Hypercapnia or Hipoxia?

[Polorutz]

I am trying to understand what happens during a breathhold...

I know that what gives you the urge to breathe is hypercapnia or better said, the urge to expell CO2 from the body... but... what If I do residual apnea, you exhale completely then hold your breath, the urge tobreath comes way sooner and I sometimes experience no contractions...

Hypercapnia or Hipoxia? (Lack of o2)

[DeepThought]

From my understanding it can still be both but the chances of hypoxia are greatly increased.

[samdive]

interesting - I bet Alun knows..

I would say still hypercapnia as your metabolism is still working away producing CO2 and thats a much bigger trigger than hypoxia.....

but I could be wrong

Alun? Ben? Eric?

[Alun]

CO2 is stored in your blood and in your lungs. if you make your lungs small by exhaling, then more CO2 must be stored in your blood.... hence the urge to breathe comes sooner.

i think this is the explanation.

[Polorutz]

ok... What I want to do is train myself to be VERY tolerant to hypercapnia and I thought residual stair climbing and walking would do... I really feel the ache on my limbs... the same one you get when surfacing from a deep dive but maybe I was actually not training for co2 but for o2... now I know that It's what I wanted... I will continue to do this since it's increasing the capacity of my tolerance... good to know

[fpernett]

I think that the CO2 level depends on your ventilation prior to a exhale apnea, and the brainstem senses is the CO2 blood levels, so if you make a strong hyperventilation before exhale apnea, it's possible that you BO easily. I think that in exhale apnea is better to hypoventilate or ventilate normally to keep a high level of CO2 and have warnings just from the hypoxia. I think that exhale apnea while climbing or walking has a better effect on hypoxia tolerance, that ache on your limbs means that you are working anaerobically, it's not an effect of high CO2 levels.
I consider exhale diving the most physiological way to train.

[Polorutz]

So I train my anaerobic resistance with exhale exercise... and Hypercapnia? how should I train my Co2 Tolerance?

[samdive]

normal volume breath holds with less and less recovery time between them?

[quasimoto]

i have a question:
is the urge to breathe from the amount of CO2 or from the perntage of it in you lungs? If its the latter, it would explain why you getthe urge to breathe much sooner on exhale breath holds, even though you arent out of oxygen.

any info would be appreciated

[cdavis]

Frank and Sam are right on. To say it another way, the urge to breathe is primarily triggered by decreasing ph of the blood, caused by elevated CO2 concentration. It is my understanding (I could be wrong) that extremely low O2 concentration also increases the urge to breathe. Train for increased tolerance for low O2 by exhale apnea walking or O2 tables or similar. Train for improved CO2 tolerance using CO2 tables, full lung apnea walking, repetitive excercise with short recovery time or similar. Either type of training probably helps both CO2 and O2 tolerance, it just that the area of concentration is different.

Connor

[naiad]

Originally Posted by cdavis

To say it another way, the urge to breathe is primarily triggered by decreasing ph of the blood, caused by elevated CO2 concentration. It is my understanding (I could be wrong) that extremely low O2 concentration also increases the urge to breathe.

I think that both elevated CO2 concentration and extremely low O2 concentration can cause the urge to breathe. I have experienced both separately, although in normal circumstances there would be a bit of both and CO2 would be the dominant one.

High CO2 causes an intense urge to breathe, much stronger than that caused by low O2, but it is more bearable. This is what happens at the end of a CO2 table, or after doing dynamics with short intervals.

Extremely low O2 causes a less intense feeling, but more urgent and unbearable. It usually comes on suddenly and gets rapidly worse, unlike high CO2. This is what happens if I hyperventilate too much before doing a max static. The feeling doesn't always happen, and it is possible to BO without any 'struggle phase'.

Lucia

[wet]

Lucia, did you mean to say "unlike high CO2"?

Originally Posted by naiad

I think that both elevated CO2 concentration and extremely low O2 concentration can cause the urge to breathe. I have experienced both separately, although in normal circumstances there would be a bit of both and CO2 would be the dominant one.

High CO2 causes an intense urge to breathe, much stronger than that caused by low O2, but it is more bearable. This is what happens at the end of a CO2 table, or after doing dynamics with short intervals.

Extremely low O2 causes a less intense feeling, but more urgent and unbearable. It usually comes on suddenly and gets rapidly worse, unlike low CO2. This is what happens if I hyperventilate too much before doing a max static. The feeling doesn't always happen, and it is possible to BO without any 'struggle phase'.

Lucia

[naiad]

Yes. I just changed it.

[naiad]

Maybe I should explain a bit better what I meant. This is what happens if I do a close to max dry static (5:30) with a higher or lower amount of CO2.

If I do my normal breathe-up (moderately low CO2 at the start of apnea):
For the first 3:30 there is no urge to breathe, or any other unusual feeling. From 3:30 to 4:30 the urge to breathe starts very slight and gradually increases. There may be a few contractions after 4:30, usually not very strong. From 5:00 onwards it is difficult, but not excruciating. When I stop at 5:30, I am completely in control, maybe a little bit 'spaced out' but definitely no LMC.

If I hyperventilate heavily (very low CO2 at start of apnea):
For the first 4:00 there is no urge to breathe. From 4:00 to 5:00 there is a definite strange feeling, but no real discomfort. Then suddenly, sometime after 5:00, there is a strong urgent urge to breathe, with strong desperate contractions. If I stop at this point, I will probably feel very 'spaced out' and on the edge of LMC. If I keep going for more than a few seconds after this point, I will LMC or blackout.

I don't know what causes the sudden urge to breathe in this case, maybe someone can explain. I assumed it was hypoxia.

Lucia

[trux]

It is still hypercapnia. Even if you hyperventilate strongly, there still is CO₂ in your lungs and in your blood. The curve of the growing CO₂ level may differ from the case with normal breath-up, and so can also the urge to breath. That's influenced by several factors, including the partial pressure of CO₂ and O₂. The danger of hyperventilating is not that it completely removes CO₂ from your body, but rather that it changes the balance your brain uses for evaluating the need to breath. Besides delaying the growing curve, it can also lead to hypoxia and a blackout at the beginning of the apnea, because the body reacts to the hyperventilation by throttling the carotid arteries and other similar mechanism. When then the CO₂ level starts to grow again, the O₂ level already starts to fall, and the brain instead of switching into the saving mode (mammalian diving reflex), it still thinks there is just the normal level of O₂ (because CO₂ is about normal), hence the mammalian reflex comes later too (if at all).

So, it is certainly possible to make breath-holds after hyperventilation, but besides it being extremely dangerous, it is also quite questionable if it can help you to reach longer breath-hold times at all - on my mind it is quite counterproductive. On my mind the only effect it has (besides the risk factors) is that it helps you to shorten the struggle time, allowing you so to go into deeper hypoxia with less effort and pain, but for the price of possibly higher O₂ consumption.

I'd compare it to painkillers used by some to "cure" diseases - they help you to go over, but they do not cure, and by removing the pain effect they do not even let the body to react to the disease with proper natural self-defense mechanism, so often they aggravate the disease instead of curing you.

If you want to experience deep clean hypoxia without hypercapnia, you'll need to breath helium or another inert gas - I can guarantee you, you'll have no contrations whatsover and will die quite painlessly.