air consumption versus depth

[Piscean]

Hmm, just reading this and the one question that remains unanswered for me is why we get winded at altitude. Perhaps up there we don't get so much oxygen, but that doesn't have anything to do with our desire to breathe, that comes from CO2 but if we are not getting enough O2 surely we can't produce much CO2 to make us need to breathe so why do we get out of breath so fast?

 

[Jimmer]

Hmm, just reading this and the one question that remains unanswered for me is why we get winded at altitude. Perhaps up there we don't get so much oxygen, but that doesn't have anything to do with our desire to breathe, that comes from CO2 but if we are not getting enough O2 surely we can't produce much CO2 to make us need to breathe so why do we get out of breath so fast?

In this case I believe it does have to do with lack of O2. Athletes that train at altitude end up with higher levels of Hemoglobin and red blood cells to adapt to the lower amount of O2 there. My understanding of it would be that at the cellular level, it is excess CO2 in the form of Lactic Acid buildup in the muscles, and the muscles demand that O2 be delivered to flush it out.

 

[Warren_L]

I suppose I can post in this thread once every 3.5 years. Being winded at altitude is related to lower partial pressure of oxygen. If you look at climbers that climb everest - many of them bring oxygen with them so that they don't get as winded. I'll be back on this thread sometime in 2010.

 

[rawls]

In this case I believe it does have to do with lack of O2

The percentage of O2 is the same regardless. You don't have a lack of O2...You have a decreased partial pressure of O2...

 

[JeffG]

I suppose I can post in this thread once every 3.5 years. Being winded at altitude is related to lower partial pressure of oxygen. If you look at climbers that climb everest - many of them bring oxygen with them so that they don't get as winded. I'll be back on this thread sometime in 2010.

Maybe they were winded because it was a hard climb.

 

[mikerault]

The air is thinner (lower pressure) therefore the number of molecules of O2 available for exchange is less (if the density of air is 50% less, then the number of O2 molecules is 50% less, regardless of the fact it is still 21% of the reduced density) so less is exchanged, hence you get winded and breath heavier.

The surface area of the lungs and the amount of transfer agent (hemoglobin) stays constant, the amount of O2 to exchange decreases, you have to increase the amount of O2 going past the lungs surface area by breathing harder and increase the flowrate of the transfer medium (blood flowrate) to get the same amount of transfer...

Mike

 

[Piscean]

Jimmer,
I like the lactic acid theory in that it is acid and we know the desire to breathe is driven by acid but I thought the cause of muscle stiffness is also lactic acid and that often comes along two days later so I'm wondering why I wouldn't be breathing like a madman for two days due to residual lactic acid.

Mikrault,
I get the less oxygen thing, but that's exactly what is confusing me. Half as much oxygen = breathing twice as fast you say (or at least faster) so why doesn't twice as much oxygen mean breathing slower (and therefore a reduced air consumption at depth which we know doesn't really happen from your other thread)? And anyway, decreased oxygen doesn't mean breathing faster by itself, this page http://www.ismmed.org/np_altitude_tutorial.htm talks about having to consciously remind oneself to breath because lack of oxygen is not much of a driving factor, but instead, lack of CO2 means the desire to breath is reduced.

So what am I missing?

OK, I found what I'm missing - isn't Google fantastic? So it seems the reason none of us know about it is because it has only been understood since about 2001. Apparently it is related to some things called S-nitrothiols which trigger receptors in the brain to cause us to want to breathe even without lots of CO2. Here's the abstract: http://adsabs.harvard.edu/abs/2001Natur.413..171L
I didn't want to pay the money for the whole article, cheapskate that I am. So I hope you don't feel I've wasted your time when I could have just searched in the first place.

 

[IwakuniDiver]

Piscean,
I have been following this thread since it started the other day and I thought I might chime in as well.

I know all too well what it's like to wrap your mind around a problem that's really annoying me. One of the things that I have found most of the time is that I spent most of my time thinking so hard on the complex logicals of a problem that I sometimes overlook the simple truths.

Ask yourself this; Have you ever breathed 100% O2 before? Say, in a hospital? If your line of reasoning is correct, you should be able to slow your breathing down to 25% of your normal rate while maintaining normal activity since you're used to getting only 21% normally. Your breathing didn't rate didn't change much did it? Nor will it. Here's why, (physicians in the house help me out here if I miss anything or get something wrong.)

Your body is only capable of using so much O2. Now what that level is depends heavilly on your body and what demands you are placing on it. You read in that link you posted (I read it too), the breathing reflex is usually triggered by elevated levels of CO2 in your body. So, think about this logically, if your body can really only use a max of say, 21% O2 (at a resting state), you could breathe 100% O2 (at a resting state) and your body will still produce the same levels of CO2 as you were before and hence triggering your breathing reflex at the same intervals.

Now that's just the extreme basics of the biology of breathing. Take into account the psychological side of breathing and we'll have another 50 page thread in here.

Cheers!

 

[Tigerman]

Apparently the amount of hemoglobin or the transport of the hemoglobin is the limiting factor in o2 uptake. This makes sense: sporters often train a period in the mountains. The body responds by making more of the hemo stuff. When going back to sea level the sporter performs better :lifter: because he is able to supply his muscles with more oxigen (a more lousy sporter would just get drugged to have the same effect :HAHAHA: :shame: ).

Would be interesting to put a diver in the mountains for a while. Having more hemoglobin would mean the diver is able to extract more o2 from a breath before the co2 level forces him to exhail :errrr: . However, he somehow has to do something with the o2. Doplers excercize

I currently live at ~1000 feet above sea level and Im in decent physical shape. Im somewhat of an air hog. However, thats probably related to my limited experience more than anything else
Ive been living even higher before, well above 1500 feet..

 

[PaulChristenson]

http://home.earthlink.net/~divegeek/primer.htm