Help on Tele2, tariffs, questions

To maintain life, it is necessary, on the one hand, to continuously absorb oxygen by the cells of a living organism and, on the other, to remove carbon dioxide formed as a result of oxidation processes. These two parallel processes constitute the essence of breathing.

In highly organized multicellular animals, respiration is provided by special organs - the lungs.

The human lungs consist of many individual small pulmonary vesicles of the alveoli with a diameter of 0.2 mm. But since their number is very large (about 700 million), the total surface is significant and amounts to 90 m 2.

The alveoli are densely intertwined with a network of the finest blood vessels - capillaries. The wall of the pulmonary vesicle and capillary together is only 0.004 mm thick.

Thus, the blood flowing through the capillaries of the lungs comes into extremely close contact with the air in the alveoli, where gas exchange occurs.

Atmospheric air enters the pulmonary vesicles, passing through the airways.

The respiratory tract itself begins with the so-called larynx at the place where the pharynx passes into the esophagus. The larynx is followed by the windpipe - the trachea with a diameter of about 20 mm, in the walls of which there are cartilaginous rings (Fig. 7).

Rice. 7. Upper breathing paths:
1 - nasal cavity: 2 - oral cavity; 3 - esophagus; 4 - larynx and windpipe (trachea); 5 - epiglottis

The trachea passes into the chest cavity, where it divides into two large bronchi - the right and left, on which the right and left lungs hang. Having entered the lung, the bronchus branches, its branches (medium and small bronchi) gradually become thinner and, finally, pass into the thinnest terminal branches - bronchioles, on which the alveoli sit.

The outside of the lungs is covered with a smooth, slightly moist membrane - the pleura. Exactly the same membrane covers the inside of the wall of the chest cavity, formed on the sides by the ribs and intercostal muscles, and below by the diaphragm or the pectoral muscle.

Normally, the lungs are not fused to the walls of the chest, they are only pressed tightly against them. This occurs because there is no air in the pleural cavities (between the pleural membranes of the lungs and chest walls), which are like narrow slits. Inside the lungs, in the alveoli, there is always air that communicates with the atmospheric air, so there is (on average) atmospheric pressure in the lungs. It presses the lungs against the walls of the chest with such force that the lungs cannot tear themselves away from them and passively follow them as the chest expands or contracts.

Blood, making a continuous circulation through the vessels of the alveoli, captures oxygen and releases carbon dioxide (CO 2). Therefore, for proper gas exchange it is necessary that the air in the lungs contains the required amount of oxygen and is not overfilled with CO 2 (carbon dioxide). This is ensured by constant partial renewal of air in the lungs. When you inhale, fresh atmospheric air enters the lungs, and when you exhale, the already used air is removed.

Breathing occurs as follows. During inhalation, the force of the respiratory muscles expands the chest. The lungs, passively following the chest, suck in air through the respiratory tract. Then the chest, due to its elasticity, decreases in volume, the lungs compress and push excess air into the atmosphere. Exhalation occurs. During quiet breathing, 500 ml of air enters the lungs of a person during each breath. He exhales the same amount. This air is called breathing air. But if, after a normal inhalation, you take a deep breath, then another 1500-3000 ml of air will enter the lungs. It is called additional. In addition, when exhaling deeply after normal exhalation, up to 1000-2500 ml of so-called reserve air can be removed from the lungs. However, even after this, about 1000-1200 ml of residual air remains in the lungs.

The sum of the volume of respiratory, additional and reserve air is called the vital capacity of the lungs. It is measured using a special device - a spirometer. In different people, the vital capacity of the lungs ranges from 3000 to 6000-7000 ml.

A high vital capacity is essential for divers. The larger the lung capacity, the further underwater a diver can stay.

Breathing is regulated by special nerve cells - the so-called respiratory center, which is located next to the vasomotor center in the medulla oblongata.

The respiratory center is very sensitive to excess carbon dioxide in the blood. An increase in carbon dioxide in the blood irritates the respiratory center and increases breathing speed. Conversely, a sharp decrease in the carbon dioxide content in the blood or alveolar air causes a short-term cessation of breathing (apnea) for 1-1.5 minutes.

