Atmospheric pressure in the mountains. The higher the mountains, the higher the pressure.

The higher a person climbs into the mountains, or the higher his plane takes him, the thinner the air becomes. At an altitude of 5.5 km above sea level, atmospheric pressure is almost halved; the oxygen content also decreases to the same extent. Already at an altitude of 4 km, an untrained person can get the so-called mountain sickness. However, through training, you can accustom the body to stay at higher altitudes. Even when conquering Everest, the climbing heroes did not use oxygen devices. How does the body adapt to oxygen-poor air?

The main role here is played by an increase in the number, and hence an increase in the amount of hemoglobin in the blood. Residents mountainous areas the number of red blood cells reaches 6 or more million in 1 mm 3 (instead of 4 million under normal conditions). It is clear that in this case, the blood gets the opportunity to capture more oxygen from the air.

By the way, sometimes people who have been in Kislovodsk attribute the increase in the amount of hemoglobin in their blood to the fact that they had a good rest and recovered. The point, of course, is not only in this, but simply in the influence of the highlands.

Divers and those who work in caissons - special chambers used in the construction of bridges and other hydraulic structures, are forced, on the contrary, to work at high blood pressure air. At a depth of 50 m under water, a diver experiences pressure almost 5 times higher than atmospheric pressure, and in fact he sometimes has to go down 100 m or more under water.

Air pressure has a very peculiar effect. A person works in these conditions for hours without experiencing any trouble from increased pressure. However, with a quick rise up, sharp pains in the joints, itching appear,; in severe cases noted deaths. Why is this happening?

In everyday life, we do not always think about the force with which pressure on us atmospheric air. Meanwhile, its pressure is very high and amounts to about 1 kg per square centimeter of the body surface. The latter in a person of average height and weight is 1.7 m 2. As a result, the atmosphere presses on us with a force of 17 tons! We do not feel this huge squeezing effect because it is balanced by the pressure of body fluids and gases dissolved in them. fluctuations atmospheric pressure cause a number of shifts in the body, which is especially felt by patients with hypertension and diseases of the joints. After all, when the atmospheric pressure changes by 25 mm Hg. Art. the pressure of the atmosphere on the body changes by more than half a ton! The body must balance this pressure shift.

However, as already mentioned, being under pressure even at 10 atmospheres is relatively well tolerated by a diver. Why can a quick rise be fatal? The fact is that in the blood, as in any other liquid, with an increased pressure of the gases (air) in contact with it, these gases dissolve more significantly. Nitrogen, which makes up 4/5 of the air, is completely indifferent to the body (when it is in the form of a free gas), dissolves in large quantities in the diver's blood. If the air pressure decreases rapidly, the gas begins to come out of solution, the blood "boils", releasing nitrogen bubbles. These bubbles are formed in the vessels and can clog the vital important artery- in, the brain, etc. Therefore, divers and working caissons are very slowly raised to the surface so that the gas is released only from the pulmonary capillaries.

As different as the effects of being high above sea level and deep underwater, there is one link that connects them. If a person very quickly rises by plane into the rarefied layers of the atmosphere, then above 19 km above sea level, complete sealing is needed. At this altitude, the pressure decreases so much that water (and therefore blood) boils no longer at 100 ° C, but at . There may be phenomena of decompression sickness, similar in origin to decompression sickness.

First, let's remember the physics course high school, which explains why and how atmospheric pressure changes with altitude. The higher the area above sea level, the lower the pressure there. The explanation is very simple: atmospheric pressure indicates the force with which a column of air presses on everything that is on the surface of the Earth. Naturally, the higher you rise, the lower will be the height of the air column, its mass and the pressure exerted.

In addition, at a height the air is rarefied, it contains a much smaller number of gas molecules, which also instantly affects the mass. And we must not forget that with increasing altitude, the air is cleared of toxic impurities, exhaust gases and other "charms", as a result of which its density decreases, and atmospheric pressure indicators fall.

Studies have shown that the dependence of atmospheric pressure on altitude differs as follows: an increase of ten meters causes a decrease in the parameter by one unit. As long as the height of the terrain does not exceed five hundred meters above sea level, changes in the pressure of the air column are practically not felt, but if you rise five kilometers, the values ​​\u200b\u200bare half the optimal ones. The strength of the pressure exerted by the air also depends on the temperature, which decreases very much when ascending to a great height.

