SummitPost.org

Thanks

Generally (at sea level), the heart is the limiting factor in delivery of oxygen to the muscles. The muscles are ready to use more oxygen, but the heart simply cannot pump any faster to get more oxygen to the muscles. (Blood is 100% saturated with oxygen)

At altitude, the reduce pressure of oxygen in the air slows down the rate of transfer into the blood stream. Now, the % saturation is less than 100%. It has nothing to do with fitness; in fact, sometimes being in great shape is actually worse, because the proper workload to not ascend to quickly may actually be mush less than what the person is used to.

You have to improve the ability to transfer oxygen from lungs to blood. And people do that - by hyperventilating. The problem with hyperventilation is the side effects (like dizziness).

Many high-altitude dwellers have chronic hyperventilation.

I dunno. The only thing you can do is go on altitude on a very regular basis. It seems to help me a lot; this is not based on any scientific fact but just personal experience. Somehow my body adjusts much faster with regular altitude exposure.

RayMondo wrote:Apart from all the known technicalities, there remains the unanswered as to why some people who've never been high don't get problems when the well trained do.

Maybe not having smoked so much dope when in college kept their lungs cleaner than those who got high

It's likely there is a genetic link to altitude acclimatisation. Like the newly discovered longevity gene - the extent to which our telomeres can be sustained throughout a lifetime of cell regeneration. Interesting that there is now a drug to support it. TA65 $25,000 for a years supply. Heck, one could do a whole bunch of climbing instead. Natural telomerase is produced by the reproductive organs. So, I'll say no more

<a href=http://http://longevity.about.com/od/researchandmedicine/p/telomeres.htm>Telomeres</a>

<a href=http://http://websites.afar.org/site/PageServer?pagename=IA_b_tel_5_role>US Federation for Ageing Research</a>

I'd have to agree with FortMental. Denali is a dangerous place to have a problem and even more-so if you EXPECT to have one. Further, aside from jeopardizing your own well being, you are exposing your climbing partners to unnecessary risk as they attempt to deal with your condition as it presents itself in brutal conditions. Not to mention the potential of screwing them all out of a shot at the summit. Perhaps $$ is not a problem for you but a voluntary LAMA ride out of the 14 camp will run about $1000.00. To get a free ride you will likely be borderline comatose. If you're going with a guided trip, tell them now about your altitude experience. You seemed to proven to yourself that altitude is not your bag. Denali is no place to test your new fitness regimen. People die there. The only thing predictable is the unpredictability. So don't do it. There are hundreds of other pursuits that will be better suited for you.
If you read FortMental's classic Denali TR, however, you may find the secret to many climbers success above 14 camp, the now famous J&D. (Jaegermeister/Diamox cocktail). Just joking-I doubt that it really works.

Ze wrote:You have to improve the ability to transfer oxygen from lungs to blood. And people do that - by hyperventilating. The problem with hyperventilation is the side effects (like dizziness).

Hyperventilation has absolutely nothing to do with the transfer oxygen from lungs to blood.

Mathematically, we can calculate the aveolar-to-arterial oxygen gradient (A-a gradient):

A-a gradient = (FiO2*(PB-pH2O) - paCO2/R) - paO2

where:

FiO2 = fraction of inspired air (21%)
PB= ambient barometric pressure
pH2O=partial pressure of moisture
paCO2=arterial partial pressure of carbon dioxide
R=ratio of inspired CO2/expired O2
paO2=arterial partial pressure of oxygen

As you can see, variables for respiratory rate or minute volume are no where to be found in the equations.

We can also calculate other measures of oxygen transfer such as oxygen delivery, alveolar diffusion capacity, etc., and none of those equations contain variables for respiratory rate or minute volume.

And don't even try to argue that R is dependent on minute volume. Inspired CO2 is a constant and expired O2 is a function of metabolism. If you want to do the math, calculations of O2 consumption and expired O2 are also not dependent on respiratory rate or minute volume.

You could make an argument that paCO2 is a function of minute ventilation, but paCO2 is small and changes very little from pvCO2 to paCO2 (in relation to the magnitude of paO2), and the factor of paCO2/R is so small as to have a negligible effect on the A-a gradient. Therefore, it would difficult to argue that the A-a gradient depends to any significant degree on the minute ventilation.

