Partial pressure of oxygen in water. What is partial pressure of oxygen. Diving underwater

The meaning of breathing

Breathing is a vital process of constant exchange of gases between the body and its surrounding environment. In the process of breathing, a person absorbs oxygen from the environment and releases carbon dioxide.

Almost all complex reactions of transformation of substances in the body require the participation of oxygen. Without oxygen, metabolism is impossible, and a constant supply of oxygen is necessary to preserve life. In cells and tissues, as a result of metabolism, carbon dioxide is formed, which must be removed from the body. The accumulation of significant amounts of carbon dioxide inside the body is dangerous. Carbon dioxide is carried by the blood to the respiratory organs and exhaled. Oxygen entering the respiratory organs during inhalation diffuses into the blood and is delivered to organs and tissues by the blood.

There are no reserves of oxygen in the human and animal bodies, and therefore its continuous supply into the body is a vital necessity. If a person, in necessary cases, can live without food for more than a month, without water for up to 10 days, then in the absence of oxygen, irreversible changes occur within 5-7 minutes.

Composition of inhaled, exhaled and alveolar air

By alternately inhaling and exhaling, a person ventilates the lungs, maintaining a relatively constant gas composition in the pulmonary vesicles (alveoli). A person breathes atmospheric air with a high content of oxygen (20.9%) and a low content of carbon dioxide (0.03%), and exhales air in which there is 16.3% oxygen and 4% carbon dioxide (Table 8).

The composition of alveolar air differs significantly from the composition of atmospheric, inhaled air. It contains less oxygen (14.2%) and a large amount of carbon dioxide (5.2%).

Nitrogen and inert gases that make up the air do not take part in respiration, and their content in inhaled, exhaled and alveolar air is almost the same.

Why does exhaled air contain more oxygen than alveolar air? This is explained by the fact that when you exhale, air that is in the respiratory organs, in the airways, is mixed with the alveolar air.

Partial pressure and tension of gases

In the lungs, oxygen from the alveolar air passes into the blood, and carbon dioxide from the blood enters the lungs. The transition of gases from air to liquid and from liquid to air occurs due to the difference in the partial pressure of these gases in air and liquid. Partial pressure is the part of the total pressure that accounts for the share of a given gas in a gas mixture. The higher the percentage of gas in the mixture, the correspondingly higher its partial pressure. Atmospheric air, as is known, is a mixture of gases. Atmospheric air pressure 760 mm Hg. Art. The partial pressure of oxygen in atmospheric air is 20.94% of 760 mm, i.e. 159 mm; nitrogen - 79.03% of 760 mm, i.e. about 600 mm; There is little carbon dioxide in the atmospheric air - 0.03%, therefore its partial pressure is 0.03% of 760 mm - 0.2 mm Hg. Art.

For gases dissolved in a liquid, the term “voltage” is used, corresponding to the term “partial pressure” used for free gases. Gas tension is expressed in the same units as pressure (mmHg). If the partial pressure of a gas in the environment is higher than the voltage of that gas in the liquid, then the gas dissolves in the liquid.

The partial pressure of oxygen in the alveolar air is 100-105 mm Hg. Art., and in the blood flowing to the lungs the oxygen tension is on average 60 mm Hg. Art., therefore, in the lungs, oxygen from the alveolar air passes into the blood.

The movement of gases occurs according to the laws of diffusion, according to which gas spreads from a medium with high partial pressure to a medium with lower pressure.

Gas exchange in the lungs

The transition of oxygen from the alveolar air into the blood in the lungs and the flow of carbon dioxide from the blood into the lungs obey the laws described above.

Thanks to the work of the great Russian physiologist Ivan Mikhailovich Sechenov, it became possible to study the gas composition of the blood and the conditions of gas exchange in the lungs and tissues.