For blood pressure level and general condition human body the value of not only atmospheric, but also partial pressure, which depends on the concentration of oxygen in the air, is very important. In proportion to the decrease in air pressure values, the partial pressure of oxygen also decreases, which leads to an insufficient supply of this necessary element to the cells and tissues of the body and the development of hypoxia. This is explained by the fact that the diffusion of oxygen into the blood and its subsequent transportation to the internal organs occurs due to the difference in the values ​​of the partial pressure of the blood and the pulmonary alveoli, and when ascending to a great height, the difference in these readings becomes significantly smaller.

How does altitude affect a person's well-being?

The main negative factor affecting the human body at altitude is the lack of oxygen. It is as a result of hypoxia that acute disorders of the heart and blood vessels, increased blood pressure, digestive disorders and a number of other pathologies develop.

Hypertensive patients and people prone to pressure surges should not climb high into the mountains and it is advisable not to make many hours of flights. They will also have to forget about professional mountaineering and mountain tourism.

The severity of the changes occurring in the body made it possible to identify several height zones:

• Up to one and a half - two kilometers above sea level is a relatively safe zone in which there are no special changes in the functioning of the body and the state of vital systems. Deterioration of well-being, a decrease in activity and endurance is observed very rarely.
• From two to four kilometers - the body tries to cope with oxygen deficiency on its own, thanks to increased breathing and deep breaths. Heavy physical work, which requires a large amount of oxygen consumption, is difficult to perform, but the light load is well tolerated for several hours.
• From four to five and a half kilometers - the state of health noticeably worsens, the performance of physical work is difficult. Psycho-emotional disorders appear in the form of elation, euphoria, inappropriate actions. With a long stay at such a height, headaches, a feeling of heaviness in the head, problems with concentration, and lethargy occur.
• From five and a half to eight kilometers - it is impossible to engage in physical work, the condition deteriorates sharply, the percentage of loss of consciousness is high.
• Above eight kilometers - at such a height a person is able to maintain consciousness for a maximum of several minutes, followed by a deep fainting and death.

For the flow of metabolic processes in the body, oxygen is needed, the deficiency of which at altitude leads to the development of mountain sickness. The main symptoms of the disorder are:

• Headache.
• Shortness of breath, shortness of breath, shortness of breath.
• Nose bleed.
• Nausea, bouts of vomiting.
• Joint and muscle pain.
• Sleep disorders.
• Psycho-emotional disorders.

At high altitude, the body begins to experience a lack of oxygen, as a result of which the work of the heart and blood vessels is disturbed, arterial and intracranial pressure rises, and vital internal organs fail. To successfully overcome hypoxia, you need to include nuts, bananas, chocolate, cereals, fruit juices in your diet.

Influence of height on the level of blood pressure

When climbing to a great height and rarefied air cause an increase in heart rate, an increase in blood pressure. However, with a further increase in altitude, the level of blood pressure begins to decrease. A decrease in the oxygen content in the air to critical values ​​\u200b\u200bcauses depression of cardiac activity, a noticeable decrease in pressure in the arteries, while in the venous vessels the indicators increase. As a result, a person develops arrhythmia, cyanosis.

Not so long ago, a group of Italian researchers decided for the first time to study in detail how altitude affects blood pressure levels. To conduct research, an expedition to Everest was organized, during which the pressure indicators of the participants were determined every twenty minutes. During the trip, an increase in blood pressure during ascent was confirmed: the results showed that the systolic value increased by fifteen, and the diastolic value by ten units. It was noted that the maximum values ​​of blood pressure were determined at night. The effect of antihypertensive drugs at different heights was also studied. It turned out that the studied drug effectively helped at a height of up to three and a half kilometers, and when climbing above five and a half it became absolutely useless.

Atmospheric pressure - the pressure of the atmosphere on all objects in it and the Earth's surface. Atmospheric pressure is created by the gravitational attraction of air to the Earth. Atmospheric pressure is measured with a barometer. Normal atmospheric pressure is the pressure at sea level at 15°C. It is equal to 760 mm Hg. Art. (International standard atmosphere - ISA, 101 325 Pa).

Even in ancient times, people noticed that air exerts pressure on ground objects, especially during storms and hurricanes. He used this pressure, forcing the wind to move sailing ships, to rotate the wings of windmills. However, for a long time it was not possible to prove that air has weight. Only in the 17th century was an experiment that proved the weight of air. The reason for this was a random circumstance.

In Italy, in 1640, the Duke of Tuscany decided to arrange a fountain on the terrace of his palace. The water for this fountain had to be pumped from a nearby lake, but the water did not rise above 32 feet (10.3m). The duke turned to Galileo, then already a very old man, for clarification. The great scientist was confused and did not immediately find how to explain this phenomenon. And only a student of Galileo, Torricelli, after long experiments, proved that air has weight, and the pressure of the atmosphere is balanced by a column of water of 32 feet, or 10.3 m.

