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O2 levels

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Aug 5, 2002
I made some testes (not seriously), with a machine which measure the blood O2 level. So I got something like this:
97% when breathing normally and 80% after 3 min of dry static apneea. Actually these values do not have any sense for me... Is anybody so kind to share me some info...like what happen at different levels, what is the lower limit... and things like this.
Where did you measure the HbO2? Hopefully in your earlobe.

The numbers can be useful for personal training as you may begin to see at what point you get close to, or reach, blackout. Eric Fattah has done similar test on himself and I think (help us out here Eric) he has managed to get down to 11% saturation whilst still concious. I doubt many people could get below 50% without lots of training.

CO2 level

the biggest problem for Freediver is not the O2 level but rather the CO2 level. At a certain level of CO2, the brain stop working and you suffer a black out. The CO2 level is also what trigger the breathing reflex, not the low O2 level.
The CO2 DOES trigger the breathing reflex, but surely the low O2 level causes the blackout? The brain shuts everything non vital down when the O2 level gets too low, to conserve as much of the remaining O2 as possible. Never read/heard of the blackout being caused by the build up of CO2. I could be wrong, dunno.
But my biggest problem is the buildup of CO2, that breathing reflex is a bitch to fight ;)
CO2 vs O2

CO2 buildup can also cause a blackout, but it is far less common than a low O2 blackout, because CO2 blackouts cannot occur during breath-holds at atmospheric pressure--if you want to experience a CO2 blackout, you either need to do apnea at extreme depth (and stay there), or you need to inhale pure O2 at the surface, and neither are recommended!

If you just do apnea at atmospheric pressure, you will blackout from low O2 long before your CO2 level reaches 'blackout' danger levels....

Eric Fattah
BC, Canada
Hi Ben,
I measured it with a device attached on my finger. It use spectromeatry to determine the saturation of oxigen in blood. Do you think there is a wrong place to measure O2 level? 11% sounds very low for me...it is possible to use another reference for the satturation(?).What I can say by my own, is that in the first two minuts the level decrese very slow,(to 90% or something) then in the third minute it decrese to 80%, mostly in the last 20 seconds, when I have experienced strong contractions. Also I saw that the hart rate was increesed during contraction, and it should be the reason for the accelerated O2 level decrees. It will be interested a graphic with relations between time(and contractions moments) , O2, hart rate ...maybe I'll do it next time..:)
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