Gas exchange in the lungs occurs between alveolar air and blood by diffusion. The alveoli of the lungs are intertwined with a dense network of capillaries. The walls of the alveoli and capillaries are very thin, which facilitates the penetration of gases from the lungs into the blood and vice versa. Gas exchange depends on the size of the surface through which gases diffuse and the difference in partial pressure (tension) of the diffusing gases. With a deep breath, the alveoli stretch, and their surface reaches 100-105 m2. The surface area of ​​the capillaries in the lungs is also large. There is, and a sufficient, difference between the partial pressure of gases in the alveolar air and the tension of these gases in the venous blood (Table 9).

From Table 9 it follows that the difference between the tension of gases in the venous blood and their partial pressure in the alveolar air is 110 - 40 = 70 mm Hg for oxygen. Art., and for carbon dioxide 47 - 40 = 7 mm Hg. Art.

Experimentally, it was possible to establish that with a difference in oxygen tension of 1 mm Hg. Art. in an adult at rest, 25-60 ml of oxygen can enter the blood in 1 minute. A person at rest needs approximately 25-30 ml of oxygen per minute. Therefore, an oxygen pressure difference of 70 mmHg. Art. is sufficient to provide the body with oxygen under different conditions of its activity: during physical work, sports exercises, etc.

The rate of diffusion of carbon dioxide from the blood is 25 times greater than that of oxygen, therefore, with a pressure difference of 7 mm Hg. Art., carbon dioxide has time to be released from the blood.

Transfer of gases by blood

Blood carries oxygen and carbon dioxide. In blood, as in any liquid, gases can be in two states: physically dissolved and chemically bound. Both oxygen and carbon dioxide dissolve in very small quantities in the blood plasma. Most oxygen and carbon dioxide are transported in chemically bound form.

The main carrier of oxygen is hemoglobin in the blood. 1 g of hemoglobin binds 1.34 ml of oxygen. Hemoglobin has the ability to combine with oxygen, forming oxyhemoglobin. The higher the partial pressure of oxygen, the more oxyhemoglobin is formed. In the alveolar air, the partial pressure of oxygen is 100-110 mm Hg. Art. Under such conditions, 97% of blood hemoglobin binds to oxygen. Blood brings oxygen to tissues in the form of oxyhemoglobin. Here the partial pressure of oxygen is low, and oxyhemoglobin - a fragile compound - releases oxygen, which is used by the tissues. The binding of oxygen by hemoglobin is also influenced by carbon dioxide tension. Carbon dioxide reduces the ability of hemoglobin to bind oxygen and promotes the dissociation of oxyhemoglobin. Increasing temperature also reduces the ability of hemoglobin to bind oxygen. It is known that the temperature in the tissues is higher than in the lungs. All these conditions help dissociate oxyhemoglobin, as a result of which the blood releases the oxygen released from the chemical compound into the tissue fluid.

The property of hemoglobin to bind oxygen is vital for the body. Sometimes people die from lack of oxygen in the body, surrounded by the cleanest air. This can happen to a person who finds himself in low pressure conditions (at high altitudes), where the thin atmosphere has a very low partial pressure of oxygen. On April 15, 1875, the Zenit balloon, with three balloonists on board, reached an altitude of 8000 m. When the balloon landed, only one person remained alive. The cause of death was a sharp decrease in the partial pressure of oxygen at high altitude. At high altitudes (7-8 km), arterial blood in its gas composition approaches venous blood; all tissues of the body begin to experience an acute lack of oxygen, which leads to serious consequences. Climbing to altitudes above 5000 m usually requires the use of special oxygen devices.

With special training, the body can adapt to the low oxygen content in the atmospheric air. A trained person’s breathing deepens, the number of red blood cells in the blood increases due to their increased formation in the hematopoietic organs and their supply from the blood depot. In addition, heart contractions increase, which leads to an increase in minute blood volume.

Pressure chambers are widely used for training.

Carbon dioxide is carried by the blood in the form of chemical compounds - sodium and potassium bicarbonates. The binding of carbon dioxide and its release into the blood depend on its tension in the tissues and blood.

In addition, blood hemoglobin is involved in the transfer of carbon dioxide. In tissue capillaries, hemoglobin enters into a chemical combination with carbon dioxide. In the lungs, this compound breaks down to release carbon dioxide. About 25-30% of the carbon dioxide released in the lungs is carried by hemoglobin.