Breathing is under some control of the will. A healthy person can voluntarily hold his breath for 45-60 seconds.

The concept of gas exchange in the body(external and internal breathing). External respiration ensures gas exchange between the outside air and human blood, saturates the blood with oxygen and removes carbon dioxide from it. Internal respiration ensures the exchange of gases between the blood and tissues of the body.

The exchange of gases in the lungs and tissues occurs as a result of the difference in partial pressures of gases in the alveolar air, blood and tissues. Venous blood flowing to the lungs is poor in oxygen and rich in carbon dioxide. The partial pressure of oxygen in it (60-76 mm Hg) is significantly less than in the alveolar air (100-110 mm Hg), and oxygen freely passes from the alveoli into the blood. But the partial pressure of carbon dioxide in the venous blood (48 mm Hg) is higher than in the alveolar air (41.8 mm Hg), which forces carbon dioxide to leave the blood and pass into the alveoli, from where it is removed during exhalation . In the tissues of the body, this process occurs differently: oxygen from the blood enters the cells, and the blood is saturated with carbon dioxide, which is found in abundance in the tissues.

The relationship between the partial pressures of oxygen and carbon dioxide in atmospheric air, blood and body tissues can be seen from the table (the partial pressure values ​​are expressed in mmHg).

It should be added that a high percentage of carbon dioxide in the blood or tissues promotes the decomposition of hemoglobin oxide into hemoglobin and pure oxygen, and a high oxygen content promotes the removal of carbon dioxide from the blood through the lungs.

Features of breathing under water. We already know that a person cannot use the dissolved oxygen in water for breathing, since his lungs only need gaseous oxygen.

To ensure the vital functions of the body under water, it is necessary to systematically deliver the breathing mixture to the lungs.

This can be done in three ways: through a breathing tube, using self-contained breathing apparatus and supplying air from the surface of the water to insulating devices (space suits, bathyscaphes, houses). These paths have their own characteristics. It has long been known that while underwater you can breathe through a snorkel at a depth of no more than 1 m.

At greater depths, the respiratory muscles cannot overcome the additional resistance of the water column, which presses on the chest. Therefore, for swimming underwater, breathing tubes no longer than 0.4 m are used.

But even with such a tube, the breathing resistance is still quite high, moreover, the air entering the inhalation is somewhat depleted in oxygen and has a slight excess of carbon dioxide, which leads to excitation of the respiratory center, expressed in moderate shortness of breath (the respiratory rate increases by 5-7 breaths in a minute).

To ensure normal breathing at depth, it is necessary to supply air to the lungs at a pressure that would correspond to the pressure at a given depth and could balance the external pressure of water on the chest.

In an oxygen suit, the breathing mixture is compressed to the required degree before entering the lungs; in a breathing bag, it is compressed directly by ambient pressure.

In a self-contained compressed air breathing apparatus, this function is performed by a special mechanism. In this case, it is important to observe certain limits of breathing resistance, since a significant amount of it has a negative effect on the human cardiovascular system, causes fatigue of the respiratory muscles, as a result of which the body is not able to maintain the necessary breathing pattern.

In lung-automatic devices, the breathing resistance is still quite high. Its magnitude is estimated because of the effort of the respiratory muscles, which creates a vacuum in the lungs, respiratory tract, inhalation tube and in the submembrane cavity of the pulmonary valve. Under conditions of atmospheric pressure, as well as in a vertical position of a scuba diver in water, when the lung demand valve is at the same level with the “center” of the lungs, the breathing resistance during inhalation is about 50 mm of water. Art. During horizontal swimming with scuba diving, the lung demand valve of which is located behind the back on cylinders, the difference between the water pressure on the lung demand valve membrane and on the scuba diver’s chest is about 300 mm of water. Art.

Therefore, the inhalation resistance reaches 350 mm of water. Art. To reduce breathing resistance, the second stage of reduction in new types of scuba gear is placed in the mouthpiece.

