I would like to summarize the information about the principles of diving in terms of breathing gases in the format of keynotes, i.e. when understanding a few principles eliminates the need to remember many facts.

So, breathing under water requires gas. As the simplest option - air supply, which is a mixture of oxygen (∼21%), nitrogen (∼78%) and other gases (∼1%).

Pressure is the main factor. environment. Of all possible pressure units, we will use "absolute technical atmosphere" or ATA. The pressure on the surface is ∼1 ATA, every 10 meters of immersion in water add ∼1 ATA to it.

For further analysis, it is important to understand what partial pressure is, i.e. pressure of a single component of the gas mixture. The total pressure of a gas mixture is the sum of the partial pressures of its components. Partial pressure and the dissolution of gases in liquids are described by Dalton's laws and are most directly related to diving, because a person is mostly liquid. Although the partial pressure is proportional to the molar ratio of the gases in the mixture, for air, the partial pressure can be read by volume or weight concentration, the error will be less than 10%.

When diving, the pressure affects us all-encompassing. The regulator maintains the air pressure in the breathing system, approximately equal to the ambient pressure, less than exactly as much as is necessary for "inhalation". So, at a depth of 10 meters, the air inhaled from the balloon has a pressure of about 2 ATA. A similar absolute pressure will be observed throughout our body. Thus, the partial pressure of oxygen at this depth will be ∼0.42 ATA, nitrogen ∼1.56 ATA

The impact of pressure on the body is the following key factors.

1. Mechanical impact on organs and systems

We will not consider it in detail, in short - the human body has a number of air-filled cavities and a sharp change in pressure in any direction causes a load on tissues, membranes and organs up to mechanical damage - barotrauma.

2. Saturation of tissues with gases

When diving (increasing pressure), the partial pressure of gases in the respiratory tract is higher than in the tissues. Thus, gases saturate the blood, and through the bloodstream, all tissues of the body are saturated. The saturation rate is different for different tissues and is characterized by a “half-saturation period”, i.e. the time during which, at a constant gas pressure, the difference between the partial pressures of the gas and tissues is halved. The reverse process is called "desaturation", it occurs during ascent (decrease in pressure). In this case, the partial pressure of gases in the tissues is higher than the pressure in the gases in the lungs, the reverse process takes place - gas is released from the blood in the lungs, blood with an already lower partial pressure circulates through the body, gases pass from the tissues into the blood and again in a circle. Gas is always moving away from more partial pressure to the smaller one.

It is fundamentally important that different gases have different rates of saturation/desaturation due to their physical properties.

The solubility of gases in liquids is the greater, the higher the pressure. If the amount of dissolved gas is greater than the solubility limit at a given pressure, gas is released, including concentration in the form of bubbles. We see this every time we open a bottle of sparkling water. Since the rate of gas removal (tissue desaturation) is limited by physical laws and gas exchange through the blood, a too rapid pressure drop (rapid ascent) can lead to the formation of gas bubbles directly in the tissues, vessels and cavities of the body, disrupting its work up to death. If the pressure drops slowly, then the body has time to remove the "extra" gas due to the difference in partial pressures.

To calculate these processes, mathematical models of body tissues are used, the most popular is the Albert Buhlmann model, which takes into account 16 types of tissues (compartments) with a half-saturation / half-saturation time from 4 to 635 minutes.

The greatest danger is the inert gas, which has the highest absolute pressure, most often it is nitrogen, which forms the basis of air and does not participate in metabolism. For this reason, the main calculations in mass diving are carried out on nitrogen, since. the effect of oxygen in terms of saturation is orders of magnitude less, while the concept of “nitrogen load” is used, i.e. the residual amount of nitrogen dissolved in the tissues.

Thus, tissue saturation depends on the composition of the gas mixture, pressure and duration of its exposure. For the initial levels of diving, there are restrictions on the depth, duration of the dive and the minimum time between dives, which obviously do not allow under any conditions the saturation of tissues to dangerous levels, i.e. no decompression dives, and even then it is customary to perform "safety stops".

