High altitude weight loss clinic

[Attitude]

A High Altitude

[fern]

I'm with Dru ... i think I read somewhere that the

scientific explanation for the altitude/latitude thing

was bunk. But from what I've been told it's subjectively

true that a given altitude is 'harder' at high latitudes

than low. Eg, I was told 5000m on Mt Logan feels like

6000m in the Cordillera Blanca. My guess is that the

extra cold and dryness and remoteness play a role. Also I

would bet that some of this 15% body mass loss on short

expeditions involves a lot of water loss, not fat or muscle.

[ryland_moore]

Check out these sources:

http://www.cc.utah.edu/~sa11170/Part%202/4altmed.html

 

http://www.storysmith.net/Articles/Altitude.pdf

 

The second is a good read!

[Dru]

Second one seems kinda suspicious in a few places like where they claim the Death zone is 5500m, and that above that you cannot acclimatize - with no references.

 

and again, in the first one

 

"Variables affecting Pb

 

Latitude

- Pb decreases the further we get from the equator

- so, if we increase latitude we decrease Pb

ex: Mount Everest is located about 27° N latitude and at the summit has a Pb of 250mmHg. Mount McKinley however, is located at about 62° N. If the summit of Mount McKinley was the same [i think there should be a word "elevation" here] as that of Everest, McKinley's Pb would be about 220mmHg

Season

- Pb is typically lower during the winter that during the summer"

 

No references

Also the last sentence is bunk, cold air = higher pressure = higher Pb so why would it be "lower in the winter"

 

[snoboy]

Dru said:

- Pb is typically lower during the winter that during the summer"

 

No references

Also the last sentence is bunk, cold air = higher pressure = higher Pb so why would it be "lower in the winter"

 

Are you sure that cold air= high pressure? Or do we just associate those two because of the weather systems we normally get here?

Most of our cold spells are due to high pressure systems. Recently though we had one where there was a massive low parked further inland than usual, and it was pulling cold air down the "back" of it.

[fern]

click

 

this one has some numbers. Still, I don't see how you can make them tell you

that the effect is equivalent to a 4000' disparity. My envelope-back number

crunching says maybe 1100' is reasonable, considering the Himalaya is

not equatorial and Denali is not polar.

[Dru]

well cold and low are relative, but colder air is denser, therefor heavier, therefore higher pressure. Of course, denser air sinks, so at some level a high pressure on the ground is equal top a low pressure aloft, but we're talking relative, right... in At Sci we used the 500MB level as the mid elevation...when you have an 8000m mountain poking up it tends to be a high "ground level' and you dont get the same amount of sink you do over an 8000m column of air with bottom at sea level, which is why when a high pressure system hits in the mountains, your barometer goes up (apparent elevation drops) even at high elevation.

 

weather

[catbirdseat]

Part of it makes sense but not all of it.

ryland_moore said:

As for bug's question, I have lost weight on Aconcagua where you spend more time above 16k than below, but on Orizaba, this is not the case, as you go from 14 k to the summit typically.. An expedition climb you could expect to lose weight (mass). Whether that translates into fat cells, I don't know. I do not have much fat cells (i think) and I still lost ~15lbs. of mass (muscle and fat?) anyways, it came right back on after a few days of eating and celebrating!

 

As for Dru's question: I have heard this is a bogus statistic

 

Can anyone comment?

 

I had it expalined to me by a doctor who is steeped in altitude related illness and this is generally what he told me:

 

There are roughly the same amount of oxygen molecules at 20k as at sea level, but due to profusion pressure, your body can not readily absorb the oxygen, hence the feeling of receiving less Oxygen into the blood stream as you go higher in elevation.

This is not entirely accurate. When atmospheric pressure drops, the partial pressure of oxygen drops accordingly. The partial pressure of oxygen is 0.21 times the amospheric pressure. At 16k ft this would be 0.21 x 0.5 atm=0.1 atm O2. The concentration of oxygen in your blood must be maintained by your body at a constant level regardless of the partial pressure in your lungs. At altitude, you breath in fewer molecules of O2 with each breath (and transfer to blood is less efficient too), and hence you must take more breaths in a given amount of time to saturate the hemoglobin in your blood.

 

He explained that the weight of air above you pushes the Oxygen molecules into the blood stream, absorbed in the lungs. The less pressure (ie. the higher in elevation you are b/c of less weight above you), the harder it is to take in O2 into the lungs. As you go up in elevation there is less pressure (less atmosphere pushing down on the body (similar to diving with atmospheres but air weighs less, so it takes considerable more air mass to notice a difference, whereas in water an atmosphere is every 33 ft.)

Yes. The pressure increases by 1 atm for every 33 ft of water, or decreases by half for every 16,000 ft of altitude.

