Even in the last century, various studies were carried out on the effect of CO 2 on the human body. In the 60s, the scientist O.V. Eliseeva in her dissertation conducted a detailed study of how carbon dioxide in concentrations of 0.1% (1000 ppm) to 0.5% (5000 ppm) affects the human body and came to the conclusion that short-term inhalation of carbon dioxide by healthy people in these concentrations causes distinct changes in the function of external respiration, blood circulation and a significant deterioration in the electrical activity of the brain. According to her recommendations, the content of CO 2 in the air of residential and public buildings should not exceed 0.1% (1000 ppm), and the average content of CO 2 should be about 0.05% (500 ppm).

Experts know that there is a direct relationship between the concentration of CO 2 and the feeling of stuffiness. This feeling occurs in a healthy person already at the level of 0.08% (i.e. 800 ppm). Although in modern offices it is very common to have 2000 ppm or more. And a person may not feel the dangerous effects of CO 2 . When it comes to a sick person, the threshold of his sensitivity increases even more.

The dependence of physiological manifestations on the CO2 content in the air is given in the table:

CO 2 level, ppm	Physiological manifestations in humans
Atmospheric air 380-400	Ideal for health and wellness.
400-600	Normal amount. Recommended for children's rooms, bedrooms, offices, schools and kindergartens.
600-1000	There are complaints about air quality. People with asthma may have more frequent attacks.
Above 1000	General discomfort, weakness, headache, concentration of attention falls by a third, the number of errors in work is growing. It can lead to negative changes in the blood, and problems with the respiratory and circulatory systems may also appear.
Above 2000	The number of errors in the work is greatly increasing, 70% of employees cannot concentrate on work.

The main changes during inhalation of elevated concentrations of carbon dioxide (hypercapnia) occur in the central nervous system, and they are of a phase nature: first, an increase, and then a decrease in excitability nerve formations. Deterioration of conditioned reflex activity is observed at concentrations close to 2% - the excitability of the respiratory center of the brain decreases, the ventilatory function of the lungs decreases, homeostasis (balance of the internal environment) of the body is disturbed either by damaging cells or by irritating receptors with an inadequate level of a certain substance. And when the carbon dioxide content is up to 5%, there is a significant decrease in the amplitude of the evoked potentials of the brain, desynchronization of the rhythms of the spontaneous electroencephalogram with further inhibition of the electrical activity of the brain.

What exactly happens when the concentration of CO 2 in the air that enters the body increases? The partial pressure of CO 2 in the alveoli increases, its solubility in the blood increases, and a weak carbonic acid(CO 2 + H 2 O \u003d H 2 CO 3), which, in turn, decomposes into H + and HCCO3-. The blood becomes acidic, which is scientifically called gas acidosis. The higher the concentration of CO 2 in the air we breathe, the lower the pH of the blood and the more acidic it is.

Employee of the Medical Research Laboratory of the Naval submarine fleet USA Carl Schafer investigated how different concentrations of carbon dioxide affect guinea pigs. Rodents were kept at 0.5% CO 2 for eight weeks (oxygen was normal - 21%), after which they observed significant kidney calcification. It was noted even after prolonged exposure of guinea pigs to lower concentrations - 0.3% CO 2 (3000 ppm). But that is not all. Schafer and colleagues found bone demineralization in gilts after eight weeks of exposure to 1% CO 2 , as well as structural changes in the lungs. The researchers regarded these diseases as an adaptation of the body to chronic exposure. advanced level CO2.

The hallmark of long-term hypercapnia (elevated CO2) is the long-term negative effects. Despite the normalization of atmospheric respiration, in the human body long time there are changes in the biochemical composition of the blood, a decrease in the immunological status, resistance to physical exertion and other external influences.

Conclusion to avoid negative consequences, the content of carbon dioxide in the inhaled air must be monitored. For this purpose, a modern and reliable device is perfect -

The normal functioning of all vital systems depends on the amount of carbon dioxide in the human bloodstream. Carbon dioxide increases the body's resistance to bacterial and viral infections, participates in the exchange of biologically active substances. During physical and intellectual stress, carbon dioxide helps to maintain the balance of the body. But a significant increase in this chemical compound in the surrounding atmosphere worsens a person's well-being. The harm and benefits of carbon dioxide for the existence of life on Earth have not yet been fully studied.

Characteristic features of carbon dioxide

Carbon dioxide, carbonic anhydride, carbon dioxide is a gaseous chemical compound that is colorless and odorless. The substance is 1.5 times heavier than air, and its concentration in the Earth's atmosphere is approximately 0.04%. A distinctive feature of carbon dioxide is the absence of a liquid form with increasing pressure - the compound immediately turns into solid state known as "dry ice". But when certain artificial conditions are created, carbon dioxide takes the form of a liquid, which is widely used for its transportation and long-term storage.

Interesting fact

Carbon dioxide does not become a barrier to ultraviolet rays that enter the atmosphere from the Sun. But the infrared radiation of the Earth is absorbed by carbon anhydride. This is what causes global warming since the formation of a huge number of industrial production.

During the day, the human body absorbs and metabolizes about 1 kg of carbon dioxide. She takes an active part in the metabolism that occurs in soft, bone, articular tissues, and then enters the venous bed. With the flow of blood, carbon dioxide enters the lungs and leaves the body with each exhalation.