"Advanced" divers use dive computers that dynamically calculate saturation from models depending on gas and pressure, including calculating a "compression ceiling" - the depth above which it is potentially dangerous to ascend based on current saturation. During difficult dives, computers are duplicated, not to mention the fact that single dives are usually not practiced.

3. Biochemical effects of gases

Our body is maximally adapted to air at atmospheric pressure. With increasing pressure, gases that are not even involved in metabolism affect the body in a variety of ways, while the effect depends on the partial pressure of a particular gas. Each gas has its own safety limits.

Oxygen

As a key player in our metabolism, oxygen is the only gas that has not only an upper but also a lower safety limit.

The normal partial pressure of oxygen is ∼0.21 ATA. The need for oxygen strongly depends on the state of the body and physical activity, the theoretical minimum level required to maintain the vital activity of a healthy organism in a state of complete rest is estimated at ∼0.08 ATA, the practical one is ∼0.14 ATA. A decrease in oxygen levels from “nominal” first of all affects the ability to physical activity and can cause hypoxia, or oxygen starvation.

At the same time, a high partial pressure of oxygen causes a wide range of negative consequences - oxygen poisoning or hyperoxia. Of particular danger when diving is its convulsive form, which is expressed in damage to the nervous system, convulsions, which entails the risk of drowning.

For practical purposes, diving is considered to be a safety limit of ∼1.4 ATA, a moderate risk limit is ∼1.6 ATA. At a pressure above ∼2.4 ATA for a long time, the probability of oxygen poisoning tends to unity.

Thus, by simply dividing the limiting oxygen level of 1.4 ATA by the partial pressure of oxygen in the mixture, one can determine the maximum safe pressure of the environment and establish that it is absolutely safe to breathe pure oxygen (100%, 1 ATA) at depths up to ∼4 meters (!! !), compressed air (21%, 0.21 ATA) - up to ∼57 meters, standard "Nitrox-32" with an oxygen content of 32% (0.32 ATA) - up to ∼34 meters. Similarly, you can calculate the limits for moderate risk.

They say that it is this phenomenon that owes its name to "nitrox", since initially this word denoted respiratory gases with lowered oxygen content for working at great depths, "nitrogen enriched", and only then it began to be deciphered as "nitrogen-oxygen" and designate mixtures with elevated oxygen content.

It must be taken into account that an increased partial pressure of oxygen in any case has an effect on the nervous system and lungs, and this different types impact. In addition, the effect tends to accumulate over a series of dives. To take into account the impact on the central nervous system, the concept of "oxygen limit" is used as a unit of account, with the help of which safe limits for single and daily exposure are determined. Detailed tables and calculations can be found.

In addition, increased oxygen pressure negatively affects the lungs, to account for this phenomenon, “oxygen endurance units” are used, which are calculated according to special tables correlating the partial pressure of oxygen and the number of “units per minute”. For example, 1.2 ATA gives us 1.32 OTU per minute. The recognized safety limit is 1425 units per day.

From the foregoing, in particular, it should be clear that a safe stay at great depths requires a mixture with a reduced oxygen content, which is unbreathable at a lower pressure. For example, at a depth of 100 meters (11 ATA), the concentration of oxygen in the mixture should not exceed 12%, and in practice it will be even lower. It is impossible to breathe such a mixture on the surface.

Nitrogen

Nitrogen is not metabolized by the body and has no lower limit. With increased pressure, nitrogen has a toxic effect on the nervous system, similar to narcotic or alcohol intoxication known as "nitrogen narcosis".

The mechanisms of action are not exactly clarified, the boundaries of the effect are purely individual, and depend both on the characteristics of the organism and on its condition. So, it is known that it enhances the effect of fatigue, hangover, all kinds of depressed state of the body such as colds, etc.

Minor manifestations in the form of a state comparable to mild intoxication are possible at any depth, the empirical “martini rule” applies, according to which nitrogen exposure is comparable to a glass of dry martini on an empty stomach for every 10 meters of depth, which is not dangerous and adds good mood. The nitrogen accumulated during regular diving also affects the psyche akin to soft drugs and alcohol, to which the author himself is a witness and participant. It manifests itself in vivid and "narcotic" dreams, in particular, it acts within a few hours. And yes, divers are a bit of drug addicts. Nitrogen.