Furthermore, at altitude it is the barometric pressure that determines arterial oxygen saturation, not the respiratory rate. The hemoglobin dissociation curve is entirely independent of respiratory rate or minute volume. Again, avleolar diffusing capacity is also independent of respiratory rate or minute volume.

Clear?

SLR - thanks for the math. I'm still a bit confused, though:

The way I've been taught, forced hyperventilation is a good technique because one of the main issues at altitude is that your body's auto-regulating systems break down. Specifcally, the CO2 transfers from the blood to the atmosphere easily, but O2 doesn't make it into the blood as well. Since the body relies on CO2 content in the blood for regulating breathing, you don't breathe as heavily as you need to in order to get enough O2.

This makes intuitive sense - your equations seem to imply that the aveoli are bathed in the atmosphere. But as a breath is held, doesn't FiO2 drop as O2 migrates to the blood?

Dunno if anyone has already posted this, can't be arsed to read it all right now!

I read somewhere (though it was a theory more than anything, no research had been done on it) that giving blood may help with acclimitisation. Giving blood shortly before you go would make you slightly hypoxic, basically simulating altitude. I have no idea whether this would work, and if it did how useful it would be, but I think there's a case for research there.

Sierra Ledge Rat wrote:Hyperventilation has absolutely nothing to do with the transfer oxygen from lungs to blood.

And don't even try to argue that R


Clear?

I don't know what's with the attitude, but it makes it tough to respond without some attitude as well, since you are simply wrong.

Here's a little writeup to save space (and might as well document anyways)

Basically, you are just staring at an equation as if it's static. Except the part you tossed to the side about PCO2 - actually yeah hyperventilation does have a significant effect on reducing it.

Haven't you read anything? People hyperventilate at altitude, there is a reason.

Some people who LIVE at altitude chronically hyperventilate.

There's plenty of evidence that it has an effect.

Clear?

my blog is simply restating what has been stated elsewhere. I am not 'creating knowledge'.

If you want to argue against it, I am all for it. I am going off of information such as provided in from a respiratory physiology textbook.

Hyperventilation

The most important feature of acclimatization to high altitude is hyperventilation. Its physiological value can be seen by considering the alveolar gas equation for a climber on the summit of Mount Everest. If the climber's alveolar PCO2 were 40 and respiratory exchange ratio 1, the climber's alveolar PO2 would be 43 - (40/1) = 3 mm Hg! However, by increasing the climber's ventilation fivefold, and thus reducing the climber's PCO2 to 8 mm Hg (see p. 16), the climber can raise his or her alveolar PO2 to 43 - 8 = 35 mm Hg. Typically, the arterial PCO2 in permanent residents at 4600 m (15,000 ft) is about 33 mm Hg.

So if you want to say I'm spreading wrong information, then you will agree that a respiratory physiology textbook (and www.altitude.org) are as well. And perhaps you are right

and to the OP's question, I was simply speculating that perhaps if you 'practice' hyperventilating before going to high altitude, you'll be able to reduce some of the side effects related to hyperventilation. Because you will hyperventilate at altitude.

FortMental wrote:It wouldn't be the first time that a textbook is wrong, or at the very least, inaccurate. Even Smith and Dempsey flub it in their paper, "Control of Breathing at High Altitude". Using the term "hyperventilation" to describe any-and-all involuntary increases in breathing rate is simply incorrect. You and your textbook are just being sloppy. Personally, I don't really give a shit.... I just like to make sure that when we talk, the words mean the same thing to everyone.

Fine by me. I've been just going on what I've been reading out there. So would you simply prefer to call it increased ventilation response?

here is some other physiologist's take on altitude response

he calls the response "hypoxic ventilatory response".

in the end, the same concept applies, increased ventilatory response increases ability to get oxygen into the blood.

Ze's basically arguing that by hyperventilating and reducing pCO2 you can drive up the A-a gradient, which is what I argued against. The math shows that this effect is tiny.

Anyway I don't think we have that much control over our own minute volume. I mean, we basically breath as fast and as much as our brain stem demands. You can try to over-ride with your cerebral cortex, but as soon as your attention wanders you're back to brain stem control.

You're either born with genetics that allows you to perform at altitude, or you're not.

I briefly reviewed the other data posted by Ze and it's pretty good.