CNS Toxicity Living at Altitude

[Spikester54]

I am studing for my Nitrox certification, and read about CNS Toxicity as a result of too much exposure to oxygen and diving, and too keep it to below 1.4 pp. It also stated that the % of Oxygen at sea level is 21%. I have two questions.

1. Living and exercising at 9100 to 11000 feet year round, what is the oxygen content of the air I breathe ever day? It must be less than 21%, because of all my friends and family who visit who cant breathe.

2. Because I live at higher altitude and do not require as much oxygen, am I more suspetible to oxygen toxicity?

Just checking, want to make sure on my first Nitrox dive, that the safe settings on my computer for sea level, as still safe for me.

Thanks for your time.

 

[DocVikingo]

You are neither more nor less susceptible.

Regards,

DocVikingo

 

[Spikester54]

Thanks

 

[Charlie99]

1. Living and exercising at 9100 to 11000 feet year round, what is the oxygen content of the air I breathe ever day? It must be less than 21%, because of all my friends and family who visit who cant breathe.

DocVikingo answered your question but I'd like to point out that the air you breathe has the same percentage of O2 as the air at sea level, and the same percentage of O2 that is in a tank of air compressed to 3000psi, and the same percentage of O2 as air being breathed at 100' depth. What does change in each case is the partial pressure of O2.

After your nitrox class, you should understand the difference.

 

[fppf]

After your Nitrox class look into the EVA procedures that NASA uses.
Just one of those things that make you go "huh, thats neat"

 

[rakkis]

People that visit you can't breathe because their body doesn't have as many red blood cells as yours. Yours has adapted to the lower ppO2 and makes more RBCs to compensate.

 

[DocVikingo]

DocVikingo answered your question but I'd like to point out that the air you breathe has the same percentage of O2 as the air at sea level, and the same percentage of O2 that is in a tank of air compressed to 3000psi, and the same percentage of O2 as air being breathed at 100' depth. What does change in each case is the partial pressure of O2.

After your nitrox class, you should understand the difference.

HiCharlie99,

Since it's been a very, very long time since my certifications, your concluding remark prompts me to ask, "Do certifying agencies no longer introduce Dalton's law and the notion of partial pressures of gases at the BOW and AOW levels of training?"

Thanks,

DocVikingo

 

[Charlie99]

Since it's been a very, very long time since my certifications, your concluding remark prompts me to ask, "Do certifying agencies no longer introduce Dalton's law and the notion of partial pressures of gases at the BOW and AOW levels of training?"

For BOW and AOW it's all about air, so there isn't much reason to get into partial pressures. I don't actually recall whether or not it was covered in my private cert class. After I commented "duh. pV=nRT" we moved on to the next section.

 

[texdiveguy]

After your Nitrox class look into the EVA procedures that NASA uses.
Just one of those things that make you go "huh, thats neat"

I have looked at just a wee-bit of the NASA/EVA 'tests'....pretty kool stuff.

 

[cwilson]

This subject has not been well researched. There is no definitive evidence that high altitude adaptation increases the risk of oxygen toxicity in humans. But this lack of evidence is only because the subject has not been studied very much. A 1975 paper in the journal of applied physiology did show that mice acclimatized to various altitudes (5,000 ft - 15,000 ft) had a decreased time to convulsion, and that the longer the duration of acclimatization, the shorter the time to convulsion. Journal of Applied Physiology 1975 Feb;38(2):279-81

Oxygen toxicity in the altitude adapted person is likely affected by a complex interplay of increased hemoglobin, increased 2,3 DPG, neovascularization (increased capillaries), altered carbon dioxide / base buffering, and various other physiologic and biochemical changes. The net effect of these changes on 02 toxicity is not well studied.

The current limitations on depth vs 02 toxicity are based on a population that is inevitably biased towards average, non-altitude adapted people. Altitude adaptation very likely DOES have at least some effect on a person's susceptibility to o2 toxicity.

ANYONE who deviates from the norm should leave an extra margin of error for themselves!