The chemical is found in the human body primarily in the venous system. The capillary network of lung structures and arterial blood contain a small concentration of carbon dioxide. In medicine, the term "partial pressure" is used, which characterizes the concentration ratio of a compound in relation to the entire volume of blood.

Therapeutic properties of carbon dioxide

The penetration of carbon dioxide into the body causes a respiratory reflex in humans. Increasing the pressure of a chemical compound provokes thin nerve endings send impulses to the receptors of the brain and (and) spinal cord. This is how the process of inhalation and exhalation occurs. If the level of carbon dioxide in the blood begins to rise, then the lungs accelerate its removal from the body.

Interesting fact

Scientists have proven that the significant life expectancy of people living in the highlands is directly related to the high content of carbon dioxide in the air. It improves immunity, normalizes metabolic processes, strengthens the cardiovascular system.

In the human body, carbon dioxide is one of the most important regulators, acting as the main product along with molecular oxygen. The role of carbon dioxide in the process of human life is difficult to overestimate. The main functional features of the substance include the following:

• has the ability to cause persistent expansion of large vessels and capillaries;
• it is able to have a sedative effect on the central nervous system, provoking an anesthetic effect;
• takes part in the production of essential amino acids;
• excites the respiratory center with an increase in concentration in the bloodstream.

If there is an acute shortage of carbon dioxide in the body, then all systems are mobilized and increase their functional activity. All processes in the body are aimed at replenishing carbon dioxide reserves in the tissues and bloodstream:

• the vessels narrow, bronchospasm develops in the smooth muscles of the upper and lower respiratory tract, as well as blood vessels;
• bronchi, bronchioles, structural sections of the lungs secrete an increased amount of mucus;
• the permeability of large and small blood vessels, capillaries decreases;
• cholesterol begins to be deposited on cell membranes, which causes their thickening and tissue sclerosis.

The combination of all these pathological factors, combined with a low supply of molecular oxygen, leads to tissue hypoxia and a decrease in the rate of blood flow in the veins. Oxygen starvation is especially acute in brain cells, they begin to break down. The regulation of all vital systems is disrupted: the brain and lungs swell, the heart rate decreases. In the absence of medical intervention, a person may die.

Where is carbon dioxide used?

Carbon dioxide is found not only in the human body and in the surrounding atmosphere. Many industries are actively using Chemical substance at various stages of technological processes. It is used as:

• stabilizer;
• catalyst;
• primary or secondary raw materials.

Interesting fact

Oxygen dioxide contributes to the transformation into a delicious tart house wine. Fermentation of the sugar contained in the berries releases carbon dioxide. It gives the drink sparkling, allows you to feel the bursting bubbles in your mouth.
On food packaging, carbon dioxide is hidden under the code E290. As a rule, it is used as a preservative for long-term storage. When baking delicious cupcakes or pies, many housewives add baking powder to the dough. During the cooking process, air bubbles are formed, making the muffin fluffy, soft. This is carbon dioxide chemical reaction between sodium bicarbonate and food acid. Aquarium fish lovers use the colorless gas as an aquatic plant growth activator, and manufacturers of automatic carbon dioxide systems put it in fire extinguishers.

Harm of carbonic anhydride

Children and adults are very fond of a variety of fizzy drinks for the air bubbles they contain. These pockets of air are pure carbon dioxide released when the bottle cap is unscrewed. Used in this capacity, it does not bring any benefit to the human body. Getting into the gastrointestinal tract, carbonic anhydride irritates the mucous membranes, provokes damage to epithelial cells.

For a person with diseases of the stomach, it is highly undesirable to use it, since under their influence the inflammatory process and ulceration of the inner wall of the organs of the digestive system intensifies.

Gastroenterologists forbid drinking lemonade and mineral water patients with the following pathologies:

• acute, chronic, catarrhal gastritis;
• stomach and duodenal ulcer;
• duodenitis;
• decreased intestinal motility;
• benign and malignant neoplasms of the gastrointestinal tract.

It should be noted that according to WHO statistics, more than half of the inhabitants of the planet Earth suffer from one form or another of gastritis. The main symptoms of stomach disease are sour belching, heartburn, bloating and pain in the epigastric region.

If a person is unable to refuse the use of drinks with carbon dioxide, then he should opt for slightly carbonated mineral water.

Experts advise to exclude lemonade from the daily diet. After the statistical studies In people who drank sweet water with carbon dioxide for a long time, the following diseases were identified:

• caries;
• endocrine disorders;
• increased fragility of bone tissue;
• fatty degeneration of the liver;
• the formation of stones in the bladder and kidneys;
• disorders of carbohydrate metabolism.

Employees of office premises that are not equipped with air conditioners often experience excruciating headaches, nausea, and weakness. This condition in humans occurs when there is an excessive accumulation of carbon dioxide in the room. Constant presence in such an environment leads to acidosis (increased acidity of the blood), provokes a decrease in the functional activity of all vital systems.

Benefits of carbon dioxide

The healing effect of carbon dioxide on the human body is widely used in medicine in the treatment of various diseases. So, in recent years, dry carbonic baths have been very popular. The procedure consists in the effect of carbon dioxide on the human body in the absence of extraneous factors: water pressure and ambient temperature.