The search for the reasons for this and experiments with a heavier substance - mercury, undertaken by Evangelista Torricelli led to the fact that in 1643 he proved that air has weight. Together with V. Viviani, Torricelli conducted the first experiment on measuring atmospheric pressure, inventing the Torricelli tube (the first mercury barometer), a glass tube in which there is no air. In such a tube, mercury rises to a height of about 760 mm.

Thus, since air has mass and weight, it exerts pressure on the surface in contact with it. It is calculated that a column of air from sea level to the upper limit of the atmosphere presses on an area of ​​1 cm with the same force as a weight of 1 kg 33 g. Man and all other living organisms do not feel this pressure, since it is balanced by their internal air pressure. When climbing in the mountains, already at an altitude of 3000 m, a person begins to feel bad: shortness of breath and dizziness appear. At an altitude of more than 4000 m, nosebleeds can bleed, as blood vessels burst, sometimes a person even loses consciousness. All this happens because atmospheric pressure decreases with height, the air becomes rarefied, the amount of oxygen in it decreases, and the internal pressure of a person does not change. Therefore, in aircraft flying at high altitude, the cabins are hermetically sealed, and the same air pressure is artificially maintained in them as at the surface of the Earth.

It has been established that at sea level at the 45° parallel at an air temperature of 0°C, atmospheric pressure is close to the pressure produced by a mercury column 760 mm high. The air pressure under such conditions is called normal atmospheric pressure. If the pressure indicator is greater, then it is considered increased, if it is less, it is considered reduced. When climbing mountains, for every 10.5 m, the pressure decreases by about 1 mmHg. Knowing how pressure changes, using a barometer, you can calculate the height of a place.

When a head starts to hurt before a thunderstorm, and every cell of the body feels the approach of rain, you begin to think that this is old age. In fact, this is how millions of people react to changeable weather on the globe.

This process is called meteorological dependence. The first factor that directly affects well-being is the close relationship between atmospheric and blood pressure.

What is atmospheric pressure

Atmospheric pressure is a physical quantity. It is characterized by the action of force air masses per unit area. Its value is changeable, depends on the height of the area above sea level, geographical latitude and is associated with the weather. Normal atmospheric pressure is 760 mm Hg. It is at this value that a person experiences the most comfortable state of health.

What determines the change in atmospheric pressure

The deviation of the barometer needle by 10 mm in one direction or another is sensitive to humans. And pressure drops occur for several reasons.

seasonality

In summer, when the air warms up, the pressure on the mainland drops to a minimum. AT winter period, due to the heavy and cold air, the values ​​of the barometer needle reach a maximum.

Times of Day

In the morning and in the evening, the pressure usually rises slightly, after noon and midnight it becomes lower.

Zoning

Atmospheric pressure also has a pronounced zonal character. On the globe, areas with a predominance of high and low pressure are distinguished. This happens because the surface of the Earth warms up unevenly.

At the equator, where the land is very hot, warm air rises and areas are formed where the pressure is low. Closer to the poles cold heavy air descends to the ground, presses on the surface. Accordingly, a high pressure zone is formed here.

Does the pressure rise or fall in the mountains?

Recall the geography course for high school. As the altitude increases, the air becomes thinner and the pressure decreases. Every twelve meters of ascent reduce the barometer reading by 1 mm Hg. But at high altitudes, the patterns are different.

See the table for how air temperature and pressure change with climb.

How are atmospheric pressure and blood pressure related?

So, if you climb Mount Belukha (4,506 m), from the foot to the top, the temperature will drop by 30 ° C, and the pressure will drop by 330 mm Hg. That's why high-altitude hypoxia, oxygen starvation, or a miner occurs in the mountains!

Man is so arranged that over time he gets used to new conditions. Stable weather has set in - all body systems work without failures, the dependence of arterial pressure on atmospheric pressure is minimal, the condition is normalizing. And during periods of change of cyclones and anticyclones, go to new mode the body fails to work quickly, the state of health worsens, it can change, jump blood pressure.

Arterial, or blood, is the pressure of blood on the walls of blood vessels - veins, arteries, capillaries. It is responsible for the uninterrupted movement of blood through all the vessels of the body, and directly depends on the atmospheric pressure.

First of all, people with chronic heart diseases and of cardio-vascular system(perhaps the most common disease is hypertension).

Also at risk are:

• Patients with neurological disorders and nervous exhaustion;
• Allergy sufferers and people with autoimmune diseases;
• Patients with mental disorders, obsessive fears and anxiety;
• People suffering from lesions of the articular apparatus.

How does a cyclone affect the human body?