In ventilated equipment, where air is supplied through a hose from the surface, it is compressed using special diving pumps or compressors, and the degree of compression must be proportional to the depth of immersion. The amount of pressure in this case is controlled by a pressure gauge installed between the pump and the diving hose.

SPEARFISHING

Features of breathing under water

We already know that the dissolved oxygen present in water cannot be used by humans for breathing, since the lungs only need gaseous oxygen. To ensure the vital functions of the body under water, it is necessary to systematically deliver a sufficient amount of oxygen to the lungs. This can be done in the following ways:

Through a breathing tube;

Using self-contained breathing apparatus;

Supply from the surface of the water into spacesuits, bathyscaphes, Cousteau-type houses, etc.;

By regeneration (restoration) in submarines.

All these paths are not natural for humans and have their own characteristics.

Breathing through a tube. It is known that while under water at a depth of no more than a meter, you can breathe through a snorkel. At greater depths, the respiratory muscles, as we know, cannot overcome the additional resistance that is formed both during inhalation and exhalation. In practice, for swimming underwater, breathing tubes no longer than 0.4 m are used.

Breathing in self-contained devices. To ensure normal breathing at a significant depth, it is necessary to supply air to the lungs at a pressure that could balance the external pressure of water on the chest.

In an oxygen suit, the breathing mixture is compressed to the required degree in the breathing bag directly by ambient pressure before entering the lungs.

In a self-contained compressed air breathing apparatus, this function is performed by a lung demand valve.

In this case, it is especially important to observe certain limits of breathing resistance, since a significant amount of it has a negative effect on the human cardiovascular system, causes fatigue of the respiratory muscles, as a result of which the body is not able to maintain the necessary breathing pattern.

In lung-automatic devices, the breathing resistance is still quite high. Its value is estimated by the maximum vacuum in the gas-conducting system of the apparatus near the mouthpiece, i.e. in the immediate vicinity of the person’s mouth.

In domestic scuba gear in air it is insignificant and equal to approximately 40-60 mm of water. Art. However, under water, the resistance, especially at the beginning of inspiration, increases significantly and reaches 200-330 mm of water. Art. (with the swimmer in a horizontal position).

Breathing resistance depends on:

a) on the location of the pulmonary valve in relation to the human lungs;

b) on the amount of mechanical resistance of the machine, which is overcome by the respiratory muscles. This is the force of springs, back pressure on valves, friction force in axial joints, etc.;

c) on the length of the inlet and outlet hoses, the nature of their inner surface, the size of the mouthpiece box and the presence of valves in it.

Of the total breathing resistance, the largest part is resistance that depends on the location of the pulmonary valve, i.e., on the difference in pressure on the valve membrane and the chest. To reduce this difference, the lung demand valve is placed in front, at the level of the swimmer's chest, on the stomach and near the mouthpiece box.

Currently, there are also designs of lung demand valves in which a decrease in the amount of breathing resistance is achieved by various types of compensation devices, reducing the volume of the lung demand valve chamber and hoses.

Even a short-term stay under water requires both special technical equipment and appropriate human training. The greatest difficulties in underwater work are associated with providing the diver with a breathing mixture.

The fact is that the gas mixture must enter the diver’s lungs under the same pressure that the water column creates at a given depth. If this ratio is violated, external pressure will simply compress the chest, preventing you from inhaling. With this type of breathing, the work of the respiratory muscles sharply increases. This is why experienced divers breathe deeply but slowly. Some of them take only 3-4 breaths per minute, each time taking 2–2.5 liters of air into the lungs.

The composition of the breathing mixture is also of great importance for deep-sea diving. If you use compressed air to breathe underwater, the partial pressure of oxygen will increase as you dive and at a depth of 90 m will exceed normal by 10 times. At a depth of 40 m, the diver receives a mixture containing 5% oxygen, and at a depth of 100 meters - only 2% (instead of the usual 20.9%). With prolonged inhalation of both pure oxygen and under a pressure of about 3 atm. , dysfunction of the nervous system may occur in the form of a convulsive attack.

