MOSCOW, December 25 - RIA Novosti, Tatyana Pichugina. Since the Foundation for Advanced Study (FPI) approved the liquid breathing project in 2016, the public has been keenly interested in its success. A recent demonstration of the capabilities of this technology literally blew up the Internet. At a meeting between Deputy Prime Minister Dmitry Rogozin and Serbian President Aleksandar Vucic, the dachshund was immersed for two minutes in an aquarium with a special liquid saturated with oxygen. After the procedure, the dog, according to the Deputy Prime Minister, is alive and well. What was this liquid?
"Scientists have synthesized substances that do not exist in nature - perfluorocarbons, in which intermolecular forces are so small that they are considered something intermediate between a liquid and a gas. They dissolve oxygen in themselves 18-20 times more than water," says the doctor of medical sciences Evgeny Mayevsky, Professor, Head of the Laboratory of Energy of Biological Systems of the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences, one of the creators of perftoran, the so-called blue blood. He has been working on medical applications of perfluorocarbons since 1979.
At a partial pressure of one atmosphere, only 2.3 milliliters of oxygen dissolves in 100 milliliters of water. Under the same conditions, perfluorocarbons can contain up to 50 milliliters of oxygen. This makes them potentially breathable.
“For example, when diving to a depth every 10 meters, the pressure increases by at least one atmosphere. As a result, the chest and lungs will shrink to such an extent that it will become impossible to breathe in a gaseous environment. And if there is a gas-carrying liquid in the lungs, of a much higher density than air and even water, they will be able to function. In perfluorocarbons, oxygen can be dissolved without the admixture of nitrogen, which is abundant in the air and whose dissolution in tissues is one of the most significant causes of decompression sickness when lifting from a depth, "continues Mayevsky.
Oxygen will enter the blood from the fluid that fills the lungs. It can also dissolve the carbon dioxide carried in the blood.
The principle of liquid breathing is perfectly mastered by fish. Their gills pass through themselves a colossal volume of water, take away the oxygen dissolved there and give it to the blood. Man has no gills, and all gas exchange takes place through the lungs, whose surface area is about 45 times the surface area of the body. To drive air through them, we inhale and exhale. The respiratory muscles help us with this. Since perfluorocarbons are denser than air, breathing on the surface with their help is very problematic.
"This is the science and art of choosing such perfluorocarbons to facilitate the work of the respiratory muscles and prevent damage to the lungs. Much depends on the duration of the process of breathing liquid, on whether it occurs forcefully or spontaneously," the researcher concludes.
However, there are no fundamental obstacles to a person breathing liquid. Evgeny Mayevsky believes that Russian scientists will bring the demonstrated technology to practical use in the next few years.
From resuscitation to rescue of submariners
Scientists began to consider perfluorocarbons as an alternative to breathing gas mixtures in the middle of the last century. In 1962, the Dutch researcher Johannes Kylstra published "Of mice as fish", which describes an experiment with a rodent placed in an oxygenated saline solution at a pressure of 160 atmospheres. The animal remained alive for 18 hours. Then Kilstra began experimenting with perfluorocarbons, and already in 1966 at the Cleveland Children's Hospital (USA), physiologist Leland C. Clark tried to use them to improve the breathing of newborns with cystic fibrosis. This is a genetic disease in which a child is born with underdeveloped lungs, his alveoli collapse, which prevents breathing. The lungs of such patients are flushed with oxygenated saline. Clark decided it was better to do it with an oxygen-containing liquid. This researcher subsequently did a lot for the development of liquid breathing.
© 20th Century Fox Film CorporationShot from the movie "The Abyss"
© 20th Century Fox Film Corporation
In the early 1970s, the USSR became interested in "breathing" fluid, largely due to the head of the laboratory of the Leningrad Research Institute of Blood Transfusion, Zoya Aleksandrovna Chaplygina. This institute became one of the leaders in the project to create blood substitutes - oxygen carriers based on emulsions of perfluorocarbons and solutions of modified hemoglobin.
Felix Beloyartsev and Khalid Khapiy actively worked on the use of these substances for washing the lungs at the Institute of Cardiovascular Surgery.
“In our experiments, the lungs of small animals suffered somewhat, but they all survived,” recalls Evgeny Mayevsky.
The breathing system with the help of liquid was developed on a closed topic at the institutes of Leningrad and Moscow, and since 2008 - at the Department of Aerohydrodynamics of the Samara State Aerospace University. They made a capsule of the "Mermaid" type for practicing liquid breathing in case of emergency rescue of divers from great depths. Since 2015, the development has been tested in Sevastopol on the Terek theme, supported by the FPI.
Legacy of the nuclear project
Perfluorocarbons (perfluorocarbons) are organic compounds where all hydrogen atoms are replaced by fluorine atoms. This is emphasized by the Latin prefix "per-", meaning completeness, integrity. These substances are not found in nature. They tried to synthesize them at the end of the 19th century, but they really succeeded only after the Second World War, when they were needed for the nuclear industry. Their production in the USSR was established by Academician Ivan Ludwigovich Knunyants, the founder of the laboratory of organofluorine compounds at the Institute of Economics of the Russian Academy of Sciences.
"Perfluorocarbons were used in the technology for obtaining enriched uranium. In the USSR, the State Institute of Applied Chemistry in Leningrad was their largest developer. Currently, they are produced in Kirovo-Chepetsk and Perm," Mayevsky says.
Externally, liquid perfluorocarbons look like water, but are noticeably denser. They do not react with alkalis and acids, do not oxidize, and decompose at temperatures above 600 degrees. In fact, they are considered chemically inert compounds. Due to these properties, perfluorocarbon materials are used in resuscitation and regenerative medicine.
