Hyperventilation good or bad

[amihov]

I have been reading in the last few weeks about hyperventilation. And something in the theory about it doesn’t make sense. According to most of the forms and the books I have read if you are hyperventilating your body is not building up more oxygen in the blood but it is just loosing all the CO2. The problem I found in this idea is very simple, in the blood the CO2 carear is the hemoglobin in the red blood cell. The hemoglobin release the CO2 in the lungs and bind itself whit oxygen. What is contradictive in the theory of hyperventilation is that by reducing the CO2 level in the blood we are not getting any extra oxygen. But every time when the hemoglobin release the CO2 in the lungs it binds again to oxygen. We all know that when somebody is hyperventilating he is breathing faster and deeper - he is moving more air throw the lungs and heart rate goes up so we have more blood running true the lungs. According to the simple logic the oxygen level in the total volume of the human blood will go up and the CO2 level will go done, because they use the same carrier in the blood – hemoglobin.

[sheepeck]

In simple words - problem is that you NEED the CO2 in your lungs when diving - that's the trigger which is telling you when to go up and breath = without sufficient level of it you simply won't feel urge to breath or you will feel it too late and BO and drown. Thus - hyperventilation is bad.

[efattah]

Hyperventilating DOES store extra oxygen. But you can't necessarily USE that extra oxygen, because with low CO2, your blood becomes too alkaline. Hemoglobin, in an alkaline environment, doesn't want to release the oxygen bound to it.

Hypeventilating stores extra oxygen in the lungs and the venous blood. The arterial blood is not affected. In the lungs, you only get a few more percent O2, but the O2 saturation of the venous blood increases dramatically with hyperventilation. But, again, with excessive alkalinity from low CO2, the O2 will not be used. Blackout will occur while oxygen levels are still high.

With high CO2 you can withstand a much lower O2 level before a blackout.

[amihov]

I am sorry about the question .
I wonder if you can feel when you have dropt the CO2 level to low during ventilation?

[cdavis]

Good question, its not an easy concept to understand. Excessive hyperventilation will drop your co2 level so low that your carotid arteries contract, reducing blood flow to the brain and you see stars, tingle, etc. That is probably far below the level of co2 you should dive with.

Another off the wall idea. If hyperventilation can increase o2 supplies, could you make those o2 supplies available by breathing a gas mix of higher co2, assuming you could get the mix right? Maybe rebreathe the same air for the last few breaths?

Connor

[amihov]

I am sure that there is a way to feel or notice the moment when you should stop whit the ventilation and start the dive. Many people know it but are they willing to tell or not.

[efattah]

I hypothesized that it would be possible to hyperventilate (& increase O2 storage), after drinking a lot of soda pop. Then, at the end of the static, 'burp up' the CO2 and put it into your lungs. By the end of the breath-hold, the volume in the lungs has shrunk, allowing the CO2 to fit in there.

The soda pop CO2 burp method is 100% CO2 and creates instantaneous contractions if you try it, even without holding your breath first.

[cdavis]

This, I gotta try.

Connor

[Walrus]

In answer to the original question I don't think that hemoglobin is actually the primary carrier for CO2 in the blood, there are at least 3 paths. CO2 dissolves in liquid much more then O2 does so part of it is in the blood plasma and probably other body tissues. You also have the blood buffers ie HCO3, from what I understand this stores more CO2 then what is bound by the hemoglobin.

It makes sense to me otherwise why can you recover blood oxygen so much faster then get your CO2 levels back to resting after a breathold ?
If you look at a pulseoximeter graph of someone doing a breathold, you recover most of your blood O2 in the first 10-20 seconds. It seems to take most people quite a few minutes to feel they are ready to hold their breath again.
Offgassing the CO2 from the HCO3 buffers and from what's dissolved in liquid is a much slower process. I tried to find a reference to it, found something but may not be completely in line with a hypoxic scenario so don't know if those percentages are right, but gives you an idea at least:-



1) 1.5% O2 dissolved in blood
2) 98.5% O2 carried by hemoglobin (Hb-O2)
a) Hb can carry up to four molecules of O2 (four = saturation)
b) Po2 determines Hb saturation
c) also pH, temperature and Pco2 affects Hb-O2 binding
d) ** review O2-hemoglobin dissociation curves for Po2, Pco2, pH & temp.
e) "Bohr effect" describes oxygen unloading (dissociation) where low pH exists
i) enhances oxygen delivery in tissues with increased metabolism
3) 7% CO2 dissolved in blood
4) 23% CO2 bound by Hb
5) 70% CO2 in form of HCO3-


Cheers,
Wal

[amihov]

Thank you Walrus. Thank you every body for participation. I believe that this is important topic and it is good idea to share knowledge about it . It will be safer for everybody if we better understand this.
The information is very helpful.
It seems like if you do short hyperventilation before the dive for maybe 20 sec you will be able to max out the oxygen level and still have plenty of CO2 in your body. This way you will be able to take advantage from the hyperventilation whit taking a big risk.
Sasho

[amihov]

I have made a speling mistake it has to be without taking a big risk.

[cdavis]

Thanks Wal, fascinating numbers, especially the HCO3 buffering. I think that explains much of why tolerance training works so well.

Not in any way disagreeing, but how does slow off gasing of co2 square with short surface intervals leading to BOs from low 02? It almost seems like it is a two stage process, you get most of your 02 back very quickly, but to fully replenish 02 levels takes longer than getting rid of co2.

Connor

[naiad]

So more HCO3 buffers means less dissolved CO2, therefore less lowering of pH, therefore less Bohr effect? Maybe having good CO2 tolerance (more buffers) means that hyperventilation will have a greater effect on O2 availability?

I don't do heavy hyperventilation, and I hardly ever breathe up for more than 2min. This works best for me. My CO2 tolerance is normally quite good, and very good if I have done lots of tables.

[XabreTooth]

Which part of the blood CO2 triggers the urge to breathe? the dissolved fraction or the bicarbonate (HCO3) fraction?

I assume it's not the fraction bound to Hb.

[naiad]

I think it's the dissolved fraction, as this lowers the pH of the blood.