A cyclone is an area with low atmospheric pressure. The thermometer falls to the level of 738-742 mm. rt. Art. The amount of oxygen in the air decreases.

In addition, the following signs distinguish low atmospheric pressure:

• High humidity and air temperature,
• cloudy,
• Precipitation in the form of rain or snow.

People with diseases of the respiratory system, cardiovascular system and hypotension suffer from such a change in the weather. Under the influence of the cyclone, they experience weakness, lack of oxygen, shortness of breath, shortness of breath.

In some weather-sensitive people, intracranial pressure rises, a headache occurs, and disorders of the gastrointestinal tract occur.

What features need to be considered hypotension

How does a cyclone affect people with low blood pressure? With a decrease in atmospheric pressure, arterial pressure also becomes lower, the blood is saturated with oxygen worse, the result is headaches, weakness, a feeling of lack of air, and a desire to sleep. Oxygen starvation can lead to a hypotensive crisis and coma.

Video: Atmospheric pressure and human well-being

We will tell you what to do at low atmospheric pressure. Hypotension patients with the onset of a cyclone need to control blood pressure. It is believed that pressure from 130/90 mm Hg, increased for hypotension, may be accompanied by symptoms of a hypertensive crisis.

Therefore, you need to drink more fluids, get enough sleep. In the morning you can drink a cup of strong coffee or 50 g of cognac. To prevent meteorological dependence, you need to harden the body, take strengthening nervous system vitamin complexes, tincture of ginseng or eleutherococcus.

How does an anticyclone affect the body?

With the onset of an anticyclone, the barometer needles crawl up to the level of 770-780 mm Hg. The weather changes: it becomes clear, sunny, a light breeze blows. The amount of industrial impurities harmful to health is increasing in the air.

High blood pressure is not dangerous for hypotensive patients.

But, if it rises, then allergy sufferers, asthmatics, hypertensive patients experience negative manifestations:

• Headaches and heartaches
• Decreased performance,
• increased heart rate,
• Redness of the face and skin,
• flies flickering before my eyes,
• An increase in blood pressure.

Also, the number of leukocytes in the blood decreases, which means that a person becomes vulnerable to diseases. With blood pressure of 220/120 mm Hg. high risk of developing a hypertensive crisis, thrombosis, embolism, coma .

Doctors advise patients with blood pressure above normal to alleviate the condition to carry out gymnastics complexes, arrange contrasting water procedures, eat vegetables and fruits containing potassium. These are: peaches, apricots, apples, Brussels sprouts and cauliflower, spinach.

Also avoid serious physical activity try to get more rest. When the air temperature rises, drink more liquid: clean drinking water, tea, juices, fruit drinks.

Video: How high and low atmospheric pressure affects hypertensive patients

Can weather sensitivity be reduced?

It is possible to reduce weather dependence if you follow the simple but effective recommendations of doctors.

1. banal advice, follow the daily routine. Go to bed early, sleep at least 9 hours. This is especially true for days when the weather changes.
2. Before bedtime drink a glass of mint or chamomile tea . It's calming.
3. Do a light workout in the morning, stretch, massage your feet.
4. After gymnastics take a contrast shower.
5. Get in a positive mood. Remember that a person cannot influence the increase or decrease in atmospheric pressure, but help the body cope with its fluctuations in our strength.

Summary: meteorological dependence is typical for patients with pathologies of the heart and blood vessels, as well as for elderly people suffering from a bunch of diseases. At risk for allergies, asthma, hypertension. The most dangerous for weather-sensitive people are sharp jumps in atmospheric pressure. Saves from unpleasant sensations hardening of the body and healthy lifestyle life.

When climbing mountains, atmospheric pressure

In the Homework section, to the question of what happens to pressure and air when climbing mountains, the best answer given by the author Liza Zakharova is Since air has mass and weight, it exerts pressure on the surface in contact with it.

It is calculated that a column of air from sea level to the upper limit of the atmosphere presses on an area of ​​1 cm with the same force as a weight of 1 kg 33 g. Man and all other living organisms do not feel this pressure, since it is balanced by their internal air pressure. When climbing in the mountains, already at an altitude of 3000 m, a person begins to feel bad: shortness of breath and dizziness appear. At an altitude of more than 4000 m, nosebleeds can bleed, as blood vessels burst, sometimes a person even loses consciousness. All this happens because atmospheric pressure decreases with height, the air becomes rarefied, the amount of oxygen in it decreases, and the internal pressure of a person does not change. Therefore, in aircraft flying at high altitude, the cabins are hermetically sealed, and the same air pressure is artificially maintained in them as at the surface of the Earth. Pressure is measured using a special device - a barometer - in mmHg.