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Hypoxia is most clearly detected during stay in a rarefied space, when the partial pressure of oxygen drops.

In an experiment, oxygen starvation can occur at relatively normal atmospheric pressure, but with a low oxygen content in the surrounding atmosphere, for example, when an animal is in a confined space with a low oxygen content. The phenomena of oxygen starvation can be observed when climbing mountains, rising in an airplane to a high altitude - mountain and altitude sickness(Fig. 116).

The first signs of acute mountain sickness can often be observed already at an altitude of 2500 - 3000 m. For most people, they appear when climbing to 4000 m and above. The partial pressure of oxygen in the air, equal (at atmospheric pressure 760 mm Hg) to 159 mm, drops at this altitude (430 mm atmospheric pressure) to 89 mm. At the same time, arterial blood oxygen saturation begins to decrease. Symptoms of hypoxia usually appear when arterial oxygen saturation is around 85%, and death can occur when arterial oxygen saturation falls below 50%.

Climbing a mountain is accompanied by characteristic phenomena also due to temperature conditions, wind and muscle activity performed during the ascent. The more the metabolism increases due to muscle tension or a decrease in air temperature, the sooner signs of illness appear.

Disorders that arise during ascent to altitude develop more strongly the faster the ascent occurs. Training is of great importance in this regard.

Oxygen starvation when ascending in an airplane to a high altitude has some peculiarities. Climbing the mountain is slow and requires intense muscle work. Airplanes can reach altitude within a very short time. A pilot's stay at an altitude of 5000 m in the absence of sufficient training is accompanied by sensations of headache, dizziness, heaviness in the chest, palpitations, expansion of gases in the intestines, as a result of which the diaphragm is pushed upward, and breathing becomes even more difficult. The use of oxygen devices eliminates many of these phenomena (Fig. 117).

The effect on the body of low oxygen content in the air is expressed in disorders of the nervous system, breathing and circulation.

Some excitement is followed by fatigue, apathy, drowsiness, heaviness in the head, mental disorders in the form of irritability followed by depression, some loss of orientation, motor function disorders, and disorders of higher nervous activity. At medium altitudes, a weakening of internal inhibition develops in the cerebral cortex, and at higher altitudes, diffuse inhibition develops. Disorders of autonomic functions also develop in the form of shortness of breath, increased heart activity, changes in blood circulation and digestive disorders.

With acute oxygen starvation, the breath. It becomes superficial and frequent, which is the result of stimulation of the respiratory center. Sometimes a peculiar, intermittent, so-called periodic breathing (Cheyne-Stokes type) occurs. In this case, pulmonary ventilation noticeably suffers. With the gradual onset of oxygen starvation, breathing becomes frequent and deep, air circulation in the alveoli improves noticeably, but the carbon dioxide content and its tension in the alveolar air drop, i.e., hypocapnia develops, complicating the course of hypoxia. Impaired breathing may cause loss of consciousness.

Acceleration and intensification of the activity of the heart arise due to an increase in the function of its accelerating and amplifying nerves, as well as a decrease in the function of the vagus nerves. Therefore, increased heart rate during oxygen starvation is one of the indicators of the reaction of the nervous system that regulates blood circulation.

At high altitudes, a number of other circulatory disorders also occur. Blood pressure initially increases, but then begins to decrease in accordance with the state of the vasomotor centers. With a sharp decrease in the oxygen content in the inhaled air (up to 7 - 6%), the activity of the heart noticeably weakens, blood pressure drops, and venous pressure rises, cyanosis and arrhythmia develop.

Sometimes it is also observed bleeding from the mucous membranes of the nose, mouth, conjunctiva, respiratory tract, and gastrointestinal tract. Great importance in the occurrence of such bleeding is attached to the expansion of superficial blood vessels and disruption of their permeability. These changes occur partly due to the action of toxic metabolic products on the capillaries.