The danger is represented by strong manifestations, which are characterized by a rapid increase up to a complete loss of adequacy, orientation in space and time, hallucinations, which can lead to death. A person can easily rush to the depths, because it’s cool there or he allegedly saw something there, forget that he is under water and “breathe full chest”, spitting out the mouthpiece, etc. In itself, exposure to nitrogen is not lethal or even harmful, but the consequences under diving conditions can be tragic. It is characteristic that with a decrease in pressure, these manifestations pass just as quickly, sometimes it is enough to rise only 2..3 meters to “sober up sharply”.

Probability of severe manifestation at recreational diving depths entry level(up to 18 m, ∼2.2 ATA) is rated as very low. According to available statistics, cases of severe poisoning become quite probable from 30 meters of depth (∼3.2 ATA), and then the probability increases as pressure increases. At the same time, people with individual stability may not experience problems at much greater depths.

The only way to counteract is constant self-monitoring and control of a partner with an immediate decrease in depth in case of suspected nitrogen poisoning. The use of "nitrox" reduces the likelihood of nitrogen poisoning, of course, within the limits of depth due to oxygen.

Helium and other gases

In technical and professional diving, other gases are also used, in particular, helium. Examples of the use of hydrogen and even neon in deep mixtures are known. These gases are characterized by a high rate of saturation/desaturation, the poisoning effects of helium are observed at pressures above 12 ATA and can be, paradoxically, compensated by nitrogen. However wide application they do not have due to the high cost, so it is virtually impossible for an average diver to encounter them, and if the reader is really interested in such questions, then he already needs to use professional literature, and not this modest review.

When using any mixtures, the calculation logic remains the same as described above, only gas-specific limits and parameters are used, and for deep technical dives, several different compositions are usually used: for breathing on the way down, work at the bottom and a staged way up with decompression, the compositions of these gases are optimized based on the logic of their movement in the body described above.

Practical conclusion

Understanding these theses makes it possible to give meaning to many of the restrictions and rules given in the courses, which is absolutely necessary both for further development and for their correct violation.

Nitrox is recommended for use in normal diving because it reduces the nitrogen load on the body even if you stay completely within the limits of recreational diving, this is a better feeling, more fun, less consequences. However, if you are going to dive deep and often, you need to remember not only about its benefits, but also about possible oxygen intoxication. Always personally check oxygen levels and determine your limits.

Nitrogen poisoning is the most likely problem you may encounter, always be considerate of yourself and your partner.

Separately, I would like to draw attention to the fact that reading this text does not mean that the reader has mastered the full set of information for understanding the work with gases during difficult dives. For practical application this is completely insufficient. This is just a starting point and a basic understanding, nothing more.

PaO2, along with two other quantities (paCO2 and pH), make up such a concept as "blood gases" (Arterial blood gases - ABG (s)). The value of paO2 depends on many parameters, the main of which are the age and height of the patient (partial pressure of O2 in atmospheric air). Thus, pO2 must be interpreted individually for each patient.
Accurate results for ABGs depend on the collection, processing, and actual analysis of the sample. Clinically important errors can occur at any of these steps, but blood gas measurements are particularly vulnerable to errors that occur prior to analysis. The most common problems include
- sampling of non-arterial (mixed or venous) blood;
- the presence of air bubbles in the sample;
- insufficient or excessive amount of anticoagulant in the sample;
- delaying the analysis and keeping the sample uncooled all this time.

A proper blood sample for ABG analysis typically contains 1-3 ml of arterial blood drawn anaerobically from a peripheral artery into a special plastic container using a small diameter needle. Air bubbles that may enter during sampling must be removed immediately. The air in the room has a paO2 of about 150 mmHg. (at sea level) and paCO2 is practically equal to zero. Thus, air bubbles that mix with arterial blood shift (increase) paO2 to 150 mm Hg. and reduce (decrease) paCO2.