Atmosphere pressure

Atmospheric pressure - the pressure of the atmosphere on all objects in it and the Earth's surface. Atmospheric pressure is created by the gravitational attraction of air to the Earth. Atmospheric pressure is measured with a barometer. Normal atmospheric pressure is the pressure at sea level at 15°C. It is equal to 760 mm Hg. Art. (International Standard Atmosphere - ISA, Pa).

Even in ancient times, people noticed that air exerts pressure on ground objects, especially during storms and hurricanes. He used this pressure, forcing the wind to move sailing ships, to rotate the wings of windmills. However, for a long time it was not possible to prove that air has weight. Only in the 17th century was an experiment that proved the weight of air. The reason for this was a random circumstance.

In Italy, in 1640, the Duke of Tuscany decided to arrange a fountain on the terrace of his palace. The water for this fountain had to be pumped from a nearby lake, but the water did not rise above 32 feet (10.3m). The duke turned to Galileo, then already a very old man, for clarification. The great scientist was confused and did not immediately find how to explain this phenomenon. And only a student of Galileo, Torricelli, after long experiments, proved that air has weight, and the pressure of the atmosphere is balanced by a column of water of 32 feet, or 10.3 m.

The search for the reasons for this and experiments with a heavier substance - mercury, undertaken by Evangelista Torricelli led to the fact that in 1643 he proved that air has weight. Together with V. Viviani, Torricelli conducted the first experiment on measuring atmospheric pressure, inventing the Torricelli tube (the first mercury barometer), a glass tube in which there is no air. In such a tube, mercury rises to a height of about 760 mm.

Thus, since air has mass and weight, it exerts pressure on the surface in contact with it. It is calculated that a column of air from sea level to the upper limit of the atmosphere presses on an area of ​​1 cm with the same force as a weight of 1 kg 33 g. Man and all other living organisms do not feel this pressure, since it is balanced by their internal air pressure. When climbing in the mountains, already at an altitude of 3000 m, a person begins to feel bad: shortness of breath and dizziness appear. At an altitude of more than 4000 m, nosebleeds can bleed, as blood vessels burst, sometimes a person even loses consciousness. All this happens because atmospheric pressure decreases with height, the air becomes rarefied, the amount of oxygen in it decreases, and the internal pressure of a person does not change. Therefore, in aircraft flying at high altitude, the cabins are hermetically sealed, and the same air pressure is artificially maintained in them as at the surface of the Earth.

It has been established that at sea level at the 45° parallel at an air temperature of 0°C, atmospheric pressure is close to the pressure produced by a mercury column 760 mm high. The air pressure under such conditions is called normal atmospheric pressure. If the pressure indicator is greater, then it is considered increased, if it is less, it is considered reduced. When climbing mountains, for every 10.5 m, the pressure decreases by about 1 mmHg. Knowing how pressure changes, using a barometer, you can calculate the height of a place.

Atmosphere pressure

Since air has mass and weight, it exerts pressure on the surface in contact with it. It is calculated that a column of air from sea level to the upper limit of the atmosphere presses on an area of ​​1 cm with the same force as a weight of 1 kg 33 g. Man and all other living organisms do not feel this pressure, since it is balanced by their internal air pressure. When climbing in the mountains, already at an altitude of 3000 m, a person begins to feel bad: shortness of breath and dizziness appear. At an altitude of more than 4000 m, nosebleeds can bleed, as blood vessels burst, sometimes a person even loses consciousness. All this happens because atmospheric pressure decreases with height, the air becomes rarefied, the amount of oxygen in it decreases, and the internal pressure of a person does not change. Therefore, in aircraft flying at high altitude, the cabins are hermetically sealed, and the same air pressure is artificially maintained in them as at the surface of the Earth. Pressure is measured using a special device - a barometer - in mmHg.

It has been established that at sea level at the 45° parallel at an air temperature of 0°C, atmospheric pressure is close to the pressure produced by a mercury column 760 mm high. The air pressure under such conditions is called normal atmospheric pressure. If the pressure indicator is greater, then it is considered increased, if it is less, it is considered reduced. When climbing mountains, for every 10.5 m, the pressure decreases by about 1 mmHg. Knowing how pressure changes, using a barometer, you can calculate the height of a place.

Pressure doesn't just change with height. It depends on the air temperature and on the influence of air masses. Cyclones lower atmospheric pressure, while anticyclones increase it.

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How does atmospheric pressure change with height?