Dysfunction of the nervous system from being in a rarefied space also manifests itself gastrointestinal disorders usually in the form of lack of appetite, inhibition of the digestive glands, diarrhea and vomiting.

During high altitude hypoxia, the metabolism. Oxygen consumption initially increases, and then, with severe oxygen starvation, it decreases, the specific dynamic effect of protein decreases, and the nitrogen balance becomes negative. Residual nitrogen in the blood increases, ketone bodies accumulate, especially acetone, which is excreted in the urine.

A decrease in the oxygen content in the air to a certain limit has little effect on the formation of oxyhemoglobin. However, later, when the oxygen content in the air decreases to 12%, the oxygen saturation of the blood becomes about 75%, and when the oxygen content in the air is 6 - 7%, it is 50 - 35% of normal. The oxygen tension in capillary blood is especially reduced, which significantly affects its diffusion into the tissue.

Increased pulmonary ventilation and an increase in the tidal volume of the lungs during hypoxia cause depletion of alveolar air and blood in carbon dioxide (hypocapnia) and the occurrence of relative alkalosis, as a result of which the excitability of the respiratory center can be temporarily inhibited and the activity of the heart is weakened. Therefore, inhalation of carbon dioxide at altitudes, causing an increase in the excitability of the respiratory center, helps to increase the oxygen content in the blood and thereby improves the condition of the body.

However, the continuing decrease in the partial pressure of oxygen during ascent to altitude contributes to the further development of hypoxemia and hypoxia. The phenomena of insufficiency of oxidative processes are increasing. Alkalosis is again replaced by acidosis, which is again somewhat weakened due to an increase in the respiratory rate, a decrease in oxidative processes and the partial pressure of carbon dioxide.

Noticeably changed when rising to altitude and heat exchange. Heat transfer at high altitude increases mainly due to the evaporation of water by the surface of the body and through the lungs. Heat production gradually lags behind heat loss, as a result of which body temperature, which initially increases slightly, then decreases.

The onset of signs of oxygen starvation largely depends on the characteristics of the body, the state of its nervous system, lungs, heart and blood vessels, which determine the body’s ability to tolerate a rarefied atmosphere.

The nature of the action of rarefied air also depends on the rate of development of oxygen starvation. In acute oxygen starvation, dysfunction of the nervous system comes to the fore, while in chronic oxygen starvation, due to the gradual development of compensatory processes, pathological phenomena from the nervous system are not detected for a long time.

A healthy person generally copes satisfactorily with lowering barometric pressure and partial pressure of oxygen to a certain limit, and the better the slower the ascent and the easier the body adapts. The limit for a person can be considered a decrease in atmospheric pressure to one third of normal, i.e., up to 250 mm Hg. Art., which corresponds to an altitude of 8000 - 8500 m and an oxygen content in the air of 4 - 5%.

It has been established that during stay at heights there occurs device body, or its acclimatization, providing compensation for breathing disorders. Residents of mountainous areas and trained climbers may not develop mountain sickness when climbing to an altitude of 4000 - 5000 m. Highly trained pilots can fly without an oxygen apparatus at an altitude of 6000 - 7000 m and even higher.

The main air parameters that determine the physiological state of a person are:

absolute pressure;

oxygen percentage;

temperature;

relative humidity;

harmful impurities.

Of all the listed air parameters, absolute pressure and oxygen percentage are crucial for humans. Absolute pressure determines the partial pressure of oxygen.

The partial pressure of any gas in a gas mixture is the portion of the total pressure of the gas mixture that is attributable to that gas in accordance with its percentage content.

So for the partial pressure of oxygen we have

Where
− percentage of oxygen in the air (
);

R H − air pressure at altitude N;

−partial pressure of water vapor in the lungs (back pressure for breathing
).

The partial pressure of oxygen is of particular importance for the physiological state of a person, since it determines the process of gas exchange in the body.

Oxygen, like any gas, tends to move from a space in which its partial pressure is greater to a space with less pressure. Consequently, the process of saturating the body with oxygen occurs only in the case when the partial pressure of oxygen in the lungs (in the alveolar air) is greater than the partial pressure of oxygen in the blood flowing to the alveoli, and this latter will be greater than the partial pressure of oxygen in the tissues of the body.

