In my personal medical Himalayan researches, the blood test to study the parameters of hematocritum is one of the most interesting I am meisuring.
When our body is exposed to high altitude levels, we need a few days to be aclimatized to the hipoxia caused by low atmospheric pressure.
Our body responses to this hipoxia by different ways, such as cardiopulmonar or metabolic adaptation, but one of the most important ways is the hematological response.
When our body feels the hipoxia, it begins to increase hemoglobin levels by EPO hormon activation. It means that, in a few days to some weeks, we will have more oxigen-transporters cells. Blood will be more dense, and that has its own risks, but we need it to get a good performance at this altitude. We can meisure this by blood tests, and nowadays there are different posibilities, as EPOC READER analizer, commercialized by ALERE laboratories, that let me carry one sample to the Himalayas.
After many expeditions meisuring blood tests, in which I can check hemoglobin, hematocritum, pH and electrolites, I have been able to see different speeds in getting higher hemoglobin levels in my team members, and differences between sherpas and us.
Normally, our hematocritum varies between 42-46% for men and 40-44% for women in health. It can be higher in smokers, some hematological sickness and cronical exposure to high altitude level.
The most of us can reach 54-57% after three to four weeks exposed to hipoxia due to high altitude ; only old persons will increase less, until 52% as maximum (their normal hematocritum is 38-41%). There are differences in aclimatizing speed, but normally all of us will reach the same value.
Higher levels can be dangerous, because there is a high risk of trombosis due to dehidratation and poliglobulia, and I have only meisured them after summit push or bivouacs too long upper than 7500 mt.
At base camp lower than 4500 mt, too long days staying at this altitude , without feeling the hipoxia’s stimule, can make hematocritum to decrease softly. But if we continue being exposed to hipoxia when we climb up to higher camps, by a short term stay, this stimule will increase a bit our levels during next days, although we are resting at base camp. That is the reason why we need to climb up continously, not only to equip or prepare the mountain, but also to continue looking for the hipoxia stimule of extreme altitude.
On the other hand, I have studied some differences between caucassians and sherpas.
Sherpas don’t need to increase their red cell levels because their hemoglobin is adapted to high altitude, so it can transport more oxigen molecules than our red cells. They don’t need to get aclimatized to the base camp altitude, only for extreme altitude, starting from 6500 meters. Only by equiping camp 3, 4 and during summit push their levels will be increased!!!
To resume… the increase of hemoglobin, red cells or hematocritum levels due to high altitude hipoxia is necessary to have a good performance in these ambiental conditions, although it can be dangerous for alpinists due to a higher risk of trombotic events (including cardiac stroke, TEP or brain stroke), or worst consecuences in case of frostbites.
Sherpas can feel this sickness, but they have less posibilities because they are genetically adapted to high altitude hipoxia.