Atmospheric pressure decreases with altitude. This is due to two reasons. Firstly, the higher we are, the lower the height of the air column above us, and, therefore, less weight presses on us. Secondly, with height, the density of air decreases, it becomes more rarefied, that is, it has fewer gas molecules, and therefore it has less mass and weight.

Why does air density decrease with height? The earth attracts bodies that are in its gravitational field. The same applies to air molecules. They would all fall to the surface of the Earth, but their chaotic rapid movement, lack of interaction with each other, remoteness from each other make them scatter and occupy all possible space. However, the phenomenon of attraction to the Earth still causes more air molecules to be in the lower atmosphere.

However, the decrease in air density with height is significant if we consider the entire atmosphere, which is about a kilometer high. In fact, the lower layer of the atmosphere - the troposphere - contains 80% of the air mass and is only 8-18 km in height (the height varies depending on the geographical latitude and the season of the year). Here we can neglect the change in air density with height, assuming it to be constant.

In this case, only the change in altitude above sea level affects the change in atmospheric pressure. Then you can easily calculate exactly how atmospheric pressure changes with height.

The air density at sea level is 1.29 kg/m 3 . We will assume that it remains almost unchanged for several kilometers up. The pressure can be calculated using the formula p = ρgh. Here it should be understood that h is the height of the air column above the place where the pressure is measured. Most great importance h will be at the surface of the Earth. It will decrease with height.

Experiments show that normal atmospheric pressure at sea level is approximately 101.3 kPa or Pa. Find the approximate height of the air column above sea level. It is clear that this will not be a real height, since the air above is rarefied, but, as it were, the height of air “compressed” to the same density as at the Earth’s surface. But near the Earth's surface, we don't care.

h \u003d p / (ρg) \u003d Pa / (1.29 kg / m3 * 9.8 N / kg) ≈ 8013 m

And now we calculate the atmospheric pressure when lifting 1 km up (1000 m). Here the height of the air column will be 7013 m, then

p = (1.29 * 9.8 * 7013) Pa ≈Pa ≈ 89 kPa

That is, near the surface of the Earth, for every kilometer upward, the pressure decreases by approximately 12 kPa (101 kPa - 89 kPa).

2 Comments

Atmospheric pressure.

Posted by Yuriy Wed, 05/04/:24

They would all fall to the surface of the Earth, but their chaotic rapid movement, lack of interaction with each other, remoteness from each other make them scatter and occupy all possible space.

Hello. It should be added to your presentation - But they do not hesitate to peck a person by creating pressure.

Atmosphere

Posted by Aaeksander Thu 04/27/:04

It is necessary to clarify the accepted height of the atmosphere 100km -110km or 0000 meters. Sincerely!

Atmosphere pressure

The air surrounding our Earth has a significant mass and therefore exerts pressure on the earth's surface. Normal atmospheric pressure is the pressure of a mercury column 760 mm high with a cross section of 1 cm2 at a temperature of 0 ° C at sea level at a latitude of 45 °. Atmospheric pressure used to be measured in millimeters of mercury (mm Hg) in accordance with the scale of the first mercury barometer, invented at the dawn of the history of meteorology in the 17th century. Then atmospheric pressure began to be measured in millibars (mb), 760 mm Hg. Art. = 1013.25 mb.

Atmospheric pressure changes continuously both vertically and horizontally. As the height of the place increases, the pressure decreases, as the air column and its density decrease.

The main instrument for measuring atmospheric pressure is a mercury barometer. In it, atmospheric pressure is balanced by the pressure of a column of mercury. By changes in the height of the mercury column, one can judge changes in atmospheric pressure (Toricelli's experiment). Other devices (aneroid barograph) are based on determining the deformation of an elastic metal box from which air is pumped out; when the pressure increases, the bottom of the box is compressed, and when it decreases, it bends. These changes are transmitted to the hand, which moves on a dial divided into millimeters or millibars. Self-recording barometers-barographs are used to record changes in pressure over a certain period of time. Since the air in a closed (unpressurized) room equalizes its pressure with the outside air through pores and cracks, the difference between the atmospheric pressure in the room and outside is negligible, barometers at weather stations are placed indoors.

Atmospheric pressure is constantly changing. At a constant altitude, as the temperature rises, the pressure drops, and as the temperature rises, it rises. However, when climbing into the mountains, the pressure decreases, because. the mass of air exerting pressure on the surface is significantly reduced.

Changes in sea level pressure are shown on maps using isobars, lines on a map that connect points of equal atmospheric pressure.

Tip 1: How temperature and atmospheric pressure change in the mountains

• Grade 7 physics textbook, molecular physics textbook, barometer.

Atmospheric pressure can change during the day. Its performance also depends on the season. But, as a rule, such pressure surges occur within no more than twenty to thirty millimeters of mercury.