 

So, the shape of the Earth also dictates the thickness of the atmosphere. The atmosphere is thickest at the equator and thinner at the poles. So, at 20k at the equator, there is more atmosphere above you than at 20k on Denali hence less profusion pressure on a climber at 20k on Denali than at 20k in the Himalayas or N. Andes, hence the feeling of Denali feeling like a "24k ft mountain in the Himalayas" (ie. the amount of air (hence pressure) on a climber at 20k on Denali is equivelent to the amount of air/pressure on a climber at 24k in the Himalayas or near the equator.

Earth's rotation accounts for its distorted shape. The centripetal force causes the earth to bulge. The atmosphere bulges proportional to the rest of the globe. I know that storms can rise to 40k ft at the equator, but the cloud tops seldom exceed 20,000 ft in the actic, but this may have more to do with temperature than pressure. The Nova website on Everest puts the pressure at the summit 3,000 ft lower than it would be if it were at the same latitude as Denali. Some of this extra pressure comes not from the latitude effect but because Everest is located at the center of a continental land mass, whereas Denali is at the margin of one. High pressure systems center on big land masses with highest pressure towards the center of the continent.

The doctor could have been bullshitting me, but he seems credible. He studied altitude for his dissertation and has been a climber for 25 years. Anyone have anything to add. Did my rambling make any sense?

Couldn't be Tom Hornbein. He's been climbing for a lot longer than that. Edited March 25, 2003 by catbirdseat

[Dru]

The atmosphere bulges proportional to the rest of the globe.

 

Are you sure about this, its the one I thought was different, but I can't remember correctly. I do remember reading a science fiction novel about a planet with exaggerated axial flattening such that each pole bulged entirely out of the atmosphere, which (for some physics lesson reason) stayed spherical. And that's opposite to what you suggest.

 

Also, the concentration of O2 in air (hence Ppressure) does change slightly with elevation, (for the same reason we find very minimal amount of hydrogen at the surface, ie gravitational separation, but compounded by turbulence so it neverstratifies...) but its effect on physiology is minimal at human-operable elevations so it is usually discounted in altitude med. discussions.

[fern]

cbs said:

The atmosphere bulges proportional to the rest of the globe.

 

I quote from my own link above:

 

A commonly mistaken explanation of pressure altitude is that it is the result of the centrifugal forces of the Earth's spin that draws the atmosphere toward the equator to form an equatorial bulge.

 

"The equatorial bulge is a result of centrifugal forces and represents the Earth's physical shape, not that of the atmosphere", Parish said.

 

"Our atmosphere is thermally driven, not mechanically driven" ,said Parish.

 

 

 

[Dru]

oh the fulfillment of actually remembering something correctly from at. sci nerd hood!

[fern]

sure - but I think PV=nRT refutes what you are saying about cold air = high pressure.

[Winter]

fern said:

cbs said:

The atmosphere bulges proportional to the rest of the globe.

 

I quote from my own link above:

 

A commonly mistaken explanation of pressure altitude is that it is the result of the centrifugal forces of the Earth's spin that draws the atmosphere toward the equator to form an equatorial bulge.

 

"The equatorial bulge is a result of centrifugal forces and represents the Earth's physical shape, not that of the atmosphere", Parish said.

 

"Our atmosphere is thermally driven, not mechanically driven" ,said Parish.

 

 

 

If there's no difference in the "depth" of the atmosphere as you move from north to south than this whole theory is out the window. How else can you explain a difference in "apparent" altitude from one latitude to the next?

 

[Winter]

fern said:

sure - but I think PV=nRT refutes what you are saying about cold air = high pressure.

 

Yeah I thought I was taught in high school physics that temperature and pressure are directly proportional.

[Winter]

Ok now I get it after reading fern's link. I was trying to conceptualize all of this in a vacuum assuming temperature and weather conditions were a constant at both latitudes. In reality, though, the perceived difference results from lower relative temperatures at the poles, which results in lower relative air pressure or density.

[Norman_Clyde]

Air pressure and temperature are not necessarily related. you will realize this intuitively if you think of pressure relating to 1) the total number of air molecules per unit volume and 2) the average energy of each molecule. Temperature relates to the average energy. The number of air molecules per unit volume will determine the density, and will affect the pressure only if the density changes while the energy of each molecule remains constant. If you pressurize air that is at a constant temperature, as with a bicycle pump, it will heat up. But if an air mass cools without any restrictions on its ability to contract (i.e. an open system like the atmosphere), it will become more dense without necessarily changing in pressure. Very cold air at sea level is very dense-- the reason why sound travels so well in cold air, and planes can take off with less runway when it's cold. But the cold air has less energy per molecule, so it is not higher pressure even though it's more dense. I've always understood the transfer of oxygen into the blood to relate to partial pressure of oxygen, so to breathe cold dense air does not put more oxygen into your blood if the air pressure does not change.

 

I've read in several places that the atmosphere is thinner at the poles, and I understood it to be due to the effect of the earth's rotation. Apparently the air pressure at the south pole, which is only a few thousand feet above sea level, is the same as at 10,000 feet at the equator. I just tried looking it up in my astronomy book to find the answer, but had no luck.