To remove carbon dioxide from the body, it is necessary to have a ratio of its partial pressures opposite to that described, i.e. The highest value of the partial pressure of carbon dioxide should be in the tissues, less in the venous blood and even less in the alveolar air.

At sea level at R H= 760 mm Hg. Art. the partial pressure of oxygen is ≈150 mmHg. Art. With this
ensures normal saturation of human blood with oxygen during breathing. As the flight altitude increases
decreases due to decrease P H(Fig. 1).

Special physiological studies have established that the minimum partial pressure of oxygen in the inhaled air
This figure is usually called physiological limit of a person’s stay in an open cabin in size
.

Partial pressure of oxygen 98 mm Hg. Art. corresponds to height N= 3 km. At
< 98 mmHg Art. Possible impairment of vision, hearing, slow reaction and loss of consciousness.

To prevent these phenomena, aircraft use oxygen supply systems (OSS), providing
> 98 mmHg Art. in inhaled air in all flight modes and in emergency situations.

Practically in aviation the altitude is accepted N = 4 km as the limit for flights without oxygen devices, that is, aircraft with a service ceiling of less than 4 km may not have a flight control system.

1. Partial pressure of oxygen and carbon dioxide in the human body under terrestrial conditions

When changing the values ​​specified in the table
And
Normal gas exchange in the lungs and throughout the human body is disrupted.

1.8 Partial tension of oxygen in the blood

PaO2 is the partial tension of oxygen in arterial blood. This is the tension of physically distributed oxygen in arterial blood plasma under the influence of a partial pressure equal to 100 mm Hg (PaO2 = 100 mm Hg). Every 100 ml of plasma contains 0.3 ml of oxygen. The O2 content in the arterial blood of trained athletes under resting conditions does not differ from its content in non-athletes. During physical activity, an accelerated breakdown of oxyhemoglobin occurs in the arterial blood flowing to the muscles with the release of free O2, so PaO2 increases

PвO2 is the partial tension of oxygen in venous blood. This is the tension of physically dissolved oxygen in the plasma of venous blood flowing from the tissue (muscle). Characterizes the tissue's ability to utilize oxygen. At rest it is 40-50 mm Hg. At maximum work, due to intensive utilization of O2 by working muscles, it decreases to 10-20 mmHg. Art.

The difference between PaO2 and PvO2 is the value of ABP-O2 - the arterial-venous difference in oxygen. Characterizes the tissue's ability to utilize oxygen. ABP-O2 is the difference between the oxygen content in arterial blood released into the systemic arteries from the left ventricle and in venous blood flowing to the right atrium.

With the development of aerobic endurance, pronounced sarcoplasmic hypertrophy of skeletal muscles occurs, which leads to a decrease in oxygen in the venous blood (PbO2), and a corresponding increase in ABP-O2. So, if at rest PbO2 in men and women is 30 mm Hg, then after endurance exercise in untrained men PbO2 = 13 mm Hg, in untrained women 14 mm Hg. Accordingly, in trained men and women - 10 and 11 mm Hg. In women, the content of hemoglobin, bcc and oxygen content in arterial blood is lower, therefore, with equal oxygen content in venous blood, the total systemic AVR-O2 in women is less. At rest, it is equal to 5.8 ml of O2 per 100 ml of blood, versus 6.5 in men. After completing the exercise, untrained women had ABP-O2 = 11.1 ml O2/100 ml of blood, versus 14 in untrained men. As a result of training, ABP-O2 increases in both women and men as a result of a decrease in the oxygen content in the venous blood (12.8 and 15.5, respectively).

According to Fick's formula (PO2(MPC) = SV*ABP-O2), the product of SV by ABP-O2 determines the maximum oxygen consumption and is an important indicator of aerobic endurance. Endurance athletes use their oxygen transport capabilities more efficiently because they use more oxygen contained in each milliliter of blood than untrained people.