Beauty salons and medical institutions offer clients unusual medical manipulations:

• pneumopuncture;
• carboxytherapy.

Under complex terms hiding gas injections or carbon dioxide injections. Such procedures can be attributed both to varieties of mesotherapy and to methods of rehabilitation after serious illnesses.

Before carrying out these procedures, you should visit your doctor for a consultation and a thorough diagnosis. Like all methods of therapy, carbon dioxide injections have contraindications for use.

Useful properties of carbon dioxide are used in the treatment of cardiovascular diseases, arterial hypertension. And dry baths reduce the content of free radicals in the body, have a rejuvenating effect. Carbon dioxide increases a person's resistance to viral and bacterial infections, strengthens the immune system, and increases vitality.

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The study of the effect of the toxic effect of CO 2 on the human body is of significant practical interest for biology and medicine.

The source of CO 2 in the gaseous environment of a pressurized cabin is, first of all, the person himself, since CO 2 is one of the main end products of metabolism formed in the process of metabolism in humans and animals. At rest, a person emits about 400 liters of CO 2 per day, during physical work, the formation of CO 2 and, accordingly, its release from the body increase significantly. In addition, it must be borne in mind that CO 2 is continuously formed in the process of decay and fermentation. Carbon dioxide is colorless, has a slight odor and a sour taste. Despite these qualities, when CO 2 is accumulated in IHA up to a few percent, its presence is imperceptible to humans, since the properties mentioned above (smell and taste) can apparently be detected only at very high CO 2 concentrations.

Breslav's studies, in which the subjects made a "free choice" of the gas medium, showed that people begin to avoid IHA only in those cases when the PCO 2 in it exceeds 23 mm Hg. Art. At the same time, the reaction of detecting CO 2 is not associated with smell and taste, but with the manifestation of its effect on the body, primarily with an increase in pulmonary ventilation and a decrease in physical performance.

IN earth's atmosphere contains a small amount of CO 2 (0.03%), due to its participation in the circulation of substances. A tenfold increase in CO 2 in the inhaled air (up to 0.3%) does not yet have a noticeable effect on human life and work capacity. In such a gaseous environment, a person can stay for a very long time, maintaining a normal state of health and a high level of efficiency. This is probably due to the fact that in the course of life, the formation of CO 2 in tissues is subject to significant fluctuations, exceeding tenfold changes in the content of this substance in the inhaled air. A significant increase in P CO 2 in IHA causes regular changes in the physiological state. These changes are primarily due to functional shifts that occur in the central nervous system, respiration, blood circulation, as well as shifts in acid-base balance and mineral metabolism disorders. The nature of functional shifts in hypercapnia is determined by the value of P CO 2 in the inhaled gas mixture and the time of exposure of this factor to the body.

Even Claude Bernard in the last century showed that the main reason for the development of a severe pathological condition in animals during their long stay in hermetically closed, unventilated rooms is associated with an increase in the CO 2 content in the inhaled air. Animal studies have studied the mechanism of physiological and pathological action of CO 2 .

The physiological mechanism of the influence of hypercapnia can be judged in general terms on the basis of the scheme shown in Fig. 19.

It should be borne in mind that in cases of long-term stay in the IHA, in which R CO 2 is increased to 60-70 mm Hg. Art. and more, the nature of physiological reactions and, above all, reactions of the central nervous system changes significantly. In the latter case, instead of a stimulating effect, as shown in Fig. 19, hypercapnia has a depressing effect and already leads to the development of a narcotic state. It quickly occurs in cases where P CO 2 increases to 100 mm Hg. Art. and higher.

Strengthening of pulmonary ventilation with an increase in P CO 2 in the IHA up to 10-15 mm Hg. Art. and higher is determined by at least two mechanisms: reflex stimulation of the respiratory center from the chemoreceptors of the vascular zones, and primarily sino-corotid, and stimulation of the respiratory center from the central chemoreceptors. The growth of pulmonary ventilation during hypercapnia is the main adaptive reaction of the body, aimed at maintaining Pa CO 2 at normal level. The effectiveness of this reaction decreases with increasing P CO 2 in IHA, because despite the increasing increase in pulmonary ventilation, Pa CO 2 also steadily increases.

The growth of Pa CO 2 has an antagonistic effect on the central and peripheral mechanisms that regulate vascular tone. The stimulating effect of CO 2 on the vasomotor center, the sympathetic nervous system determines the vasoconstrictive effect and leads to an increase in peripheral resistance, an increase in heart rate and an increase in cardiac output. At the same time, CO 2 also has a direct effect on the muscular wall of blood vessels, contributing to their expansion.

Rice. 19. Mechanisms of the physiological and pathophysiological effects of CO 2 on the body of animals and humans (according to Malkin)

The interaction of these antagonistic influences ultimately determines the reactions of the cardiovascular system during hypercapnia. From the foregoing, it can be concluded that in the case of a sharp decrease in the central vasoconstrictor effect, hypercapnia can lead to the development of collaptoid reactions, which were noted in animal experiments under conditions of a significant increase in the CO2 content in IHA.