If heparin is used as an anticoagulant and the sampling is done with a syringe and not with a special container, the pH of heparin, which is approximately 7.0, should be taken into account. Thus, an excess of heparin can change all three ABG values ​​(paO2, paCO2, pH). A very small amount of heparin is needed to prevent clotting; 0.05 - 0.10 ml of a dilute solution of heparin (1000 IU / ml) will counteract the clotting of approximately 1 ml of blood without affecting pH, paO2, paCO2. After flushing the syringe with heparin, a sufficient amount of heparin usually remains in the dead space of the syringe and needle, which is enough to anticoagulate without distorting the ABG values.

After collection, the sample should be analyzed as soon as possible. If a delay of more than 10 minutes occurs, the sample must be immersed in a container with ice. Leukocytes and platelets continue to consume oxygen in the sample after collection, and can cause a significant drop in paO2 when stored for long periods at room temperature, especially under conditions of leukocytosis or thrombocytosis. Cooling will prevent any clinical important changes, for at least 1 hour, by reducing the metabolic activity of these cells.

The partial pressure or tension of carbon dioxide (pCO2) is the pressure of CO2 in a gas mixture in equilibrium with arterial blood plasma at a temperature of 38°C. The indicator is a criterion for the concentration of carbon dioxide in the blood.

The change in pCO2 plays a leading role in respiratory disorders of the acid-base state (respiratory acidosis and respiratory alkalosis)

In respiratory acidosis, pCO2 increases due to a violation of lung ventilation, which causes the accumulation of carbonic acid,

In respiratory alkalosis, pCO2 decreases as a result of hyperventilation of the lungs, which leads to increased excretion of carbon dioxide from the body and alkalization of the blood.

With non-respiratory (metabolic) azidoses / alkalosis, the pCO2 indicator does not change.
If there are such shifts in pH and the pCO2 index is not normal, then there are secondary (or compensatory) changes.
When clinically evaluating a shift in pCO2, it is important to establish whether the changes are causal or compensatory!

Thus, an increase in pCO2 occurs with respiratory acidosis and compensated metabolic alkalosis, and a decrease occurs with respiratory alkalosis and compensation of metabolic acidosis.

Fluctuations in the value of pCO2 in pathological conditions are in the range from 10 to 130 mm Hg.

With respiratory disorders, the direction of the shift in the blood pH value is opposite to the pCO2 shift, with metabolic disorders, the shifts are unidirectional.

Bicarbonate ion concentration

The concentration of bicarbonates (HCO3- ions) in the blood plasma is the third main indicator of the acid-base state.

In practice, there are indicators of actual (true) bicarbonates and standard bicarbonates.

Actual bicarbonate (AB, AB) is the concentration of HCO3– ions in the test blood at 38°C and actual pH and pCO2 values.

Standard bicarbonates (SB, SB) is the concentration of HCO3– ions in the test blood when it is brought to standard conditions: full blood oxygen saturation, equilibrated at 38°C with a gas mixture in which pCO2 is 40 mmHg.

In healthy people, the concentration of topical and standard bicarbonates is almost the same.

The diagnostic value of the concentration of bicarbonates in the blood is, first of all, in determining the nature of the violations of the acid-base state (metabolic or respiratory).

The indicator primarily changes with metabolic disorders:

With metabolic acidosis, the HCO3– index decreases, because. spent on the neutralization of acidic substances (buffer system)

With metabolic alkalosis - increased

Since carbonic acid dissociates very poorly and its accumulation in the blood has practically no effect on the concentration of HCO3–, the change in bicarbonates in primary respiratory disorders is small.

When metabolic alkalosis is compensated, bicarbonates accumulate due to a decrease in respiration, and when metabolic acidosis is compensated, as a result of increased renal reabsorption.

Buffer Base Concentration

Another indicator characterizing the state of the acid-base state is the concentration of buffer bases (buffer bases, BB), which reflects the sum of all anions in whole blood, mainly bicarbonate and chlorine anions, other anions include protein ions, sulfates, phosphates, lactate, ketone body, etc.

This parameter is almost independent of changes in the partial pressure of carbon dioxide in the blood, but reflects the production of acids by tissues and partly the function of the kidneys.