1.9 The influence of health training on the hemodynamics of the body

As a result of health training, the functionality of the cardiovascular system increases. There is an economization of the work of the heart at rest and an increase in the reserve capabilities of the circulatory apparatus during muscle activity. One of the most important effects of physical training is a decrease in heart rate at rest (bradycardia) as a manifestation of economization of cardiac activity and lower myocardial oxygen demand. Increasing the duration of the diastole (relaxation) phase provides greater blood flow and a better supply of oxygen to the heart muscle. In people with bradycardia, cases of coronary heart disease (CHD) are detected much less frequently than in people with a rapid pulse. It is believed that an increase in heart rate at rest by 15 beats/min increases the risk of sudden death from a heart attack by 70%. The same pattern is observed with muscle activity.

When performing a standard load on a bicycle ergometer in trained men, the volume of coronary blood flow is almost 2 times less than in untrained men (140 versus 260 ml/min per 100 g of myocardial tissue), and the myocardial oxygen demand is correspondingly 2 times less (20 versus 40 ml /min per 100g tissue). Thus, with an increase in the level of training, the myocardial oxygen demand decreases both at rest and at submaximal loads, which indicates economization of cardiac activity. As training increases and myocardial oxygen demand decreases, the level of threshold load that the subject can perform without the threat of myocardial ischemia and an attack of angina increases.

The most pronounced increase in the reserve capabilities of the circulatory system during intense muscular activity is: an increase in maximum heart rate, CO and MV, ABP-O2, a decrease in total peripheral vascular resistance, which facilitates the mechanical work of the heart and increases its productivity. Adaptation of the peripheral blood circulation comes down to an increase in muscle blood flow under extreme loads (maximum 100 times), an arteriovenous difference in oxygen, the density of the capillary bed in working muscles, an increase in the concentration of myoglobin and an increase in the activity of oxidative enzymes.

An increase in fibrinolytic activity of the blood during health-improving training (maximum 6 times) and a decrease in the tone of the sympathetic nervous system also play a protective role in the prevention of cardiovascular diseases. As a result, the response to neurohormones decreases under conditions of emotional stress, i.e. The body's resistance to stress increases.

In addition to the pronounced increase in the body's reserve capabilities under the influence of health-improving training, its preventive effect is also extremely important. With increasing training (as the level of physical performance increases), there is a clear decrease in all the main risk factors: cholesterol in the blood, blood pressure and body weight. There are examples when, as UVC increased, the cholesterol content in the blood decreased from 280 to 210 mg, and triglycerides from 168 to 150 mg%. At any age, with the help of training, you can increase aerobic capacity and the level of endurance - indicators of the biological age of the body and its vitality. For example, well-trained middle-aged runners have a maximum possible heart rate that is about 10 beats per minute higher than untrained runners. Physical exercises such as walking and running (3 hours per week) already after 10-12 weeks lead to an increase in VO2 max by 10-15%.

Thus, the health-improving effect of mass physical education is associated primarily with an increase in the aerobic capabilities of the body, the level of general endurance and physical performance. Increased performance is accompanied by a preventive effect against risk factors for cardiovascular diseases: a decrease in body weight and fat mass, cholesterol and triglycerides in the blood, a decrease in blood pressure and heart rate. In addition, regular physical training can significantly slow down the development of age-related changes in physiological functions, as well as degenerative changes in various organs and systems (including delay and reverse development of atherosclerosis). Performing physical exercises has a positive effect on all parts of the musculoskeletal system, preventing the development of degenerative changes associated with age and physical inactivity. The mineralization of bone tissue and calcium content in the body increases, which prevents the development of osteoporosis. The flow of lymph to the articular cartilage and intervertebral discs increases, which is the best means of preventing arthrosis and osteochondrosis. All these data indicate the invaluable positive impact of health-improving physical education on the human body.

Conclusion

This course work examined the main hemodynamic characteristics and their changes during physical activity. Brief conclusions are summarized in Table 10.

Table10. Basic hemodynamic characteristics

Column 3 provides a brief description of the studied quantities and their limit values.