With a large increase in P CO 2 in tissues, which inevitably occurs under conditions of a significant increase in P CO 2 in IHA, the development of a narcotic state is noted, which is accompanied by a clearly pronounced decrease in the level of metabolism. This reaction can be assessed in the same way as adaptive, since it leads to a sharp decrease in the formation of CO 2 in tissues during the period when transport systems, including blood buffer systems, are no longer able to maintain Pa CO 2 - the most important constant of the internal environment. at a level close to normal.

It is important that the threshold of reactions of various functional systems during the development of acute hypercapnia is not the same.

Thus, the development of hyperventilation manifests itself already with an increase in P CO 2 in the IHA to 10-15 mm Hg. Art., and at 23 mm Hg. Art. this reaction becomes already very pronounced - ventilation increases almost 2 times. The development of tachycardia and an increase in blood pressure appear when P CO 2 increases in the IHA to 35-40 mm Hg. Art. The narcotic effect was noted at even higher values ​​of P CO 2 in IHA, about 100-150 mm Hg. Art., while the stimulating effect of CO 2 on the neurons of the cortex hemispheres of the brain was noted at R CO 2 of the order of 10-25 mm Hg. Art.

Let us now briefly consider the effects of various PCO 2 values ​​in IHA on the body of a healthy person.

Of great importance for judging a person's resistance to hypercapnia and for normalizing CO 2 are studies in which subjects, practically healthy people, were in IHA conditions with excessive values ​​of P CO 2 . In these studies, the nature and dynamics of the reactions of the central nervous system, respiration and blood circulation, as well as changes in working capacity at various values ​​of P CO 2 in IHA were established.

With a relatively short stay of a person in IGA conditions with P CO 2 up to 15 mm Hg. Art., despite the development of mild respiratory acidosis, no significant changes in the physiological state were found. People who were in such an environment for several days retained normal intellectual performance and did not show complaints indicating a deterioration in well-being; only at R CO 2 equal to 15 mm Hg. Art., some subjects noted a decrease in physical performance, especially when performing hard work.

With an increase in R CO 2 in the IHA up to 20-30 mm Hg. Art. the subjects had a pronounced respiratory acidosis and an increase in pulmonary ventilation. After a relatively brief increase in execution speed psychological tests there was a decrease in the level of intellectual performance. The ability to perform heavy physical work was also markedly reduced. Sleep disturbance was noted. Many of the respondents complained about headache, dizziness, shortness of breath and a feeling of lack of air when performing physical work.

Rice. 20. Classification of various effects of the toxic action of CO 2 depending on the value of P CO 2 in IHA (compiled by Roth and Billings according to Schaeffer, King, Nevison)

I - indifferent zone;

L - zone of minor physiological changes;

III - zone of pronounced discomfort;

IV - zone of deep functional disorders, loss

consciousness A - indifferent zone;

B - zone of initial functional disorders;

B - aeon of deep disturbances

With an increase in P CO 2 in the IHA up to 35-40 mm Hg. Art. in the subjects, pulmonary ventilation increased by 3 times or more. There were functional shifts in the circulatory system: the heart rate increased, blood pressure increased. After a short stay in such an IHA, the subjects complained of headache, dizziness, visual disturbances, loss of spatial orientation. Performing even light physical activity was associated with significant difficulties and led to the development of severe shortness of breath. The performance of psychological tests was also difficult, intellectual performance was noticeably reduced. With an increase in R CO 2 in the IHA more than 45-50 mm Hg. Art. acute hypercapnic disorders occurred very quickly - within 10-15 minutes.

The generalization of data published in the literature on human resistance to the toxic effects of CO 2 , as well as the establishment of the maximum allowable time for a person to stay in IHA with a high content of CO 2, encounters certain difficulties. They are primarily related to the fact that a person's resistance to hypercapnia largely depends on the physiological state and, first of all, on the amount of physical work performed. Most famous works studies were conducted with subjects who were in conditions of relative rest and only periodically performed various psychological tests.

Based on the generalization of the results obtained in these works, it was proposed to conditionally distinguish four different zones of the toxic effect of hypercapnia, depending on the value of P CO 2 in IHA (Fig. 20).

Essential for the formation of physiological reactions and human resistance to hypercapnia is the rate of growth of the value of P CO 2 in the inhaled gas mixture. When a person is placed in IHA with a high PCO 2 , as well as when he switches to breathing with a gas mixture enriched with CO 2 , a rapid increase in RA CO 2 is accompanied by a more acute course of hypercapnic disorders than with a slow increase in P CO 2 in IHA. Fortunately, the latter is more characteristic of the toxic effect of CO 2 under space flight conditions, since the ever-increasing volume of spacecraft cabins determines a relatively slow increase in PCO 2 in the IHA in cases of failure of the air regeneration system. A more acute course of hypercapnia can occur when the spacesuit regeneration system fails. In acute hypercapnia, the difficulty of accurately distinguishing between zones that determine qualitatively different manifestations of the toxic effect of CO 2, depending on the value of Р CO 2, is associated with the presence of the “primary adaptation” phase, the duration of which is the longer, the higher the CO 2 concentration. We are talking about the fact that after a person quickly enters the IHA containing a high concentration of CO 2, there are pronounced changes in the body, which, as a rule, are accompanied by the appearance of complaints of headache, dizziness, loss of spatial orientation, visual disturbances, nausea, lack of air , chest pain. All this led to the fact that often the study was terminated after 5-10 minutes. after the subject's transition to hypercapnic IHA.