The partial pressure of nitrogen in the respiratory mixture is also important to the body. In our usual atmosphere, where nitrogen makes up almost 79%, this gas is a simple diluent of oxygen and does not participate in any processes occurring in the body. However, at high pressure, nitrogen becomes an insidious enemy. It causes a narcotic state similar to alcohol intoxication. Therefore, starting from a depth of 60 m, divers are supplied with nitrogen - an oxygen mixture, where nitrogen is partially or completely replaced by helium, which is not physiologically active.

For normal human life, as well as the vast majority of living organisms, oxygen is necessary. As a result of metabolism, oxygen bonds with carbon atoms to form carbon dioxide (carbon dioxide). The set of processes that ensure the exchange of these gases between the body and the environment is called respiration.

Oxygen entering the human body and the removal of carbon dioxide from the body is ensured by the respiratory system. It consists of the airways and lungs. The upper respiratory tract includes the nasal passages, pharynx and larynx. Then the air enters the trachea, which is divided into two main bronchi. The bronchi, constantly bifurcating and thinning, form the so-called bronchial tree of the lungs. Each bronchiole (the thinnest branches of the bronchi) ends in alveoli, in which gas exchange occurs between air and blood. The total number of alveoli in humans is approximately 700 million, and their total surface is 90-100 m2.

The structure of the respiratory organs.

The surface of the respiratory tract, except for the surface of the alveoli, is impermeable to gases, therefore the space inside the airways is called dead space. Its volume in men is on average about 150 ml, in women - 100 ml.

Air enters the lungs due to the negative pressure created when they are stretched by the diaphragm and intercostal muscles during inhalation. During normal breathing, only inhalation is active; exhalation occurs passively, due to the relaxation of the muscles that provide inhalation. Only with forced breathing are the exhalation muscles activated, which, as a result of additional compression of the chest, ensures a maximum reduction in lung volume.

Breathing process

The frequency and depth of breathing depend on physical activity. Thus, at rest, an adult performs 12-24 respiratory cycles, providing ventilation of the lungs within 6-10 l/min. When performing heavy work, the respiratory rate can increase to 60 cycles per minute, and the amount of pulmonary ventilation can reach 50-100 l/min. The depth of breathing (or tidal volume) during quiet breathing is usually a small part of the total lung capacity. As pulmonary ventilation increases, tidal volume may increase due to inspiratory and expiratory reserve volume. If we fix the difference between the deepest inhalation and the maximum exhalation, we obtain the value of the vital capacity of the lungs (VC), which does not include only the residual volume, which is removed only when the lungs completely collapse.

Regulation of the frequency and depth of breathing occurs reflexively and depends on the amount of carbon dioxide, oxygen in the blood and blood pH. The main stimulus that controls the breathing process is the level of carbon dioxide in the blood (the blood pH value is also associated with this parameter): the higher the CO2 concentration, the greater the pulmonary ventilation. A decrease in the amount of oxygen affects ventilation to a lesser extent. This is due to the specificity of oxygen binding to hemoglobin in the blood. A significant compensatory increase in pulmonary ventilation occurs only after the partial pressure of oxygen in the blood drops below 12-10 kPa.

How does diving under water affect the breathing process?? Let's first consider the situation of snorkeling. Breathing through the tube becomes significantly more difficult even when diving a few centimeters. This occurs due to the fact that breathing resistance increases: firstly, when diving, the dead space increases by the volume of the breathing tube, and secondly, in order to inhale, the respiratory muscles are forced to overcome increased hydrostatic pressure. At a depth of 1 m, a person can breathe through a tube for no more than 30 seconds, and at greater depths breathing is almost impossible, primarily due to the fact that the respiratory muscles cannot overcome the pressure of the water column in order to inhale from the surface. Breathing tubes with a length of 30-37 cm are considered optimal. Using longer breathing tubes can lead to disturbances in the functioning of the heart and lungs.