The degree of change in hemodynamic parameters during physical activity depends on the initial values ​​at rest. Physical activity requires a significant increase in the functions of the cardiovascular, respiratory and circulatory systems. Providing working muscles with a sufficient amount of oxygen and removing carbon dioxide from tissues depends on this. The cardiovascular system has a number of mechanisms that allow it to deliver as much blood as possible to the periphery. First of all, these are hemodynamic factors: an increase in heart rate, CO, blood volume, acceleration of blood flow, changes in blood pressure. These indicators are different for representatives of different sports. (According to sports specialization, sprinters train speed, stayers train endurance, weightlifters train strength.)

The use of echocardiography in sports medicine has made it possible to establish differences in the ways of heart adaptation depending on the direction of the training process. In athletes training endurance, cardiac adaptation occurs primarily due to dilatation with slight hypertrophy, and in athletes training strength - due to true myocardial hypertrophy and slight dilatation. With intense physical work, cardiac activity increases. The heart should be trained gradually according to age.

A hemodynamic factor such as changes in blood pressure is very important. The direction of the training process affects blood pressure. Physical loads of a dynamic nature help to reduce it, while statistical loads help to increase it. Hypertension can be caused by physical and emotional stress. A low level of systolic pressure in the pulmonary artery is an indicator of the high state of the cardiovascular system of endurance athletes. It characterizes the potential readiness of the body, in particular hemodynamics, for large and prolonged physical exertion.

The physiological changes in the body caused by endurance training are the same in women as in men. Thus, in the oxygen transport system, maximum indicators (LVmax, SVmax, COmax), lactate concentration at maximum work increase, and HRmax decreases due to increased parasympathetic influences. All this indicates an increase in efficiency and economy, as well as an increase in the reserve capabilities of the oxygen transport system.

The state of the body, both at rest and during exercise, depends on many reasons: external conditions, specific sports (swimming, winter sports, etc.), hereditary factors, gender, age, etc.

The limit to the growth of training effects in each person is genetically predetermined. Even systematic intense physical training cannot increase the body's functional capabilities beyond the limit determined by the genotype. Resting heart rate, heart size, left ventricular wall thickness, myocardial capillarization, and coronary artery wall thickness are influenced by hereditary factors.

It must be borne in mind that physical exercise helps to improve health, improve the biological mechanisms of protective and adaptive reactions, and increase nonspecific resistance to various harmful environmental influences, only under the obligatory condition that the degree of physical activity in these classes is optimal for this particular person. Only the optimal degree of physical activity, corresponding to the capabilities of the person performing it, ensures improved health, physical improvement, prevents the occurrence of a number of diseases and helps to increase life expectancy. Physical activity less than optimal does not give the desired effect, above optimal it becomes excessive, and excessive activity, instead of a healing effect, can cause various diseases and even sudden death from cardiac overstrain. Sports achievements should increase as a result of improved health.

Special mention should be made of the influence of health-improving physical culture on the aging body. Physical education is the main means of delaying age-related deterioration of physical qualities and a decrease in the adaptive abilities of the body in general and the cardiovascular system in particular. Changes in the circulatory system and a decrease in cardiac performance entail a pronounced decrease in the maximum aerobic capabilities of the body, a decrease in the level of physical performance and endurance. The rate of age-related decrease in MOC in the period from 20 to 65 years in untrained men averages 0.5 ml/min/kg, in women - 0.3 ml/min/kg per year. In the period from 20 to 70 years, maximum aerobic performance decreases by almost 2 times - from 45 to 25 ml/kg (or by 10% per decade). Adequate physical training and health-improving physical education classes can significantly stop age-related changes in various functions. Physical labor, physical education and outdoor sports are especially beneficial, while smoking and alcohol abuse are especially harmful to the cardiovascular system.

The above material traces the patterns of changes in the basic hemodynamic characteristics of the body. Simultaneously increasing the level of health and functional state of a person is impossible without the active, widespread and comprehensive use of physical education and sports.