Published studies show that with an increase in P CO 2 in IHA up to 76 mm Hg. Art. such an unstable state gradually passes and there appears, as it were, a partial adaptation to the changed gaseous medium. The subjects show some normalization of intellectual performance, and at the same time, complaints of headache, dizziness, visual disturbances, etc. become more moderate. The duration of the unstable state is determined by the time during which RA CO 2 increases and a continuous increase in pulmonary ventilation is noted. Shortly after stabilization at a new level of RA CO 2 and lung ventilation, partial adaptation develops, accompanied by an improvement in the well-being and general condition of the subjects. Such dynamics of the development of acute hypercapnia at high values ​​of PCO 2 in IHA was the reason for significant discrepancies in the assessment by different researchers of the possible time spent by a person in these conditions.

On fig. 20 when evaluating the influence of different values ​​of P CO 2 "primary adaptation" although taken into account in time, however, it is not indicated that the physiological state of a person is not the same in different periods of stay in the IHA with a high content of CO 2 . Once again, it is worth noting that the results presented in Fig. 20 obtained in studies during which the subjects were at rest. In this regard, the data obtained without an appropriate correlation cannot be used to predict changes in the physiological state of cosmonauts in cases of CO 2 accumulation in the IHA, since in flight it may be necessary to perform physical work of varying intensity.

It has been established that a person's resistance to the toxic effect of CO 2 decreases with an increase in physical activity that he performs. In this regard, studies in which the toxic effect of CO 2 would be studied in practically healthy people performing physical work of varying severity. Unfortunately, such information is scarce in the literature, and therefore this issue needs further study. Nevertheless, on the basis of the available data, we considered it appropriate, with a certain approximation, to indicate the possibility of staying and performing various physical loads in the IHA, depending on the value of P CO 2 in it.

As can be seen from the data given in table. 6, with an increase in R CO 2 to 15 mm Hg. Art. long-term performance of hard physical work is difficult; with increases in R CO 2 up to 25 mm Hg. Art. the ability to perform work of moderate severity is already limited and the performance of heavy work is noticeably difficult. With an increase in R CO 2 to 35-40 mm Hg. Art. limited ability to perform even light work. With an increase in R CO 2 to 60 mm Hg. Art. and more, despite the fact that a person in a state of rest can still be in such an IHA for some time, but he is already practically unable to do any work. For removal negative influence acute hypercapnia, the best remedy is to transfer the victims to a "normal" atmosphere.

The results of studies by many authors show that the rapid switching of people who have been in IHA for a long time with elevated P CO 2 to breathing pure oxygen or air often causes a deterioration in their well-being and general condition. This phenomenon, expressed in a sharp form, was first discovered in experiments on animals and described by P. M. Albitsky, who gave it the name of the reverse action of CO 2 . In connection with the above, in cases of development of hypercapnic syndrome in people, one should gradually withdraw them from IHA enriched with CO 2, relatively slowly reducing P CO 2 in it. Attempts to stop the hypercapnic syndrome by introducing alkalis - Tris buffer, soda, etc. - did not give stable positive results, despite the partial normalization of blood pH.

Of certain practical importance is the study of the physiological state and working capacity of a person in cases where, as a result of a failure of the regeneration unit in the IHA, P O 2 will simultaneously decrease and P CO 2 will increase.

With a significant rate of increase in CO 2 and the corresponding rate of decrease in O 2, which occurs when breathing in a closed, small volume, as studies by Holden and Smith showed, a sharp deterioration in the physiological state and well-being of the subjects is noted with an increase in CO 2 in the inhaled gas mixtures to 5-6% (P CO 2 -38-45 mm Hg), despite the fact that the decrease in the content of O 2 in this period of time was still relatively small. With a slower development of hypercapnia and hypoxia, as many authors point out, noticeable performance disorders and a deterioration in the physiological state are observed with an increase in P CO 2 to 25-30 mm Hg. Art. and a corresponding decrease in R O 2 to 110-120 mm Hg. Art. According to Karlin et al., 3-day exposure to IHA containing 3% CO 2 (22.8 mm Hg) and 17% O 2 significantly reduced the performance of the subjects. These data are in some contradiction with the results of studies that noted relatively small changes in performance even with a more significant (up to 12%) decrease in O 2 in IHA and an increase in CO 2 in it up to 3%.

With the simultaneous development of hypercapnia and hypoxia, the main symptom of the toxic effect is shortness of breath. The value of lung ventilation in this case is more significant than with equal hypercapnia. According to many researchers, such a significant increase in pulmonary ventilation is determined by the fact that hypoxia increases the sensitivity of the respiratory center to CO 2, resulting in the combined effect of excess CO 2 and lack of O 2

in IGA does not lead to an additive effect of these factors, but to their potentiation. This can be judged because the value of pulmonary ventilation is greater than the value of ventilation, which should have been with a simple addition of the effect of a decrease in RA O 2 and an increase in RA CO 2.

Based on these data and the nature of the observed violations of the physiological state, it can be concluded that the leading role in the initial period of the development of pathological conditions in situations where there is a complete failure of the regeneration system belongs to hypercapnia.