Another important characteristic that affects breathing is the diameter of the tube. With a small diameter of the tube, not enough air flows in, especially if there is a need to perform any work (for example, swimming quickly), and with a large diameter, the volume of dead space increases significantly, which also makes breathing very difficult. The optimal tube diameter is 18-20 mm. Using a tube that is not standard in length or diameter may result in involuntary hyperventilation.

When swimming in self-contained breathing apparatus the main difficulties in breathing are also associated with increased resistance to inhalation and exhalation. The distance between the so-called center of pressure and the breathing machine box has the least effect on increasing breathing resistance. The "center of pressure" was established by Jarrett in 1965. It is 19 cm below and 7 cm posterior to the jugular cavity. When developing various models of breathing apparatus, it is always taken into account and the breathing machine box is placed as close as possible to this point. The second factor influencing the increase in breathing resistance is the amount of additional dead space. It is especially large in devices with thick corrugated tubes. The total resistance of various valves, membranes and springs in the system for reducing the pressure of the breathing mixture also plays an important role. And the last factor is the increase in gas density due to increasing pressure with increasing depth.

In modern models of regulators, designers strive to minimize the effects of increasing breathing resistance, creating so-called balanced breathing machines. But amateur submariners still have quite a lot of old-model devices with increased breathing resistance. Such devices, in particular, are the legendary AVM-1 and AVM-1m. Breathing in these devices leads to high energy consumption, so it is not recommended to perform heavy physical work in them and make long dives to depths of over 20 m.

The optimal type of breathing when swimming with a self-contained breathing apparatus should be considered slower and deeper breathing. The recommended frequency is 14-17 breaths per minute. With this type of breathing, sufficient gas exchange is ensured with minimal work of the respiratory muscles, and the activity of the cardiovascular system is facilitated. Frequent breathing makes it difficult for the heart to work and leads to its overload.

Affects the functioning of the respiratory system and the rate of immersion in depth. With a rapid increase in pressure (compression), the vital capacity of the lungs decreases; with a slow increase, it remains virtually unchanged. The decrease in vital capacity is due to several reasons. Firstly, when diving into depth, to compensate for external pressure, an additional volume of blood rushes into the lungs and, apparently, with rapid compression, some bronchioles are compressed by “swollen” blood vessels; This effect is combined with a rapid increase in gas density, and as a result, air is blocked in some areas of the lungs ( "air traps" appear»). « Air traps" are extremely dangerous, as they significantly increase the risk of lung barotrauma both during continued immersion and during ascent, especially if the ascent mode and speed are not observed. Most often, such “traps” are formed by divers who are underwater in a vertical position. There is one more nuance associated with the vertical position of the diver. This is the heterogeneity of gas exchange in a vertical position: under the influence of gravity, blood enters the lower parts of the lungs, and the gas mixture accumulates in the upper parts, depleted of blood. If the diver is underwater in a horizontal position, face down, the relative value of alveolar ventilation increases significantly, compared with his vertical position, gas exchange and oxygen saturation of arterial blood improves.

During the period of decompression and some time after it, vital capacity also appears to be reduced due to increased blood flow into the lungs.

Negatively affects the respiratory system There is also the fact that the air coming from the cylinders is usually cold and contains virtually no moisture. Inhalation of cold gas can cause breathing problems, manifested by trembling of the respiratory muscles, pain in the chest, increased secretion of the mucous membranes of the nose, trachea and bronchi, and difficulty breathing. When swimming in cold water, the problem of mucus secretion becomes especially acute: swallowing movements, necessary to equalize the pressure in the middle ear cavity, become difficult. And due to the fact that the incoming air contains practically no moisture, irritation of the mucous membranes of the eyes, nose, trachea, and bronchi can develop. An aggravating factor here is also cooling the body.

As you ascend into the mountains, the oxygen pressure in the air steadily decreases, which leads to a drop in this pressure in the alveoli and, as a consequence, to a drop in oxygen tension in the blood. If the oxygen tension drops below 50-60 mmHg, the oxygen saturation of hemoglobin begins to decrease very quickly.

