As soon as a person ascends into the mountains and overcomes a certain altitude barrier (usually from 2500 m above sea level), they encounter reduced atmospheric pressure and lower oxygen content. Upon entering such a hostile environment, the body begins to adapt to the changes. This process is accompanied by a deterioration in well-being and painful conditions. This is referred to as altitude sickness, and the period during which the body adapts to high altitudes is called acclimatization.
Essentially, altitude sickness is altitude hypoxia, which is exacerbated by physical exertion and harsh environmental conditions in the mountains: physical strain, cold, limited nutrition, and high humidity.
As altitude increases, each breath contains less oxygen. With increasing physical exertion in the mountains, the body's demand for oxygen additionally rises. During the acclimatization process, the human body attempts to adapt, resulting in:
• rapid breathing, which increases gas exchange in the lungs;
• an increase in the number of red blood cells, allowing the blood to carry more oxygen;
• increased heart rate and elevated blood pressure, enhancing arterial blood flow to the brain and muscles.
Changes in metabolic processes and blood composition are the essence of acclimatization. The main acclimatization occurs in the first 2-3 days in the mountains. After this period, a person can manage with less oxygen in the air and use energy more efficiently.
The term "altitude sickness" encompasses three types of disorders related to hypoxia: acute mountain sickness, high altitude pulmonary edema, and high altitude cerebral edema. If acclimatization is incorrect or incomplete, these can manifest either separately or in various combinations.
Acute Mountain Sickness
This is the most common form of altitude sickness. It is characterized by headaches and at least one of the following symptoms: rapid fatigue, dizziness, nausea or vomiting, loss of appetite, poor sleep. Typically, these symptoms manifest in various combinations within 4-12 hours after ascending to an altitude of 2500 m or higher.
Acute mountain sickness is unpleasant but does not pose a direct threat to a person's life. If no further ascent occurs, symptoms generally resolve within 24-48 hours.
High Altitude Pulmonary Edema
The risk of developing pulmonary edema is possible on the second day of staying at an altitude of 3000 m or more. Initial symptoms are usually nonspecific and similar to those of AMS: rapid fatigue and shortness of breath. As the condition progresses, shortness of breath occurs even at rest, a non-productive cough develops, bubbling sounds are heard in the lungs, and frothy or bloody sputum may appear (in severe cases), along with cyanosis (bluish discoloration of the lips, tongue, and nails) and a rise in temperature.
If pulmonary edema is suspected, it is essential to begin descending as quickly as possible. HAPE develops rapidly and can lead to death within a few hours (mortality rate of 50 percent). With timely assistance and immediate descent, it can resolve without health consequences.
High Altitude Cerebral Edema
Cerebral edema is the least common but the most dangerous form of altitude sickness. It typically occurs starting at an altitude of 4000 m and manifests on the second day. Typical symptoms of HACE include loss of coordination, unusual behavior (aggression, apathy, nervousness, etc.), impaired vision, hallucinations, severe headache, dizziness, vomiting, and loss of consciousness.
If HACE is suspected, urgent descent and medical assistance are required. Delays are unacceptable, as the consequences are irreversible, and the condition progresses very quickly, potentially leading to death within a few hours (mortality rate of 80 percent).
The occurrence of altitude sickness is influenced not only by altitude but also by a number of other factors:
The following individual factors affect the development of altitude sickness:
· individual tolerance to oxygen deficiency (for example, among mountain dwellers);
· gender (women tolerate hypoxia better);
· age (young people tolerate hypoxia poorly);
· physical, mental, and moral state;
· level of fitness;
· speed of ascent;
· degree and duration of oxygen deprivation;
· intensity of muscular efforts;
· past "altitude" experience.
The following factors provoke the development of altitude sickness and reduce tolerance to high altitudes:
· presence of alcohol or caffeine in the blood;
· insomnia, overexertion;
· psycho-emotional stress;
· hypothermia;
· poor quality and irrational nutrition;
· disruption of water-salt balance, dehydration;
· excessive body weight;
· respiratory and other chronic diseases (e.g., angina, bronchitis, pneumonia, chronic purulent stomatitis);
· blood loss.
The following climatic factors contribute to the development and more rapid progression of altitude sickness:
· Low temperatures — as altitude increases, the average annual air temperature gradually decreases by 0.5 °C for every 100 m of altitude (0.4 °C in winter, 0.6 °C in summer). In winter, the incidence of illness is more frequent at the same altitudes than in summer (see pathogenesis for reasons).
Sudden temperature changes also have an adverse effect.
· Humidity — at high altitudes, due to low temperatures, the partial pressure of water vapor is low. At an altitude of 2000 m and above, humidity is half that at sea level in the same area. At greater mountain heights, the air becomes almost dry (the partial pressure of saturated water vapor is negligible). This leads to increased fluid loss from the body through the skin and lungs, and consequently to dehydration.
· Wind — high in the mountains, winds can reach hurricane force (over 200 km/h), which cools the body, physically and mentally exhausts it, and makes breathing difficult.
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