By the value of the buffer bases, one can judge the shifts in the acid-base state associated with an increase or decrease in the content of non-volatile acids in the blood (that is, all but carbonic acid).

In practice, the parameter used for the concentration of buffer bases is the parameter "residual anions" or "undetectable anions" or "anion mismatch" or "anion difference".

The use of the anion difference index is based on the postulate of electrical neutrality, i.e. the number of negative (anions) and positive (cations) in the blood plasma should be the same.
If we experimentally determine the amount of Na+, K+, Cl–, HCO3– ions most represented in blood plasma, then the difference between cations and anions is approximately 12 mmol/l.

An increase in the anion gap indicates the accumulation of unmeasured anions (lactate, ketone bodies) or cations, which is specified by the clinical picture or by history.

Indicators of total buffer bases and anion gap are especially informative in case of metabolic shifts in the acid-base state, while in case of respiratory disorders, its fluctuations are insignificant.

Excess buffer bases

Base excess (BE, IO) - the difference between the actual and due values ​​of buffer bases.
By value, the indicator can be positive (excess of bases) or negative (deficit of bases, excess of acids).

The indicator of diagnostic value is higher than the concentrations of topical and standard bicarbonates. Base excess reflects shifts in the number of bases in blood buffer systems, while actual bicarbonate only reflects concentration.

The greatest changes in the indicator are noted in metabolic disorders: in acidosis, a lack of blood bases is detected (deficit of bases, negative values), in alkalosis, an excess of bases (positive values).
Deficiency limit compatible with life, 30 mmol/l.

With respiratory shifts, the indicator changes slightly.

The pH value forms the activity of cells

Acid-base balance is a state that is provided by physiological and physico-chemical processes that make up a functionally unified system for stabilizing the concentration of H + ions.
The normal concentration of H+ ions is about 40 nmol/l, which is 106 times less than the concentration of many other substances (glucose, lipids, minerals).

H+ ion concentration fluctuations compatible with life range from 16-160 nmol/l.

Since metabolic reactions are often associated with the oxidation and reduction of molecules, these reactions necessarily involve compounds that act as an acceptor or donor of hydrogen ions. The participation of other compounds is reduced to ensuring the constancy of the concentration of hydrogen ions in biological fluids.

The stability of the intracellular concentration of H + is necessary for:

Optimal activity of enzymes in membranes, cytoplasm and intracellular organelles

Formation of the electrochemical gradient of the mitochondrial membrane at the proper level and sufficient production of ATP in the cell.

Shifts in the concentration of H+ ions lead to changes in the activity of intracellular enzymes, even within the limits of physiological values.
For example, gluconeogenesis enzymes in the liver are more active when the cytoplasm is acidified, which is important during starvation or muscle exercise, glycolysis enzymes are more active at normal pH.

The stability of the extracellular concentration of H+ ions provides:

Optimal functional activity of blood plasma proteins and intercellular space (enzymes, transport proteins),

Solubility of inorganic and organic molecules,

Nonspecific protection of the skin epithelium,

Negative charge on the outer surface of the erythrocyte membrane.

When the concentration of H+ ions in the blood changes, the compensatory activity of two major body systems is activated:

1. Chemical compensation system

The action of extracellular and intracellular buffer systems,

Intensity of intracellular formation of H+ and HCO3– ions.

2. Physiological compensation system

Pulmonary ventilation and CO2 removal,

Renal excretion of H+ ions (acidogenesis, ammoniumgenesis), reabsorption and synthesis of HCO3–.

A decrease in the partial pressure of oxygen in the inhaled air leads to an even lower level in the alveoli and outflowing blood. If the inhabitants of the plains climb the mountains, hypoxia increases their lung ventilation by stimulating arterial chemoreceptors. The body reacts with adaptive reactions, the purpose of which is to improve the provision of tissues with O 2. Changes in respiration during high-altitude hypoxia in different people different. The reactions of external respiration arising in all cases are determined by a number of factors: 1) the rate at which hypoxia develops; 2) the degree of consumption of O 2 (rest or physical activity); 3) the duration of hypoxic exposure.