Such fluctuations are not noticeable to the body. healthy person. But for those suffering hypertension, rheumatism and other diseases, these changes can cause disturbances in the functioning of the body and deterioration in general well-being.

A person can feel a lower atmospheric pressure when he is on a mountain and takes off on an airplane. The main physiological factor in altitude is reduced atmospheric pressure and, consequently, reduced partial pressure of oxygen.

The body reacts to low atmospheric pressure, first of all, by increasing breathing. Oxygen at altitude is discharged. This causes excitation of the chemoreceptors of the carotid arteries, and it is transmitted to the medulla oblongata to the center, which is responsible for increased breathing. Through this process, the pulmonary ventilation of a person who experiences low atmospheric pressure increases in necessary limits and the body gets enough oxygen.

An important physiological mechanism that starts at low atmospheric pressure is the increased activity of the organs responsible for hematopoiesis. This mechanism manifests itself in an increase in the amount of hemoglobin and red blood cells in the blood. In this mode, the body is able to transport more oxygen.

How does altitude affect pressure levels?

First, let's take a high school physics course that explains why and how atmospheric pressure changes with altitude. The higher the area above sea level, the lower the pressure there. The explanation is very simple: atmospheric pressure indicates the force with which a column of air presses on everything that is on the surface of the Earth. Naturally, the higher you rise, the lower will be the height of the air column, its mass and the pressure exerted.

In addition, at a height the air is rarefied, it contains a much smaller number of gas molecules, which also instantly affects the mass. And we must not forget that with increasing altitude, the air is cleared of toxic impurities, exhaust gases and other "charms", as a result of which its density decreases, and atmospheric pressure indicators fall.

Studies have shown that the dependence of atmospheric pressure on altitude differs as follows: an increase of ten meters causes a decrease in the parameter by one unit. As long as the height of the terrain does not exceed five hundred meters above sea level, changes in the pressure of the air column are practically not felt, but if you rise five kilometers, the values ​​\u200b\u200bare half the optimal ones. The strength of the pressure exerted by the air also depends on the temperature, which decreases very much when ascending to a great height.

For the level of blood pressure and the general condition of the human body, the value of not only atmospheric, but also partial pressure, which depends on the concentration of oxygen in the air, is very important. In proportion to the decrease in air pressure values, the partial pressure of oxygen also decreases, which leads to an insufficient supply of this necessary element to the cells and tissues of the body and the development of hypoxia. This is explained by the fact that the diffusion of oxygen into the blood and its subsequent transportation to the internal organs occurs due to the difference in the values ​​of the partial pressure of the blood and the pulmonary alveoli, and when ascending to a great height, the difference in these readings becomes significantly smaller.

How does altitude affect a person's well-being?

The main negative factor affecting the human body at altitude is the lack of oxygen. It is as a result of hypoxia that acute disorders of the heart and blood vessels, increased blood pressure, digestive disorders and a number of other pathologies develop.

Hypertensive patients and people prone to pressure surges should not climb high into the mountains and it is advisable not to make many hours of flights. They will also have to forget about professional mountaineering and mountain tourism.

The severity of the changes occurring in the body made it possible to identify several height zones:

• Up to one and a half - two kilometers above sea level is a relatively safe zone in which there are no special changes in the functioning of the body and the state of vital systems. Deterioration of well-being, a decrease in activity and endurance is observed very rarely.
• From two to four kilometers - the body tries to cope with oxygen deficiency on its own, thanks to increased breathing and deep breaths. Heavy physical work, which requires a large amount of oxygen consumption, is difficult to perform, but the light load is well tolerated for several hours.
• From four to five and a half kilometers - the state of health noticeably worsens, the performance of physical work is difficult. Psycho-emotional disorders appear in the form of elation, euphoria, inappropriate actions. With a long stay at such a height, headaches, a feeling of heaviness in the head, problems with concentration, and lethargy occur.
• From five and a half to eight kilometers - it is impossible to engage in physical work, the condition deteriorates sharply, the percentage of loss of consciousness is high.
• Above eight kilometers - at such a height a person is able to maintain consciousness for a maximum of several minutes, followed by a deep fainting and death.

For the flow of metabolic processes in the body, oxygen is needed, the deficiency of which at altitude leads to the development of mountain sickness. The main symptoms of the disorder are:

• Headache.
• Shortness of breath, shortness of breath, shortness of breath.
• Nose bleed.
• Nausea, bouts of vomiting.
• Joint and muscle pain.
• Sleep disorders.
• Psycho-emotional disorders.