[Dru]

just trust me on this, dry cold air = sinking = high pressure. warm moist air = rising = low pressure. i will have to drive to west van to get my textbook though, if you need a reference.

 

you just have to remember warm and cold are relative. for instance, the subtropical high that keeps the deserts arid is pretty warm to us northerners, but its still cold relative to the warm, moist air over the tropical rain forests in the heighbouring low.

[AlpineK]

Dru said:

just trust me on this, dry cold air = sinking = high pressure. warm moist air = rising = low pressure. i will have to drive to west van to get my textbook though, if you need a reference.

 

you just have to remember warm and cold are relative. for instance, the subtropical high that keeps the deserts arid is pretty warm to us northerners, but its still cold relative to the warm, moist air over the tropical rain forests in the heighbouring low.

 

I've been kicking myself for selling my meteorology textbook.

 

Dru is right. Tropical air is warm and moist due to the high angle of incidence of the sun. There are no deserts in the tropical latitudes.

 

Temperate air is cooler and the atmosphere is less thick. There are 2 statistical high presure areas over the atlantic and pacific in the northern hemispere. Land masses to the east of the high presure areas are desert.

 

Both poles, due to low temps have sinking air and thus high presure. Both the artic and antartic are very dry.

 

 

[JayB]

Figger_Eight said:

Ryland, your doctor was right.

 

Oxygen gets transported into your bloodstream as a result of the pressure gradients between the atmosphere and your bloodstream. As the pressure in the air decreases, the "push" of oxygen into the bloodstream decreases. The percentage of oxygen in the air at upper elevations is the same as sea level, but the pressure is less.

 

Yup. The partial pressure of O2 is the key.

 

 

Fat cells in which the fat vacuole has been entirely exhausted aren't going to make someone a whole lot heavier than fat cells which have ceased to exist altogether, two fat cells with X/2 units of fat in them will not make you any fatter than 1 fat cell containing X units of fat, etc, so I'd be less worried about controlling the number of fat cells in my body and more worried about the quantity of fat in the said cells. Spending three weeks with a pack on your back in the mountains should take care of that as well as anything, short of a month-long hunger-strike in a sauna, though.

[Attitude]

Bug said:

Does anyone know a good reference on the effects of altitude on physiology?

I believe the reference book on the topic is "High Altitude Medicine and Physiology " by Ward, Milledge, and West. I have the 3rd Edition (2000) sitting in front of me.

 

They say:

 

The barometric pressure at the Earth's surface and at 24 km is essentially independent of latitude. However, in the range of about 6-16 km, there is a pronounced bulge in the barometric pressure near the equator in winter and summer.

 

Therefore, Everest at 6 km has more oxygen than Denali at 6 km. They say the cause is a very large mass of very cold air in the stratosphere above the equator.

[Bug]

Attitude said:

Bug said:

Does anyone know a good reference on the effects of altitude on physiology?

I believe the reference book on the topic is "High Altitude Medicine and Physiology" by Ward, Milledge, and West. I have the 3rd Edition (2000) sitting in front of me.

 

They say:

 

The barometric pressure at the Earth's surface and at 24 km is essentially independent of latitude. However, in the range of about 6-16 km, there is a pronounced bulge in the barometric pressure near the equator in winter and summer.

 

Therefore, Everest at 6 km has more oxygen than Denali at 6 km. They say the cause is a very large mass of very cold air in the stratosphere above the equator.

Cool. I'll go get it. See you all when I'm skinny. Maybe.

[Winter]

The one other variable is that the Earth bulges at the equator so there is more gravity or the force of gravity is greater.

 

 

[Dru]

Winter said:

The one other variable is that the Earth bulges at the equator so there is more gravity or the force of gravity is greater.

 

 

hmm, if you are further away from the center of gravity, then gravity should be lower, not higher. F= -G M1 M2/R^2, and you have a higher R.

[ryland_moore]

Well, you guys are over my head cracking out phydics equations, although I vaguely remember PV=nRT! Anyways, I will find out how "I" feel at elevation on Denali and compare it to how I remember feeling on Chimborazo and Aconcagua, although a lot more comes into play like how I am training now! Really interesting topic though.

 

Also, someone I think made a comment about there being no deserts in the tropics. This is not true. They may not be enormous deserts, but they are classified as desert areas by the annual amount of precipitation received: Look at the NW coast of Costa Rica, the Islands off the coast of Venezuala (Bonaire) and N. Chile (not sure if that is tropics or temperate). Not all areas in the tropics are lush and green!

[Winter]

Dru said:

Winter said:

The one other variable is that the Earth bulges at the equator so there is more gravity or the force of gravity is greater.

 

 

hmm, if you are further away from the center of gravity, then gravity should be lower, not higher. F= -G M1 M2/R^2, and you have a higher R.

 

It could work that way too ... what the hell do I know?