The most important compensatory response to hypoxia is hyperventilation. The initial hypoxic stimulation of respiration, which occurs when ascending to a height, leads to leaching of CO 2 from the blood and the development of respiratory alkalosis. This in turn causes an increase in the pH of the extracellular fluid of the brain. Central chemoreceptors respond to such a shift in pH in the cerebrospinal fluid by a sharp decrease in their activity, which inhibits the neurons of the respiratory center to such an extent that it becomes insensitive to stimuli emanating from peripheral chemoreceptors. Quite quickly, hyperpnea is replaced by involuntary hypoventilation, despite persistent hypoxemia. Such a decrease in the function of the respiratory center increases the degree of hypoxic state of the body, which is extremely dangerous, primarily for the neurons of the cerebral cortex.

With acclimatization to high altitude conditions, adaptation occurs physiological mechanisms to hypoxia. After staying for several days or weeks at altitude, as a rule, respiratory alkalosis is compensated by the excretion of HCO 3 by the kidneys, due to which part of the inhibitory effect on alveolar hyperventilation falls out and hyperventilation intensifies. Acclimatization also causes an increase in hemoglobin concentration due to increased hypoxic stimulation of erythropoietins by the kidneys. So, among the inhabitants of the Andes, constantly living at an altitude of 5000 m, the concentration of hemoglobin in the blood is 200 g / l. The main means of adaptation to hypoxia are: 1) a significant increase in pulmonary ventilation; 2) an increase in the number of red blood cells; 3) an increase in the diffusion capacity of the lungs; 4) increased vascularization of peripheral tissues; 5) an increase in the ability of tissue cells to use oxygen, despite the low pO 2 .

Some people develop an acute pathological condition when they rise rapidly to high altitude ( acute mountain sickness and high-altitude pulmonary edema). Since of all the organs of the central nervous system it has the highest sensitivity to hypoxia, when climbing to high altitudes, neurological disorders primarily occur. When climbing to a height, symptoms such as headache, fatigue, nausea. Pulmonary edema often occurs. Below 4500 m, such severe disturbances occur less frequently, although minor functional abnormalities occur. Depending on the individual characteristics of the organism and its ability to acclimatize, a person is able to reach great heights.

test questions

1. How do the parameters of barometric pressure and partial pressure of oxygen change with increasing altitude?

2. What adaptive reactions occur when climbing to a height?

3. How is acclimatization to the conditions of the highlands?

4. How is acute mountain sickness manifested?

Breathing while diving

During underwater work, the diver breathes at a pressure higher than atmospheric pressure by 1 atm. for every 10 m dive. About 4/5 of air is nitrogen. At sea level nitrogen has no significant effect on the body, but at high pressure it can cause varying degrees of narcosis. The first signs of moderate anesthesia appear at a depth of about 37 m if the diver remains at depth for an hour or more and breathes compressed air. With a long stay at a depth of more than 76 m (8.5 atm pressure), nitrogen narcosis usually develops, the manifestations of which are similar to alcohol intoxication. If a person inhales the air of the usual composition, then nitrogen dissolves in adipose tissue. Diffusion of nitrogen from tissues is slow, so the rise of the diver to the surface must be carried out very slowly. Otherwise, intravascular formation of nitrogen bubbles is possible (the blood "boils") with severe damage to the central nervous system, organs of vision, hearing, and severe pain in the joints. There is a so-called decompression sickness. For treatment, the victim must be re-placed in an environment with high pressure. Gradual decompression can last several hours or days.

The likelihood of decompression sickness can be significantly reduced by breathing special gas mixtures, such as an oxygen-helium mixture. This is due to the fact that the solubility of helium is less than nitrogen, and it diffuses faster from tissues, since its molecular weight is 7 times less than that of nitrogen. In addition, this mixture has a lower density, so the work expended on external respiration is reduced.

test questions

5. How do the parameters of barometric pressure and partial pressure of oxygen change with increasing altitude above sea level?

6. What adaptive reactions occur when climbing to a height?

7. How is acclimatization to the conditions of the highlands?

8. How does acute mountain sickness manifest itself?

7.3 Test tasks and situational task

Choose one correct answer.

