Altitude sickness, Part 1

How do you prepare for the rigorous physical requirements of high elevation adventure? Strength and endurance are key, but are only part of a more complex equation. How do you prepare for changes in altitude, exposure, diet, etc.? How do you mentally prepare? Learn from others and share what you know about training in advance for outdoor adventures.
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gregw822
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Altitude sickness, Part 1

Post by gregw822 » Wed Apr 07, 2021 11:17 am

Since it's slow around here, and since someone posted something about altitude sickness and Diamox last week, I thought I would offer this.

Altitude sickness has a lot to do with the acid/base properties of blood. The chemistry scale for acid/base solutions is a function called "pH". A neutral solution, neither acidic nor basic, has a pH of 7.00. An acidic solution has a pH of less the 7.00, and a basic solution has a pH greater than 7.00. The scale is logarithmic, so pH 9.00 is ten times more basic the pH = 8.00. A solution with a pH of 4.00 is ten times more acidic than pH 5.00 and one hundred times less acidic than pH = 2.00.

Human blood has a pH of 7.40, very slightly basic, and is very intolerant of changes in that value. Changes in blood pH by only a few tenths of a unit can cause severe illness or death. Metabolic processes generate waste byproducts that are acidic, and the most important of these is carbon dioxide, CO2. You might be surprised to learn that CO2 is an acid, but in water (i.e. blood), carbon dioxide produces a small amount of carbonic acid, like this:

CO2 + H20 ⇄ H2CO3 ⇄ H3O+ + HCO3-

The double arrows mean the reaction runs both directions, continuously, but the relative amounts of each chemical species do not change in value if the system is in the stable state of "chemical equilibrium". Chemical equilibrium means the specified reactions run in both directions at the same time and the same rate, so there is no net change in the system over time.

CO2 produced by metabolism is transported from tissue through the blood to the lungs for exhalation. In the absence of a regulatory mechanism, dissolved CO2 is acidic enough to drop the pH of blood to about 5.6, a value that would result in rapid death. The condition of acidosis results from a blood pH that drops below normal limits. Acidosis can result from diabetes, kidney failure or persistent diarrhea. Temporary acidosis can result from prolonged vigorous exercise, via excess CO2 produced by amped up metabolism. The opposite condition, alkalosis, results from blood pH higher than the normal range. Alkalosis can result from hyperventilation or severe vomiting.

Fortunately, the blood does have a regulatory mechanism for holding a constant pH. It's a complex system, but much of it involves the CO2/H2O chemistry shown in the equation above. In chemistry terms, we say the blood is "buffered" against pH changes. (Anyone who has taken a year of college general chemistry will have given an involuntary shudder upon reading the word "buffer". 😀)
This will do for an introduction. if the topic is relevant and of interest, I will continue in Part 2 with how this applies to altitude sickness and about what Diamox does to prevent the condition.
Last edited by gregw822 on Sat Apr 10, 2021 1:24 pm, edited 2 times in total.








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c9h13no3
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Re: Altitude sickness, Part 1

Post by c9h13no3 » Wed Apr 07, 2021 1:09 pm

Wat, dis a hiking forum.

I just wanna see you invoke the Henderson Hasselbalch equation.
"Adventure is just bad planning." - Roald Amundsen
Also, I have a blog no one reads. Please do not click here.

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gregw822
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Re: Altitude sickness, Part 1

Post by gregw822 » Wed Apr 07, 2021 1:20 pm

I could do that, and I can derive it. But none of us wants that. And your molecule is one of my favorites.
Don't see how altitude sickness isn't relevant to hiking, but whatever.....

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Re: Altitude sickness, Part 1

Post by sekihiker » Wed Apr 07, 2021 2:26 pm

I'm looking forward to Part 2. Your explanation has been very well done.
As far as I can remember, I have never suffered from altitude sickness that wasn't cured by slowing down and spending a day or so at altitude.
My wife, on the other hand, has major problems with it.

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Re: Altitude sickness, Part 1

Post by bobby49 » Wed Apr 07, 2021 7:54 pm

Starting out the discussion about blood pH probably got you off on the wrong foot with certain oldtimers. About fifty years ago, Larry Penberthy (Mister MSR) started ranting about blood pH, and he had everybody piss on some pH test papers when they were halfway up Mount Rainier. He had a theory, but lots of people complained about his methods. I believe that he was eventually chased out, even though there are fragments of scientific truth.

Personally, I've been up to almost 7000 meters without altitude sickness. Typically on some of the big peak expeditions, I am the only one who didn't get sick from anything.

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Re: Altitude sickness, Part 1

Post by Jim F » Wed Apr 07, 2021 10:10 pm

I would suggest changing "Human blood has a pH of 7.04" to "Human blood has a pH of 7.40." Call for the Crash Cart if you encounter an unfortunate individual with a pH of 7.04.

Jim

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Re: Altitude sickness, Part 1

Post by gregw822 » Thu Apr 08, 2021 7:46 am

Good grief. Fixed. Nice catch. I swear, whatever I write, no matter how many times I read for edits, there is always at least one typoe. It's very frustrating. Thanks.

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Re: Altitude sickness, Part 1

Post by oldranger » Thu Apr 08, 2021 8:43 am

sekihiker wrote:
Wed Apr 07, 2021 2:26 pm
I'm looking forward to Part 2. Your explanation has been very well done.
As far as I can remember, I have never suffered from altitude sickness that wasn't cured by slowing down and spending a day or so at altitude.
My wife, on the other hand, has major problems with it.
Similar here. One night at 7500 plus and I am good to go. My wife, on the other hand, needs a night at 6000 then a couple more at 8,000 before she can handle more. And that is with our base altitude of 3600 ft.
Mike

Who can't do everything he used to and what he can do takes a hell of a lot longer!

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Jason
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Re: Altitude sickness, Part 1

Post by Jason » Thu Apr 08, 2021 8:43 am

Do Part 2!!!! I'm invested now and want to see how the story continues!

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Re: Altitude sickness, Part 1

Post by gregw822 » Thu Apr 08, 2021 9:06 am

Thanks for the enthusiasm. I'll work on it later today.

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