Breathing in the mountains, and under water

The higher one ascends the mountains or higher than his plane, the more sparse becomes the air. At the height of 5.5 km above sea level atmospheric pressure is reduced almost by half; in the same way and reduced oxygen content. Already at the height of 4 km untrained person can get sick of the so-called mountain sickness. However, by training you can train the body to stay and at higher altitudes. Even when climbing MT heroes-climbers did not use oxygen devices. How the body adapts to the poor oxygen in the air?
The main role here is played by the increase in the number of red blood cells, and hence increase the amount of hemoglobin in the blood. The inhabitants of mountain regions the number of erythrocytes reaches 6 million or more in 1 mm3 (instead of 4 million in normal conditions). It is clear that this blood gets the opportunity to capture more oxygen from the air.
By the way, sometimes people, who had been in Kislovodsk, include the increase of hemoglobin in their blood due to the fact that they are well rested and recovered. Of course, it is not only this, but just in the influence of the mountain area.
Divers and those who work in caissons - special chambers used in the construction of bridges and other hydraulic structures have, on the contrary, to work at high pressure air. At a depth of 50 meters under water diver feels the pressure is almost 5 times higher than the atmospheric one, and he sometimes have to go down under the water to 100 m and more.
Air pressure effect is very peculiar. People working in these conditions for hours without feeling from increased pressure no trouble. However, a quick rise to the top appear acute pain in the joints, skin itching, vomiting; in the most severe cases, there were deaths. Why is this happening?
In everyday life we do not always think the force is pressing on us air. Meanwhile, the pressure is very big and is about 1 kg per square centimeter of the surface of the body. The last man of medium height and weight equal to 1.7 m2. In the end, the atmosphere puts pressure on us with the power to 17 tons! We do not feel this huge pressure-impact because it is balanced by the pressure of body fluids and dissolved gases. Fluctuations of atmospheric pressure causes some shifts in the body, which is especially noticeable patients with hypertension and diseases of the joints. Because when changing atmospheric pressure at 25 mm RT. senior force of atmospheric pressure on the body is changing more than a ton! The body must balance this shift pressure.
However, as already mentioned, stay under pressure even in 10 atmospheres relatively well tolerated by the diver. Why is rapid rise can be deadly? The thing is that in the blood, as well as in any other liquid at high pressure and related gases (air), these gases are dissolved more significantly. Of 4/s air nitrogen, completely indifferent for an organism (when it is in the form of free gas), large quantities of dissolved in the blood of the diver. If the air pressure is declining rapidly, gas begins to come out of solution, blood boils", highlighting the bubbles of nitrogen. Bubbles these are formed in the blood vessels and may clog a vital artery in the heart, brain, etc., So divers and working caissons very slowly raise to the surface so that the gas was allocated from the pulmonary capillaries.
No matter how different effects stay high above sea level and deep under water, there is one link them a link. If people very quickly rises to the plane in rarefied atmosphere, above 19 km above sea level need complete sealing. At this altitude pressure reduced so that the water (and became to be, and the blood boils already not at 100 C and at body temperature. There may be events decompression sickness in their origin similar decompression sickness.