air consumption versus depth

[Piscean]

Tigerman - do you really mean only 1,000 ft? That's about the height of the Empire State building but not enough to count as living at altitude. To count as living at altitude I think you need to be more like at 5,000 ft or even 10,000 ft.

Iwakuni - actually I once breathed 300% oxygen (100% O2 at 3 atm) in a hyperbaric chamber. The question [which revived this thread] was really about why we get winded at altitude (i.e. when O2 is depleted) - the answer to that lies in S-nitrothiols which alert the brain that we are short of O2. At depth (i.e. when O2 is enriched) the reason we don't get extra air time is because it is a different mechanism causing us to breathe - increase blood pH due to CO2 - this was explained by others (Doppler) and you in this thread.

Physiologically I think it makes sense - our bodies have to protect us against two bad situations:

1) not enough O2 (hypoxia) which leads to dead brain cells or dead everything if it stays that way too long.
2) too much CO2 (hypercapnia) which leads to muscle twitching and eventually unconsiousness and death. http://en.wikipedia.org/wiki/Hypercapnia

For each situation there is a preventative mechanism which is necessary because the mechanism for too much CO2 does not ensure sufficient O2 and the mechanism which prevents too little O2 does not prevent excess CO2.

 

[Tigerman]

Tigerman - do you really mean only 1,000 ft? That's about the height of the Empire State building but not enough to count as living at altitude. To count as living at altitude I think you need to be more like at 5,000 ft or even 10,000 ft.

Iwakuni - actually I once breathed 300% oxygen (100% O2 at 3 atm) in a hyperbaric chamber. The question [which revived this thread] was really about why we get winded at altitude (i.e. when O2 is depleted) - the answer to that lies in S-nitrothiols which alert the brain that we are short of O2. At depth (i.e. when O2 is enriched) the reason we don't get extra air time is because it is a different mechanism causing us to breathe - increase blood pH due to CO2 - this was explained by others (Doppler) and you in this thread.

Physiologically I think it makes sense - our bodies have to protect us against two bad situations:

1) not enough O2 (hypoxia) which leads to dead brain cells or dead everything if it stays that way too long.
2) too much CO2 (hypercapnia) which leads to muscle twitching and eventually unconsiousness and death. http://en.wikipedia.org/wiki/Hypercapnia

For each situation there is a preventative mechanism which is necessary because the mechanism for too much CO2 does not ensure sufficient O2 and the mechanism which prevents too little O2 does not prevent excess CO2.

Being on 1000 feet 24/7 and doing all your training and other physical abilities at that altitude AND ABOVE is a far different thing than visiting or working on the top of the empire state building to begin with..
And yeah my appartement is at "only" 1000 feet, but if i go for a 15 minute run im at 2000+ feet, so you go figure out for yourself how it looks here..

Hint: its not exactly the netherlands

 

[Piscean]

Tigerman,

I wasn't suggesting that anyone take up residence at the top of the Empire State building, it was just supposed to help discern 1,000ft from 10,000ft which is sometimes tough if you've had a couple of beers .

Anyway, I checked here: http://bpesoft.com/s/wleizero/xhac/?M=p and found that being at 1000 ft means you have ~4% less air pressure than at sea level. Assuming it's a linear function that means you'd have ~4% lower air consumption. If it's quadratic you'd be looking at something like 8% less (0.96*0.96=0.9216). At least for me that would not be noticable as reduced air consumption (stress/cold causes +/-20% swings for me). I've heard before that being fit means your lung volume is used more efficiently meaning deeper breaths and therefore more air and your muscle mass is higher so you use more oxygen. Perhaps that is why you use more air than you expect.

I live close to sea level (200ft), but don't notice a difference in how easy it is to breathe at the top or bottom of the mountains near where I live where I can go to ~3000 ft (0.90 atm). In Nevada however when I was at 6000 (0.80 atm) or 7000 ft (0.77 atm) I did notice a difference so I'm just saying, based on my experience I don't expect being at 1000ft to make much of a difference.

In addition, unless you go diving with people from the Netherlands, I'm sure all of your dive buddies live between zero and 2000ft say above sea level so you'll be right in the middle. I'm just not convinced that 1000ft is high enough to make a noticeable difference compared to say you going for a 15 minute run and your buddy taking his car. I think that would make much more difference.

Back to the fitness thing again, if you are fit, you will mostly get your energy from aerobic respiration which produces CO2 and that in turn leads to the desire to breathe. On the other hand, if you are not fit or your blood cannot transport enough O2 to your muscles you will instead respire anaerobically generating lactic acid but no CO2 (http://en.wikipedia.org/wiki/Anaerobic_respiration) and therefore a reduced desire to breathe. One could postulate quite reasonably, that living at altitude would increase the effectiveness of oxygen transport by the blood due to more haemoglobin, therefore leading to more aerobic respiration causing more air to be used due to CO2 production. So I suggest to the board, that living at altitude actually causes you to use more air.