At high altitude, the body begins to experience a lack of oxygen, as a result of which the work of the heart and blood vessels is disturbed, arterial and intracranial pressure rises, and vital internal organs fail. To successfully overcome hypoxia, you need to include nuts, bananas, chocolate, cereals, fruit juices in your diet.

Influence of height on the level of blood pressure

When climbing to a great height, a decrease in atmospheric pressure and rarefied air cause an increase in heart rate, an increase in blood pressure. However, with a further increase in altitude, the level of blood pressure begins to decrease. A decrease in the oxygen content in the air to critical values ​​\u200b\u200bcauses depression of cardiac activity, a noticeable decrease in pressure in the arteries, while in the venous vessels the indicators increase. As a result, a person develops arrhythmia, cyanosis.

Not so long ago, a group of Italian researchers decided for the first time to study in detail how altitude affects blood pressure levels. To conduct research, an expedition to Everest was organized, during which the pressure indicators of the participants were determined every twenty minutes. During the trip, an increase in blood pressure during ascent was confirmed: the results showed that the systolic value increased by fifteen, and the diastolic value by ten units. It was noted that the maximum values ​​of blood pressure were determined at night. The effect of antihypertensive drugs at different heights was also studied. It turned out that the studied drug effectively helped at a height of up to three and a half kilometers, and when climbing above five and a half it became absolutely useless.

Breathing in the mountains and underwater

The higher a person climbs into the mountains, or the higher his plane takes him, the thinner the air becomes. At an altitude of 5.5 km above sea level, atmospheric pressure is almost halved; the oxygen content also decreases to the same extent. Already at an altitude of 4 km, an untrained person can get the so-called mountain sickness. However, through training, you can accustom the body to stay at higher altitudes. Even when conquering Everest, the climbing heroes did not use oxygen devices. How does the body adapt to oxygen-poor air?

The main role here is played by an increase in the number of red blood cells, and hence an increase in the amount of hemoglobin in the blood. In mountainous areas, the number of red blood cells reaches 6 or more million per 1 mm 3 (instead of 4 million under normal conditions). It is clear that in this case, the blood gets the opportunity to capture more oxygen from the air.

By the way, sometimes people who have been in Kislovodsk attribute the increase in the amount of hemoglobin in their blood to the fact that they had a good rest and recovered. The point, of course, is not only in this, but simply in the influence of the highlands.

Divers and those who work in caissons - special chambers used in the construction of bridges and other hydraulic structures, are forced, on the contrary, to work with increased air pressure. At a depth of 50 m under water, a diver experiences pressure almost 5 times higher than atmospheric pressure, and in fact he sometimes has to go down 100 m or more under water.

Air pressure has a very peculiar effect. A person works in these conditions for hours without experiencing any trouble from increased pressure. However, with a quick rise up, sharp pains in the joints, skin itching, and vomiting appear; in severe cases, deaths have been reported. Why is this happening?

In everyday life, we do not always think about the force with which atmospheric air presses on us. Meanwhile, its pressure is very high and amounts to about 1 kg per square centimeter of the body surface. The latter in a person of average height and weight is 1.7 m 2. As a result, the atmosphere presses on us with a force of 17 tons! We do not feel this huge squeezing effect because it is balanced by the pressure of body fluids and gases dissolved in them. Fluctuations in atmospheric pressure cause a number of shifts in the body, which is especially felt by patients with hypertension and joint diseases. After all, when the atmospheric pressure changes by 25 mm Hg. Art. the pressure of the atmosphere on the body changes by more than half a ton! The body must balance this pressure shift.

However, as already mentioned, being under pressure even at 10 atmospheres is relatively well tolerated by a diver. Why can a quick rise be fatal? The fact is that in the blood, as in any other liquid, with an increased pressure of the gases (air) in contact with it, these gases dissolve more significantly. Nitrogen, which makes up 4/5 of the air, is completely indifferent to the body (when it is in the form of a free gas), dissolves in large quantities in the diver's blood. If the air pressure decreases rapidly, the gas begins to come out of solution, the blood "boils", releasing nitrogen bubbles. These bubbles are formed in the vessels and can clog a vital artery - in the heart, brain, etc. Therefore, divers and working caissons are very slowly raised to the surface so that the gas is released only from the pulmonary capillaries.

As different as the effects of being high above sea level and deep underwater, there is one link that connects them. If a person very quickly rises by plane into the rarefied layers of the atmosphere, then above 19 km above sea level, complete sealing is needed. At this altitude, the pressure decreases so much that water (and therefore blood) boils no longer at 100 ° C, but at body temperature. There may be phenomena of decompression sickness, similar in origin to decompression sickness.