CHRONIC EFFECTS OF HYPERCAPNIA

The study of long-term effects on the human body and animals elevated; The values ​​of P CO 2 in IHA made it possible to establish that the appearance of clinical symptoms of the storage toxic effect of CO 2 is preceded by regular changes in acid-base balance - the development of respiratory acidosis, leading to metabolic disorders. In this case, shifts occur in mineral metabolism, which, apparently, are of an adaptive nature, since they contribute to maintaining the acid-base balance. These changes can be judged by a periodic increase in the content of calcium in the blood and by changes in the content of calcium and phosphorus in the bone tissue. Due to the fact that calcium enters into compounds with CO 2, with an increase in Pa CO 2, the amount of CO 2 associated with calcium in the bones increases. As a result of shifts in mineral metabolism, a situation arises that promotes the formation of calcium salts in the excretory system, which may result in the development of kidney stone disease. The validity of this conclusion is indicated by the results of a study on rodents, in which, after a long stay in the IHA with R CO 2 equal to 21 mm Hg. Art. and above, kidney stones were found.

In studies involving people, it was also found that in cases of prolonged stay in the IHA with P CO 2 exceeding 7.5-10 mm Hg. Art., despite the apparent preservation of the normal physiological state and performance, the subjects showed changes in metabolism due to the development of moderate gaseous acidosis.

So, during the operation "Hideout" the subjects were within 42 days in a submarine in the conditions of the IGA, containing 1.5% CO 2 (P CO 2 - 11.4 mm Hg. Art.). Basic physiological parameters, such as weight and body temperature, blood pressure and pulse rate, remained unchanged. However, in the study of respiration, acid-base balance and calcium-phosphorus metabolism, shifts were found that had an adaptive character. Based on changes in the pH of urine and blood, it was found that from about the 24th day of stay in the IHA containing 1.5% CO 2, the subjects developed uncompensated gaseous acidosis. According to the data of S. G. Zharov et al., when young healthy men were kept in IHA containing 1% CO 2 for a month, no changes in blood pH were found in the subjects, despite a slight increase in RA CO 2 and an increase of 8-12% in pulmonary ventilation, indicating a slight compensable gas acidosis.

Long-term stay (30 days) of the subjects in the IHA with a CO 2 content increased to 2% led to a decrease in blood pH, an increase in RA CO 2 and an increase in pulmonary ventilation by 20-25%. At rest, the subjects felt good, however, when performing intense physical activity, some of them complained of headache and rapid fatigue.

While in the IHA with 3% CO 2 (P CO 2 - 22.8 mm Hg. Art.), Most of the subjects noted a deterioration in health. At the same time, changes in blood pH indicate rapid development uncompensated gaseous acidosis. Staying in such an environment, although it is possible for many days, is always associated with the development of discomfort and a progressive decrease in performance.

As a result of these studies, it was concluded that a long-term (multi-month) stay of a person in the IHA with R CO 2 exceeding 7.5 mm Hg. Art., is undesirable, as it can lead to the manifestation of chronic toxic effects of CO 2 . Some researchers indicate that when a person stays in the IHA for 3-4 months, the value of P CO 2 should not exceed 3-6 mm Hg. st..

Thus, when evaluating the effect of the chronic effect of hypercapnia as a whole, one can agree with the opinion of K. Schaefer on the expediency of distinguishing three main levels of an increase in P CO 2 in IHA, which determine the different tolerance of a person to hypercapnia. The first level corresponds to an increase in R CO 2 in the IHA up to 4-6 mm Hg. Art.; it is characterized by the absence of any significant effect on the body. The second level corresponds to an increase in R CO 2 in IHA up to 11 mm Hg. Art. At the same time, the basic physiological functions and working capacity do not undergo significant changes, however, there is a slow development of shifts in respiration, regulation

acid-base balance and electrolyte metabolism, resulting in pathological changes.

The third level is an increase in R CO 2 to 22 mm Hg. Art. and above - leads to a decrease in performance, pronounced shifts physiological functions and development through various time periods of pathological conditions.

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Soda, volcano, Venus, refrigerator - what do they have in common? Carbon dioxide. We have collected for you the most interesting information about one of the most important chemical compounds on the ground.

What is carbon dioxide

Carbon dioxide is known mainly in its gaseous state, i. as carbon dioxide with simple chemical formula CO2. In this form it exists in normal conditions– at atmospheric pressure and “ordinary” temperatures. But at increased pressure, over 5,850 kPa (such, for example, the pressure at a sea depth of about 600 m), this gas turns into a liquid. And with strong cooling (minus 78.5 ° C), it crystallizes and becomes the so-called dry ice, which is widely used in trade for storing frozen foods in refrigerators.

Liquid carbon dioxide and dry ice are produced and used in human activities, but these forms are unstable and break down easily.

But gaseous carbon dioxide is ubiquitous: it is released during the respiration of animals and plants and is an important part of the chemical composition of the atmosphere and ocean.

Properties of carbon dioxide

Carbon dioxide CO2 is colorless and odorless. IN normal conditions it has no taste either. However, when inhaling high concentrations of carbon dioxide, a sour taste can be felt in the mouth, caused by the fact that carbon dioxide dissolves on mucous membranes and in saliva, forming a weak solution of carbonic acid.