Characteristics of physiological changes during breathing in the mountains

Most people do not experience problems breathing in the mountains up to an altitude of 2.5 km. This does not mean that at an altitude of 2 km the body is in the same state as at barometric pressure at sea level. Although at an altitude of up to 3 km the blood is saturated with oxygen to no less than 90% of its capacity, the tension of oxygen dissolved in the blood is already reduced here and this explains a number of observed shifts in breathing in the mountains. These include:

• deepening and slight increase in breathing;
• increased heart rate and increased minute volume;
• slight increase in BCC;
• increased new formation of red blood cells;
• a small drop in receptor excitability, detectable only by very subtle methods, which disappears after two or three days at the specified altitude.

All these changes during breathing in the mountains in a healthy person, however, are precisely regulatory processes, the normal course of which ensures performance at altitude. It is not for nothing that staying at an altitude of 1-2 km is sometimes used as a therapeutic technique in the fight against certain diseases.

From a height of 3 km, and in a number of people (in the absence of muscular work) only from a height of 3.5 km, various disorders begin to be detected, which mainly depend on changes in the activity of higher centers. When breathing in the mountains, the tension of oxygen dissolved in the blood decreases, and the amount of oxygen bound by hemoglobin also decreases. Symptoms of respiratory hypoxia occur when blood oxygen saturation falls below 85% of the oxygen capacity of the blood. If oxygen saturation during respiratory hypoxia falls below 50-45% of oxygen capacity, then death occurs in a person.

When the rise to a significant height occurs slowly (for example, when climbing), symptoms of hypoxia develop, which are not detected during rapidly developing hypoxia, leading to loss of consciousness. In this case, due to a disorder of higher nervous activity, fatigue, drowsiness, trembling, shortness of breath, palpitations, often nausea, and sometimes bleeding are noted (altitude sickness or mountain sickness).

Changes in nervous activity can begin even before the amount of oxyhemoglobin in the blood decreases, depending on the decrease in oxygen tension dissolved in the blood. In dogs, some changes in nervous activity are sometimes observed already at 1000 m, first expressed in an increase in conditioned reflexes and a weakening of inhibitory processes in the cerebral cortex. At higher altitudes, conditioned reflexes decrease and then (at an altitude of 6-8 km) disappear. Unconditioned reflexes also decrease. Inhibition increases in the cerebral cortex. If at low altitudes (2-4 km) changes in conditioned reflexes are noted only at first, then at significant altitudes the disturbances in conditioned reflex activity do not decrease with continued hypoxia, but rather deepen.

Changes in the state of the cerebral cortex caused by hypoxia from breathing in the mountains, of course, affect the course of all physiological functions. Inhibition developing in the cortex can also transfer to subcortical formations, which affects both the disruption of motor acts and the strengthening of reflexes to impulses from interoceptors.

Height limit

Depending on individual characteristics and training, the altitude at which breathing disorders occur in the mountains may be different, but these disorders, although at different altitudes, necessarily occur in everyone.

For healthy people, we can indicate on average the following scale of heights, where certain functional changes in the body occur:

• up to an altitude of 2.5 km, most people (and some people up to an altitude of 3.5-4 km) do not experience significant distress. The saturation of the blood with oxygen here is even higher than 85% of the oxygen capacity, and the changes in the state of the body are characterized only by increased activity of the respiratory and cardiovascular systems, as well as increased new formation of red blood cells;
• at an altitude of 4-5 km, disorders of higher nervous activity, regulation of breathing, and blood circulation begin to be noted (euphoria or heavy health, easy fatigue, Cheyne-Stokes breathing, a sharp increase in heart rate, sometimes collapse);
• at an altitude of 6-7 km these symptoms become very serious for most people, with the exception of those specially trained;
• breathing in the mountains at an altitude of 7-8 km always leads to a serious condition and is dangerous for most people, and an altitude of 8.5 km is the limit above which a person cannot rise without inhaling oxygen.

In animals that constantly live in the mountains, there is a significant undersaturation of the blood with oxygen. For example, in sheep at an altitude of 4000 m, blood oxygen saturation is only about 65% of oxygen capacity, but there are no pathological symptoms of hypoxemia.