Lesson 4: Pressure in lungs

In 4.1, dr. Ainslie mentions that lungs in high altitude become more pressurized (around 1:55), does it mean that the blood pressure in the lungs is higher? And if so, does higher blood pressure also inhibit the diffusion of oxygen into blood?

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Here is link to a summary of measurements of BP at Mt. Everest basecamp (5400m): Everest Study Finds High Altitude Affects Blood Pressure – WebMD

There are quite a few factors that can influence the movement of oxygen into blood (and binding to hemoglobin), including heart rate, ventilation rate/volumes, etc, but fundamentally the concentration gradient is what determines the efficiency of gas exchange during respiration.

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Thank you @DavidHik! So if I understand it correctly, it is the oxygen deprivation that causes the rise in BP, which can also happen to people with chronic conditions causing lower levels of oxygen. Interesting!

Hi @jirim - yes this seems to be the case. I am not a medic, but you are not the first to ask about this and I have done a bit of asking around. There are a bunch of papers that seem to involve taking Danish ‘lowlanders’ to high places and monitoring their physiological responses. I guess perhaps all Danes are ‘lowlanders’ by definition! Anyhow, here is a link to one paper that I think elaborates in quite more detail about the question you were asking - " Chronic hypoxia increases blood pressure and noradrenaline spillover in healthy humans": Chronic hypoxia increases blood pressure and noradrenaline spillover in healthy humans

“In summary, this study shows that chronic hypoxia causes marked activation of the sympathetic nervous system in healthy humans and increased systemic arterial pressure, despite normalisation of the arterial O2 content with acclimatisation.”

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@jirim - this has very little to do with mountains or your original question but I was just reading about a tangentially related problem that I have been curious about: do giraffes have issues with high blood pressure because their heads are so far from their heart?

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Interesting, so it seems that despite the acclimatization, and improved blood O2 levels, the sympathetic, i.e. “fight and flight”, reaction of the body remains as well as the elevated blood pressure.

Thanks for the reference @DavidHik !

I also got an answer from dr. Ainslie himself (I really admire the “meet the instructors” aspect of this course), in which he pointed to me that raised BP is ok to a certain extent, since it helps the non-ventilated parts of lungs to become better perfused with blood and oxygen. Nevertheless, the extreme levels of BP in lungs lead to HEPA, which can be lethal.

Moreover, thanks for the great article about giraffes, it has never occurred to me that this might be a problem, but it makes sense. Since many people have problems getting up too quickly (I have a friend who loses her vision for a brief moment after getting up too hastily), how is it possible that when a giraffe moves its head along a several meters long vertical path it’s ok. Fascinating!

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