By the way, it is the ability of carbon dioxide to dissolve in water that is used to make sparkling waters. Bubbles of lemonade - the same carbon dioxide. The first apparatus for saturating water with CO2 was invented as early as 1770, and already in 1783, the enterprising Swiss Jacob Schwepp began the industrial production of soda (the Schweppes trademark still exists).

Carbon dioxide is 1.5 times heavier than air, so it tends to “settle” in its lower layers if the room is poorly ventilated. The “dog cave” effect is known, where CO2 is released directly from the ground and accumulates at a height of about half a meter. An adult, getting into such a cave, at the height of his height does not feel an excess of carbon dioxide, but dogs find themselves right in a thick layer of carbon dioxide and are poisoned.

CO2 does not support combustion, so it is used in fire extinguishers and fire suppression systems. The trick with extinguishing a burning candle with the contents of an allegedly empty glass (but in fact with carbon dioxide) is based precisely on this property of carbon dioxide.

Carbon dioxide in nature: natural sources

Carbon dioxide is produced in nature from various sources:

• Breathing of animals and plants.
  Every schoolchild knows that plants absorb carbon dioxide CO2 from the air and use it in photosynthesis. Some housewives try with abundance indoor plants atone for shortcomings. However, plants not only absorb but also release carbon dioxide in the absence of light as part of the respiration process. Therefore, a jungle in a poorly ventilated bedroom is not a good idea: at night, CO2 levels will rise even more.
• Volcanic activity.
  Carbon dioxide is part of volcanic gases. In areas with high volcanic activity, CO2 can be released directly from the ground - from cracks and faults called mofet. The concentration of carbon dioxide in mofet valleys is so high that many small animals die when they get there.
• decomposition of organic matter.
  Carbon dioxide is formed during combustion and decay of organic matter. Volumetric natural emissions of carbon dioxide accompany forest fires.

Carbon dioxide is "stored" in nature in the form of carbon compounds in minerals: coal, oil, peat, limestone. Huge reserves of CO2 are found in dissolved form in the world's oceans.

The release of carbon dioxide from an open reservoir can lead to a limnological catastrophe, as happened, for example, in 1984 and 1986. in lakes Manun and Nyos in Cameroon. Both lakes were formed on the site of volcanic craters - now they are extinct, but in the depths, volcanic magma still emits carbon dioxide, which rises to the waters of the lakes and dissolves in them. As a result of a number of climatic and geological processes, the concentration of carbon dioxide in the waters exceeded the critical value. A huge amount of carbon dioxide was released into the atmosphere, which, like an avalanche, descended along the mountain slopes. About 1,800 people became victims of limnological disasters on the Cameroonian lakes.

Artificial sources of carbon dioxide

The main anthropogenic sources of carbon dioxide are:

• industrial emissions associated with combustion processes;
• automobile transport.

Despite the fact that the share of environmentally friendly transport in the world is growing, the vast majority of the world's population will not soon be able (or willing) to switch to new cars.

Active deforestation for industrial purposes also leads to an increase in the concentration of carbon dioxide CO2 in the air.

CO2 is one of the end products of metabolism (the breakdown of glucose and fats). It is secreted in the tissues and carried by hemoglobin to the lungs, through which it is exhaled. In the air exhaled by a person, there is about 4.5% carbon dioxide (45,000 ppm) - 60-110 times more than in the inhaled air.

Carbon dioxide plays an important role in the regulation of blood supply and respiration. An increase in the level of CO2 in the blood causes the capillaries to expand, allowing more blood to pass through, which delivers oxygen to the tissues and removes carbon dioxide.

The respiratory system is also stimulated by an increase in carbon dioxide, and not by a lack of oxygen, as it might seem. In fact, the lack of oxygen is not felt by the body for a long time, and it is quite possible that in rarefied air a person will lose consciousness before he feels a lack of air. The stimulating property of CO2 is used in artificial respiration devices: there, carbon dioxide is mixed with oxygen to "start" the respiratory system.

Carbon dioxide and us: why is CO2 dangerous?

Carbon dioxide is as essential to the human body as oxygen. But just like with oxygen, an excess of carbon dioxide harms our well-being.

A high concentration of CO2 in the air leads to intoxication of the body and causes a state of hypercapnia. In hypercapnia, a person experiences difficulty breathing, nausea, headache, and may even pass out. If the carbon dioxide content does not decrease, then the turn comes - oxygen starvation. The fact is that both carbon dioxide and oxygen move around the body on the same "transport" - hemoglobin. Normally, they "travel" together, attaching to different places on the hemoglobin molecule. However, an increased concentration of carbon dioxide in the blood reduces the ability of oxygen to bind to hemoglobin. The amount of oxygen in the blood decreases and hypoxia occurs.

Such unhealthy consequences for the body occur when inhaling air with a CO2 content of more than 5,000 ppm (this can be the air in mines, for example). In fairness, in ordinary life we ​​practically do not encounter such air. However, even a much lower concentration of carbon dioxide is not good for health.

According to the findings of some, already 1,000 ppm CO2 causes fatigue and headache in half of the subjects. Many people begin to feel closeness and discomfort even earlier. With a further increase in the concentration of carbon dioxide to 1,500 - 2,500 ppm, the brain is "lazy" to take the initiative, process information and make decisions.

