05 October 2021

The Dalai Lama's perilous escape from Tibet


It's a story that I remember hearing years ago, but the details of which I had never seen until reading an article in the August 2019 National Geographic.  In 1959 Tibetans feared that the Dalai Lama would be seized by the People's Liberation Army of China, so they engineered his escape from Tibet to India.  The escape route entailed traveling upward from Lhasa, over passes at 15,000 feet altitude, then 16,000 x4, then 17,000 feet (5200 meters), over a period of two weeks, then gradually down to sea level in India, as indicated on the embedded graphics.


The magazine apologizes for using "variable scale" in the images, and I normally decry deceptive y-axes on graphs, but in this case I'll give them a pass because of the enormous problems in graphing Himalayan peaks to scale.  What impresses me now is the awesome altitudes traversed, even granting that the participants had a lifetime's adaptation in terms of their heart, lungs and hemoglobin.  

11 comments:

  1. The link in the article goes to National Geographic's main page. I searched for the article (searched "Dalai Lama Tibet," "August 2019"). I could not locate the article. Do you possibly have a direct link? Google gives me lots of articles about the escape from Tibet, but no Nat Geo article.

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    1. National Geographic jealously guards its content, sharing only a small portion online. I scanned the images from my hard copy of the magazine. Your local library will almost certainly have copies available for reading.

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  2. There's roughly half the available oxygen at 17,000 feet as at sea level. The human body is pretty amazing.

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    1. At the risk of sounding offensively technical, there is actually the same amount of oxygen available at 17,000 feet (or at the top of Mount Everest) because our atmosphere is 20.9% oxygen all the way up.

      The difference is in the atmospheric pressure, which is much lower and isn't capable of driving that oxygen across cell membranes into the blood as well as it does at sea level.

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    2. I'm sorry, but less pressure means less molecules and hence less oxygen. The percentage (or partial pressure in scientific terms) remains the same, but the total amount of molecules or substance goes down at lower pressure.

      I don't think that it is the outside pressure that drives oxygen into your cell membranes either, but I'm not a biologist or lung surgeon so I'm gonna have to let the explanation of the exact mechanism to others.

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    3. Nepkarel, I may be wrong about the "amount" of oxygen molecules per liter at altitude. But I am confident re the percentage and the role of atmospheric pressure in driving diffusion.

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    4. We agree on the percentage. That doesn't change.

      But think of a balloon full of air at sea level. If you bring it up to high mountains, it will expand because of the lower pressure. So the same amount of air will take up more space, and therefore have less "air" per volume. However, the composition of the air in the balloon will remain the same. Still 80% nitrogen, 19% oxygen and 1% other stuff. However, when breathing this lower pressure air, you get less oxygen in your lungs per breath of air. That is what causes the shortness of breath.

      BTW, the same happens the other way when you increase pressure, for instance when you go SCUBA diving. Pressure goes up fast. Every 10m/30ft you get an extra bar of pressure. All SCUBA divers know to NEVER hold their breath because should they unexpectedly ascend, their lungs would burst from the expanding air in their lungs. And that's aside from any bubbling from the extra dissolve air in their blood, aka the bends.

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  3. That's why I said available. But I'm sure you, being in the pulmonary field, know much more about it than I.

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    1. I know you understand this; I'm just making the point to clarify for others who might log on to this discussion thread. I think the best way to phrase it would be to say that at these extreme altitudes there is less oxygen available in the blood (though not in the air).

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  4. For comparison, the ski resort towns of Colorado are around 8,000 feet, if you've ever tried to walk uphill in those places.

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  5. Just because China's annexation of Tibet was largely bloodless doesn't mean it was okay. I've heard of the Dalai Lama all my life without anyone pointing out what China did.

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