. Freedivers call these CO2 tables and they’re used to build CO2 resistance and increase breath-hold times.

Scroll down a bit. There’s a section explaining what happens.

https://www.wimhofmethod.com/breathing-exercises

“When we breathe in, we take up oxygen and release carbon dioxide from our blood. Our blood is usually already fully saturated with oxygen (about 99% saturation) and breathing deeply does not raise that saturation. Breathing deeply does, however, release a lot of carbon dioxide. This, in turn, lowers the “urge to breathe”.

The brain stem, specifically the pons and medulla oblongata, is sensitive to carbon dioxide. Having too much carbon dioxide in the blood will trigger your brain stem to breathe. By removing carbon dioxide from the blood through deep breathing, this impulse to breathe from the brain stem is lowered.

In short, the lower the level of carbon dioxide, the longer you can hold your breath. The impulse is just not triggered yet.“

The explanation seems contradictitory. Initially it says "Breathing deeply does, however, release lot of CO2". Later it says "By removing CO2 from the blood through deep breathing ....".

It's confusing to me too because if the blood is 99% saturated with oxygen is there only 1% CO2? Is hyperventilating getting to 100% or further?

Are we talking about the same numbers as a (calibrated) O2 optical saturation monitor reports or something else?

Hyperventilation doesn't significantly increase blood oxygen saturation. A healthy person near sea level will already be close to 100% so there's no room for increase. This is normally measured using an optical sensor.

Blood O2 and CO2 percentages don't sum to 100%. O2 saturation refers to the percentage of hemoglobin molecules which have oxygen bound. Only some CO2 is transported bound to hemoglobin.

Releasing CO2 from the cardiopulmonary system is removing it from the blood, no contradiction.

And how does deep breathing remove CO2 from the blood?

Breathing removes CO2 generally. But when you are breathing normally, i.e. letting the autonomic nervous system control the breathing rate at tidal volume (the amount of air exchanged in a normal breath), the rate of purging CO2 is equal to the rate it is produced by cellular respiration so you have a normal physiological amount of CO2 in circulation.

If you intentionally breath deeply, greater than tidal volume, it means at the same breathing rate, you are exchanging more air in total and will be purging more CO2 than you produce which will lead to hypocapnia over time.

Hypocapnia doesn't inherently need to result from deep breathing if you offset the greater-than-tidal volume with less-than-normal breath rate — if you are breathing very slow or 'skip' breathing with pauses in between, but that balance can be pretty hard to reach

This won't happen if you are holding your breath, right.

Depends on the balance of deep breath and breath hold. At the end of the day if the overall air exchanged is greater than necessary to maintain balanced CO2 levels, for example if you are deep breathing and pausing in between but not long enough to offset the amount of air exchanged, you could still be driving a net decrease in CO2 levels. However if you are breath holding until the urge to breath arises, which is driven by rising CO2, then yeah you are probably offsetting the effect of the deep breathing.

To expand it can be better understood looking at the Bohr Effect [0]. It's related to the efficiency of unloading the oxygen the body has access to.

[0] http://www.pathwaymedicine.org/bohr-effect

This seems incorrect. If your body burns O2 without breathing you will inevitably end up with more CO2.

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