41. IF A PERSON DIVES WITHOUT SPECIAL EQUIPMENT WITH PRELIMINARY HYPERVENTILATION THE CAUSE OF SUDDEN CONSCIOUSNESS MAY BE PROGRESSIVE

1) asphyxia

2) hypoxia

3) hyperoxia

4) hypercapnia

42. WHEN DIVING UNDER WATER WITH A MASK AND Snorkel, IT IS NOT POSSIBLE TO INCREASE THE LENGTH OF THE STANDARD TUBE (30-35 cm) DUE TO

1) the occurrence of a pressure gradient between air pressure in the alveoli and water pressure on the chest

2) the danger of hypercapnia

3) the danger of hypoxia

4) increase in the volume of dead space

Case study 8

Diving champions dive to a depth of up to 100 m without scuba gear and return to the surface in 4-5 minutes. Why don't they get decompression sickness?

8. Sample answers to test tasks and situational tasks

Sample answers to test tasks:

Sample answers to situational tasks:

Solution of situational problem No. 1:

If we are talking about natural breathing, then the first one is right. The mechanism of respiration is suction. But, if we mean artificial respiration, then the second one is right, since here the mechanism is forced.

Solution of situational problem No. 2:

For effective gas exchange, a certain relationship between ventilation and blood flow in the vessels of the lungs is necessary. Therefore, these people had differences in blood flow values.

Solution of situational problem No. 3:

In the blood, oxygen exists in two states: physically dissolved and bound to hemoglobin. If hemoglobin does not work well, then only dissolved oxygen remains. But there is very little of it. So it is necessary to increase its quantity. This is achieved by hyperbaric oxygen therapy (the patient is placed in a chamber with high oxygen pressure).

Solution of situational problem No. 4:

Malate is oxidized by the NAD-dependent enzyme malate dehydrogenase (mitochondrial fraction). Moreover, when one malate molecule is oxidized, one NADH H + molecule is formed, which enters into complete chain electron transfer to form three ATP molecules from three ADP molecules. As you know, ADP is an activator of the respiratory chain, and ATP is an inhibitor. ADP in relation to malate is taken obviously in short supply. This leads to the fact that the activator (ADP) disappears from the system and the inhibitor (ATP) appears, which, in turn, leads to the stop of the respiratory chain and the absorption of oxygen. Hexokinase catalyzes the transfer of a phosphate group from ATP to glucose to form glucose-6-phosphate and ADP. Thus, during the work of this enzyme, the inhibitor (ATP) is consumed in the system and the activator (ADP) appears, so the respiratory chain resumed work.

Solution of situational problem No. 5:

The enzyme succinate dehydrogenase, which catalyzes the oxidation of succinate, belongs to FAD-dependent dehydrogenases. As is known, FADH 2 ensures the entry of hydrogen into a shortened electron transport chain, during which 2 ATP molecules are formed. Amobarbital blocks the respiratory chain at the level of the 1st conjugation of respiration and phosphorylation and does not affect the oxidation of succinate.

Solution of situational problem No. 6:

With a very slow clamping of the umbilical cord, accordingly, the content of carbon dioxide in the blood will increase very slowly and the neurons of the respiratory center will not be able to be excited. The first breath never happens.

Solution of situational problem No. 7:

The leading role in the excitation of the neurons of the respiratory center is played by carbon dioxide. In the agonal state, the excitability of the neurons of the respiratory center is sharply reduced and therefore they cannot be excited by the action of ordinary amounts of carbon dioxide. After several respiratory cycles, there is a pause, during which significant amounts of carbon dioxide accumulate. Now they can already excite the respiratory center. There are several breaths, the amount of carbon dioxide decreases, there is a pause again, and so on. If it is not possible to improve the patient's condition, a fatal outcome is inevitable.

Solution of situational problem No. 8:

A diver at great depths breathes air under high pressure. Therefore, the solubility of gases in the blood increases significantly. Nitrogen in the body is not consumed. Therefore, with a rapid rise, its increased pressure quickly decreases, and it is rapidly released from the blood in the form of bubbles, which leads to an embolism. The diver does not breathe at all during the dive. With a quick rise, nothing terrible happens.