Literature

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...) and relative (with significant dilatation of the left ventricle with expansion of the aortic opening) insufficiency of the aortic valve. Etiology 1) RL; 2) FROM; 3) syphilitic aortitis; 4) diffuse connective tissue diseases; 5) atherosclerosis of the aorta; 6) injuries; 7) congenital defect. Pathogenesis and changes in hemodynamics. The main pathological process leads to wrinkling (rheumatism, ...

Literary data on the issue being studied; 2) assess morphofunctional indicators in participants of groups of various training orientations at the initial stage; 3) determine the influence of aerobic and anaerobic physical exercises on the morphofunctional capabilities of those involved; 4) conduct a comparative analysis of the indicators studied among group participants in the dynamics of the training process. 2.2...

We did not find an electrocardiographic technique mainly for identifying physiological and pathological changes in the heart, while we did not find any work that would use ECG indicators to determine fitness and the effect of physical activity on changes in heart rate and blood pressure.”12 The analysis of the ECG showed , that at rest the studied values ​​are for gymnasts 15-16 years old...

If there is a mixture of gases above the liquid, then each gas dissolves in it according to its partial pressure in the mixture, i.e., the pressure that falls on its share. Partial pressure of any gas in a gas mixture can be calculated by knowing the total pressure of the gas mixture and its percentage composition. So, at an atmospheric air pressure of 700 mm Hg. the partial pressure of oxygen is approximately 21% of 760 mm, i.e. 159 mm, nitrogen - 79% of 700 mm, i.e. 601 mm.

When calculating gas partial pressure in alveolar air, it should be taken into account that it is saturated with water vapor, the partial pressure of which at body temperature is 47 mm Hg. Art. Therefore, the share of the remaining gases (nitrogen, oxygen, carbon dioxide) is no longer 700 mm, but 700-47 - 713 mm. If the oxygen content in the alveolar air is 14.3%, its partial pressure will be only 102 mm; with a carbon dioxide content of 5.6%, its partial pressure is 40 mm.

If a liquid saturated with gas at a certain partial pressure comes into contact with the same gas, but having a lower pressure, then part of the gas will come out of solution and the amount of dissolved gas will decrease. If the gas pressure is higher, then more gas will dissolve in the liquid.

The dissolution of gases depends on partial pressure, i.e. the pressure of a particular gas, and not the total pressure of the gas mixture. Therefore, for example, oxygen dissolved in a liquid will escape into a nitrogen atmosphere in the same way as into a void, even when the nitrogen is under very high pressure.

When a liquid comes into contact with a gas mixture of a certain composition, the amount of gas entering or leaving the liquid depends not only on the ratio of gas pressures in the liquid and in the gas mixture, but also on their volumes. If a large volume of liquid comes into contact with a large volume of a gas mixture, the pressure of which differs sharply from the pressure of the gases in the liquid, then large quantities of gas may leave or enter it. On the contrary, if a sufficiently large volume of liquid comes into contact with a gas bubble of small volume, then a very small amount of gas will leave or enter the liquid and the gas composition of the liquid will remain virtually unchanged.

For gases dissolved in a liquid, the term “ voltage", corresponding to the term "partial pressure" for free gases. Voltage is expressed in the same units as pressure, i.e. in atmospheres or millimeters of mercury or water column. If the gas voltage is 1.00 mmHg. Art., this means that the gas dissolved in the liquid is in equilibrium with the free gas under a pressure of 100 mm.

If the tension of the dissolved gas is not equal to the partial pressure of the free gas, then the equilibrium is disturbed. It is restored when these two quantities become equal to each other again. For example, if the oxygen tension in the liquid of a closed vessel is 100 mm, and the oxygen pressure in the air of this vessel is 150 mm, then oxygen will enter the liquid.

In this case, the oxygen tension in the liquid will increase, and its pressure outside the liquid will decrease until a new dynamic equilibrium is established and both of these values ​​are equal, receiving some new value between 150 and 100 mm. How pressure and voltage change in a given flow depends on the relative volumes of gas and liquid.