Acclimatization

During a long stay at altitude, a number of changes occur in the body, the essence of which boils down to maintaining normal human functioning. This process is called acclimatization. Acclimatization is the sum of adaptive-compensatory reactions of the body, as a result of which good general condition is maintained, weight constancy, normal performance and the normal course of psychological processes are maintained. A distinction is made between complete and incomplete, or partial, acclimatization.

Due to the relatively short period of stay in the mountains, mountain tourists and climbers are characterized by partial acclimatization and adaptation—short-term (as opposed to final or long-term) adaptation of the body to new climatic conditions.

In the process of adapting to the lack of oxygen in the body, the following changes occur:

— since the cerebral cortex is extremely sensitive to oxygen deficiency, the body in high altitude conditions primarily strives to maintain proper oxygen supply to the central nervous system by reducing the oxygen supply to other, less important organs;

-The respiratory system is also highly sensitive to lack of oxygen. The respiratory organs respond to a lack of oxygen by first breathing deeper (increasing its volume):

Table 2

and then by increasing the respiratory rate:

Table 3

As a result of some reactions caused by oxygen deficiency, not only the number of erythrocytes (red blood cells containing hemoglobin) in the blood increases, but also the amount of hemoglobin itself (Fig. 4). All this causes an increase in the oxygen capacity of the blood, that is, the ability of the blood to carry oxygen to the tissues increases and thus supply the tissues with the necessary amount. It should be noted that the increase in the number of red blood cells and the percentage of hemoglobin is more pronounced if the ascent is accompanied by intense muscle load, that is, if the adaptation process is active. The degree and rate of growth in the number of red blood cells and hemoglobin content also depend on the geographical features of certain mountainous areas.

The total amount of circulating blood also increases in the mountains. However, the load on the heart does not increase, since at the same time the capillaries expand, their number and length increase.

In the first days of a person’s stay in high altitude conditions (especially in poorly trained people), the minute volume of the heart increases and the pulse increases. Thus, for physically poorly prepared mountain climbers, at an altitude of 4500 m, the pulse increases by an average of 15, and at an altitude of 5500 m, by 20 beats per minute.

At the end of the acclimatization process at altitudes up to 5500 m, all these parameters are reduced to normal values ​​​​characteristic of normal activities at low altitudes. Normal performance is also restoredgastrointestinal tract. However, at high altitudes (over 6000 m), the pulse, breathing, and work of the cardiovascular system never decrease to normal values, because here some human organs and systems are constantly under conditions of a certain tension. Thus, even during sleep at altitudes of 6500–6800 m, the pulse rate is about 100 beats per minute.

It is quite obvious that for each person the period of incomplete (partial) acclimatization has a different duration. It occurs much faster and with fewer functional deviations in physically healthy people aged 24 to 40 years. But in any case, a 14-day stay in the mountains under conditions of active acclimatization is sufficient for a normal body to adapt to new climatic conditions.

To eliminate the possibility of serious mountain sickness, as well as to shorten the acclimatization time, we can recommend the following set of measures, carried out both before leaving for the mountains and during the trip.

Before a long high-altitude journey, including passes above 5000 m in the route, all candidates must be subjected to a special medical and physiological examination. Persons who cannot tolerate oxygen deficiency, who are physically insufficiently prepared, and who have suffered from pneumonia, sore throat or serious flu during the pre-trip preparation period should not be allowed to participate in such hikes.

The period of partial acclimatization can be shortened if the participants of the upcoming trip begin regular general physical training in advance, several months before going to the mountains, especially to increase the body’s endurance: long-distance running, swimming, underwater sports, skating and skiing. During such training, a temporary lack of oxygen occurs in the body, which is higher, the greater the intensity and duration of the load. Since the body here works in conditions somewhat similar in terms of oxygen deficiency to being at altitude, a person develops an increased resistance of the body to a lack of oxygen when performing muscular work. In the future, in mountainous conditions, this will facilitate adaptation to altitude, speed up the adaptation process, and make it less painful.

You should know that among tourists who are physically unprepared for high-mountain travel, the vital capacity of the lungs at the beginning of the hike even decreases somewhat, the maximum performance of the heart (compared to trained participants) also becomes less by 8-10%, and the reaction of increasing hemoglobin and red blood cells with oxygen deficiency is delayed.

Directly during the hike, the following activities are carried out: active acclimatization, psychotherapy and psychoprophylaxis, organization of appropriate nutrition, use of vitamins and adaptogens (medicines that increase the body’s performance), complete cessation of smoking and alcohol, systematic monitoring of health, and the use of certain medications.