Attachment 1

Table 1

Name of indicators of pulmonary ventilation in Russian and English

Name of the indicator in Russian	Accepted abbreviation	The name of the indicator for English language	Accepted abbreviation
Vital capacity of the lungs	VC	Vital capacity	VC
Tidal volume	BEFORE	Tidal volume	TV
Inspiratory reserve volume	ROVD	inspiratory reserve volume	IRV
expiratory reserve volume	ROvyd	Expiratory reserve volume	ERV
Maximum ventilation	MVL	Maximal voluntary ventilation	MW
forced vital capacity	FZhEL	forced vital capacity	FVC
Forced expiratory volume in the first second	FEV1	Forced expiration volume 1 sec	FEV1
Tiffno index	IT, or FEV1/VC %		FEV1% = FEV1/VC%
Maximum expiratory flow rate 25% FVC remaining in the lungs	MOS25	Maximal expiratory flow 25% FVC	MEF25
	Forced expiratory flow 75% FVC	FEF75
Maximum expiratory flow rate 50% of FVC remaining in the lungs	MOS50	Maximal expiratory flow 50% FVC	MEF50
	Forced expiratory flow 50% FVC	FEF50
Maximum expiratory flow rate 75% of FVC remaining in the lungs	MOS75	Maximal expiratory flow 75% FVC	MEF75
	Forced expiratory flow 25% FVC	FEF25
Average expiratory flow rate in the range from 25% to 75% FVC	SOS25-75	Maximal expiratory flow 25-75% FVC	MEF25-75
	Forced expiratory flow 25-75% FVC	FEF25-75

Annex 2

BASIC RESPIRATORY PARAMETERS

VC (VC = Vital Capacity) - vital capacity of the lungs(the volume of air that leaves the lungs during the deepest exhalation after the deepest breath)

Rovd (IRV = inspiratory reserve volume) - inspiratory reserve volume(additional air) is the volume of air that can be inhaled at maximum inhalation after a normal inhalation

ROvyd (ERV = Expiratory Reserve Volume) - expiratory reserve volume(reserve air) is the volume of air that can be exhaled at maximum exhalation after a normal exhalation

EB (IC = inspiratory capacity) - inspiratory capacity- the actual sum of tidal volume and inspiratory reserve volume (EV = DO + RVD)

FOEL (FRC = functional residual capacity) - functional residual lung capacity. This is the volume of air in the lungs of a patient at rest, in a position where normal exhalation is completed and the glottis is open. FOEL is the sum of the expiratory reserve volume and residual air (FOEL = ROvyd + RH). This parameter can be measured using one of two methods: helium dilution or body plethysmography. Spirometry does not measure FOEL, so the value of this parameter must be entered manually.

RH (RV = residual volume) - residual air(another name - OOL, residual volume of the lungs) is the volume of air that remains in the lungs after maximum exhalation. Residual volume cannot be determined by spirometry alone; this requires additional lung volume measurements (using the helium dilution method or body plethysmography).

TLC (TLC = total lung capacity) - total lung capacity(the volume of air in the lungs after the deepest possible breath). HR = VC + OB

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., to 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 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 partial pressure of gases in the 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 other gases (nitrogen, oxygen, carbon dioxide) is no longer 700 mm, but 700-47 - 713 mm. With an oxygen content in the alveolar air equal to 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 a 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 the 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 that enters or leaves 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 whose pressure differs sharply from the pressure of the gases in the liquid, then large quantities of gas may escape from or enter into the latter. On the contrary, if a sufficiently large volume of liquid is in 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 practically not change.

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 in millimeters of mercury or water column. If the gas pressure is 1.00 mm Hg. Art., this means that the gas dissolved in the liquid is in equilibrium with the free gas under 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 again become equal to each other. For example, if the oxygen pressure 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 tension of oxygen in the liquid will be dismissed, and its pressure outside the liquid will decrease until a new dynamic equilibrium is established and both of these values ​​are equal, having received some new value between 150 and 100 mm. How the pressure and stress change in a given study depends on the relative volumes of gas and liquid.