And if the level of 5,000 ppm is almost impossible in Everyday life, then 1,000 and even 2,500 ppm can easily be part of reality modern man. Ours showed that in rarely ventilated school classes CO2 levels stay above 1,500 ppm most of the time, and sometimes jump above 2,000 ppm. There is every reason to believe that the situation is similar in many offices and even apartments.

Physiologists consider 800 ppm as a safe level of carbon dioxide for human well-being.

Another study found a connection between CO2 levels and oxidative stress: the higher the level of carbon dioxide, the more we suffer from, which destroys the cells of our body.

Carbon dioxide in the earth's atmosphere

In the atmosphere of our planet, there is only about 0.04% CO2 (this is approximately 400 ppm), and more recently it was even less: carbon dioxide crossed the mark of 400 ppm only in the fall of 2016. Scientists attribute the rise in CO2 levels in the atmosphere to industrialization: in mid-eighteenth century, on the eve of the industrial revolution, it was only about 270 ppm.

Scientists have long suspected that carbon dioxide is directly related to global warming, but as it turns out, carbon dioxide can have a direct bearing on our health. Humans are the main source of indoor carbon dioxide, as we breathe out 18 to 25 liters of this gas per hour. Increased content carbon dioxide levels can be observed in all areas where people are: in school classrooms and institute auditoriums, in meeting rooms and office spaces, in bedrooms and children's rooms.

The fact that we do not have enough oxygen in a stuffy room is a myth. Calculations show that, contrary to the existing stereotype, headache, weakness, and other symptoms occur in a person in a room not from a lack of oxygen, but from an excess of carbon dioxide.

Until recently, in European countries and the United States, the level of carbon dioxide in a room was measured only in order to check the quality of ventilation, and it was believed that CO2 was dangerous for humans only in high concentrations. Studies on the effect of carbon dioxide on the human body at a concentration of approximately 0.1% appeared quite recently.

Few people know that clean air outside the city contains about 0.04% carbon dioxide, and the closer the CO2 content in the room is to this figure, the better a person feels.

According to the latest research conducted in the UK by a large accounting firm KPMG, high levels of CO2 in the air of an office space can cause sickness among employees and reduce their concentration by a third. Elevated levels of carbon dioxide can cause headaches, inflammation of the eyes and nasopharynx, and cause fatigue among staff. As a result of all this, companies are losing a lot of money, and carbon dioxide is to blame. Julie Bennett, who led the research, says that high levels of carbon dioxide in office spaces are very common.

As a result of recent studies conducted by Indian scientists among the inhabitants of the city of Kolkata, it was found that even in low concentrations, carbon dioxide is a potentially toxic gas. Scientists have concluded that carbon dioxide is close in toxicity to nitrogen dioxide, taking into account its effect on cell membrane and biochemical changes occurring in a person's blood, such as acidosis. Prolonged acidosis, in turn, leads to diseases of the cardiovascular system, hypertension, fatigue and other adverse consequences for the human body.

Residents of a large metropolis are negatively affected by elevated levels of carbon dioxide from morning to evening. First, in crowded public transport and in their own cars, which are stuck in traffic jams for a long time. Then at work, where it is often stuffy and there is nothing to breathe.

It is very important to maintain good air quality in the bedroom as people spend a third of their lives there. In order to get a good night's sleep, the quality of the air in the bedroom is much more important than the duration of sleep, and the level of carbon dioxide in bedrooms and children's rooms should be below 0.08%. High level CO2 in these rooms can cause symptoms such as nasal congestion, throat and eye irritation, headaches and insomnia.

Finnish scientists have found a way to solve this problem based on the axiom that if the level of carbon dioxide in nature is 0.035-0.04%, then indoors it should be close to this level. The device they invented removes excess carbon dioxide from indoor air. The principle is based on the absorption (absorption) of carbon dioxide by a special substance.

carbon dioxide in water

Carbon dioxide somewhat changes the acid-base environment. This is bad for the human body. The fact is that any process in our body occurs at a certain acidity, which corresponds to almost pure water. The presence of carbon dioxide changes it greatly, which somewhat changes our biochemical processes. This is also reflected in the taste properties (sour taste), which leads to unpleasant sensations.

Thus, medicine all over the world has been dealing with this issue for many years, which has led to the emergence of some contraindications to the consumption of carbonated water in any form.

Firstly, any chronic diseases of the gastrointestinal tract completely prohibit the use of carbonated water. The fact is that when drinking such water, irritation of the mucous membrane occurs, which leads to an exacerbation of many inflammatory processes. Most often, doctors prescribe mineral water for treatment, but do not forget that it is imperative to drink it only after removing carbon dioxide.

Secondly, children who are under three years old should not be given such drinks, because their body has not yet formed sufficiently, which means that a metabolic disorder in their body is possible.

Thirdly, individual allergic reactions to carbon dioxide are quite common among people, which means that you need to significantly reduce the amount of carbonated water.

Fourthly, overweight also obliges you to exclude carbonated drinks from your diet, because most often it is due to improper metabolism, which can be worsened by carbon dioxide.

According to the legislation of European countries, the presence of carbon dioxide should not exceed four tenths of a percent. This will give an excellent preservative effect,

but it will not affect the human body, which will give best quality water. An exception is given only to natural mineral water, which may contain a slightly higher amount of gas.