Active acclimatization for mountaineering and for high-mountain hiking trips has differences in the methods of its implementation. This difference is explained primarily by the significant difference in the heights of the climbing objects. So, if for climbers this height can be 8842 m, then for the most prepared tourist groups it will not exceed 6000-6500 m (several passes in the area of ​​the High Wall, Zaalaisky and some others ridges in the Pamirs). The difference is that climbing to the peaks along technically difficult routes takes several days, and along complex traverses even weeks (without a significant loss of altitude at individual intermediate stages), while in high-mountain hiking trips, which are usually longer, less time is spent on overcoming passes.

Lower altitudes, a shorter period of stay at these altitudes and a faster descent with a significant loss of altitude greatly facilitate the acclimatization process for tourists, and a sufficiently repeated alternation of ascents and descents softens, or even stops, the development of altitude sickness.

Therefore, climbers during high-altitude ascents are forced to allocate up to two weeks at the beginning of the expedition for training (acclimatization) ascents to lower peaks, which differ from the main object of ascent to an altitude of about 1000 meters. For tourist groups whose routes pass through passes with a height of 3000-5000 m, special acclimatization exits are not required. For this purpose, as a rule, it is enough to choose a route such that during the first week - 10 days the height of the passes traversed by the group would gradually increase.

Since the greatest discomfort caused by the general fatigue of a tourist who has not yet become involved in the hiking life is usually felt in the first days of the hike, even when organizing a day trip at this time, it is recommended to conduct classes on movement techniques, on the construction of snow huts or caves, as well as reconnaissance or training trips to heights. These practical exercises and activities should be carried out at a good pace, which forces the body to react more quickly to thin air and to more actively adapt to changes in climatic conditions. N. Tenzing’s recommendations are interesting in this regard: at altitude, even in a bivouac, you need to be physically active - heat snow water, monitor the condition of the tents, check your equipment, move more, for example, after setting up the tents, take part in the construction of a snow kitchen, help distribute ready-made food to the tents.

Proper nutrition is also essential in the prevention of mountain sickness. At an altitude of more than 5000 m, the daily diet should have at least 5000 large calories. The carbohydrate content in the diet should be increased by 5-10% compared to normal nutrition. In areas associated with intense muscle activity, you should first consume an easily digestible carbohydrate - glucose. Increased consumption of carbohydrates contributes to the formation of more carbon dioxide, which the body lacks. The amount of fluid consumed in high altitude conditions and especially when performing intensive work associated with movement along difficult sections of the route should be at least 4-5 liters per day. This is the most decisive measure to combat dehydration. In addition, an increase in the volume of fluid consumed promotes the removal of under-oxidized metabolic products from the body through the kidneys.

The human body performing long-term intensive work in high altitude conditions requires an increased (2-3 times) amount of vitamins, especially those that are part of enzymes involved in the regulation of redox processes and closely related to metabolism. These are B vitamins, where the most important are B₁₂ and B₁₅, as well as B₁, B₂ and B₆. Thus, vitamin B₁₅, in addition to the above, helps to increase the body’s performance at altitude, significantly facilitating the performance of large and intense loads, increases the efficiency of oxygen use, activates oxygen metabolism in tissue cells, and increases resistance to high altitudes. This vitamin enhances the mechanism of active adaptation to lack of oxygen, as well as the oxidation of fats at altitude.

In addition to them, vitamins C, PP and folic acid play an important role in combination with iron glycerophosphate and metacil. This complex has an effect on increasing the number of red blood cells and hemoglobin, that is, increasing the oxygen capacity of the blood.

The acceleration of adaptation processes is also influenced by the so-called adaptogens - ginseng, Eleutherococcus and acclimatizin (a mixture of Eleutherococcus, Schisandra and yellow sugar). E. Gippenreiter recommends the following complex of drugs that increase the body’s adaptability to hypoxia and alleviate the course of mountain sickness: eleutherococcus, diabazole, vitamins A, B₁, B₂, B₆, B₁₂, C, PP, calcium pantothenate, methionine, calcium gluconate, calcium glycerophosphate and potassium chloride. The mixture proposed by N. Sirotinin is also effective: 0.05 g of ascorbic acid, 0.5 g of citric acid and 50 g of glucose per dose. We can also recommend a dry blackcurrant drink (in briquettes of 20 g), containing citric and glutamic acids, glucose, sodium chloride and sodium phosphate.

How long after returning to the plain does the body retain the changes that occurred in it during the process of acclimatization?

At the end of a trip in the mountains, depending on the altitude of the route, changes in the respiratory system, blood circulation and the composition of the blood itself acquired during the process of acclimatization pass quite quickly. Thus, the increased hemoglobin content decreases to normal in 2-2.5 months. Over the same period, the increased ability of the blood to carry oxygen also decreases. That is, the body’s acclimatization to altitude lasts only up to three months.