"There is such an operation - bronchial lavage, when a person under anesthesia is washed with one lung, and then another. In the early 80s, together with the Volgograd surgeon A.P. Savin, we came to the conclusion that this procedure is best done with perfluorocarbon in the form of an emulsion," - Evgeny Mayevsky gives an example.
These substances are actively used in ophthalmology, to accelerate wound healing, in the diagnosis of diseases, including cancer. In recent years, the method of NMR diagnostics using perfluorocarbons has been developed abroad. In our country, these studies are successfully carried out by a team of scientists from Moscow State University. M. V. Lomonosov under the guidance of Academician Alexei Khokhlov, INEOS, ITEB RAS and IEP (Serpukhov).
It is impossible not to mention the fact that these substances are used to make oils, lubricants for systems operating at high temperatures, including jet engines.
A liquid saturated with dissolved oxygen, which penetrates into the blood. The most suitable substances for this purpose are perfluorocarbon compounds, which dissolve oxygen and carbon dioxide well, have a low surface tension, are highly inert, and are not metabolized in the body.
Partial liquid ventilation of the lungs is currently under clinical trials for various respiratory disorders. Several methods of liquid ventilation of the lungs have been developed, including ventilation using vapors and aerosols of perfluorocarbons.
Full liquid ventilation of the lungs consists in the complete filling of the lungs with liquid. Experiments on complete liquid ventilation of the lungs were carried out on animals in the 70s and 80s of the 20th century in the USSR and the USA, but have not yet left this stage. This is due to the fact that the studied compounds suitable for liquid ventilation of the lungs have a number of disadvantages that significantly limit their applicability. In particular, no methods were found that could be applied continuously.
It is assumed that liquid breathing can be used in deep-sea diving, space flights, as one of the means in the complex therapy of certain diseases.
In culture
Something similar was shown in James Cameron's film The Abyss (touches on the use of a liquid breathing apparatus for ultra-deep diving), and also touched upon in Dan Brown's book The Lost Symbol.
In the finale of Brian de Palma's sci-fi film Mission to Mars, Gary Sinise's hero finds himself aboard a Martian ship, which also shows the use of liquid breathing technology.
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An excerpt characterizing liquid breathing
The prince turned to the steward and stared at him with frowning eyes.- What? Minister? Which minister? Who ordered? he spoke in his piercing, hard voice. - For the princess, my daughter, they didn’t clear it, but for the minister! I don't have ministers!
Your Excellency, I thought...
- You thought! the prince shouted, pronouncing the words more hastily and more incoherently. - You thought ... Robbers! scoundrels! I will teach you to believe, - and, raising a stick, he swung it at Alpatych and would have hit him if the manager had not involuntarily deviated from the blow. - I thought! Scoundrels! he shouted hastily. But, despite the fact that Alpatych, who himself was frightened of his impudence - to deviate from the blow, approached the prince, obediently lowering his bald head in front of him, or, perhaps, precisely because of this, the prince, continuing to shout: “scoundrels! throw up the road!" did not pick up the stick another time and ran into the rooms.
Before dinner, the princess and m lle Bourienne, who knew that the prince was not in a good mood, stood waiting for him: m lle Bourienne with a beaming face that said: “I don’t know anything, I’m the same as always,” and Princess Mary - pale, frightened, with lowered eyes. The hardest thing for Princess Mary was that she knew that in these cases it was necessary to act like m lle Bourime, but she could not do it. It seemed to her: “If I act as if I don’t notice, he will think that I have no sympathy for him; I will make it so that I myself am boring and out of sorts, he will say (as it happened) that I hung my nose, ”etc.
The prince looked at his daughter's frightened face and snorted.
“Dr… or fool!…” he said.
“And that one isn’t! they’ve been gossiping about her, too,” he thought of the little princess, who was not in the dining room.
- Where is the princess? - he asked. - Hiding?...
“She is not quite well,” said m lle Bourienne, smiling cheerfully, “she will not come out. It's so understandable in her position.
- Hm! um! uh! uh! - said the prince and sat down at the table.
The plate seemed to him not clean; he pointed to the stain and dropped it. Tikhon picked it up and handed it to the barman. The little princess was not unwell; but she was so irresistibly afraid of the prince that, hearing how he was in a bad mood, she decided not to go out.
“I am afraid for the child,” she said to m lle Bourienne, “God knows what can be done from fright.
In general, the little princess lived in the Bald Mountains constantly under a feeling of fear and antipathy towards the old prince, which she was not aware of, because fear prevailed so much that she could not feel it. There was also antipathy on the part of the prince, but it was drowned out by contempt. The princess, having settled down in the Bald Mountains, especially fell in love with m lle Bourienne, spent days with her, asked her to spend the night with her, and often spoke with her about her father-in-law and judged him.
- Il nous arrive du monde, mon prince, [Guests are coming to us, prince.] - said m lle Bourienne, unrolling a white napkin with her pink hands. - Son excellence le prince Kouraguine avec son fils, a ce que j "ai entendu dire? [His Excellency Prince Kuragin with his son, how much have I heard?] - she said inquiringly.
“Hm… this excellence boy… I appointed him to the collegium,” the prince said indignantly. - And why the son, I can not understand. Princess Lizaveta Karlovna and Princess Marya may know; I don't know why he's bringing this son here. I don't need. And he looked at the blushing daughter.
- Unhealthy, right? From the fear of the minister, as this blockhead Alpatych said today.
- No, mon pere. [father.]
No matter how unsuccessfully m lle Bourienne got on the subject of conversation, she did not stop and chatted about greenhouses, about the beauty of a new blossoming flower, and the prince softened after the soup.
After dinner he went to his daughter-in-law. The little princess sat at a small table and chatted with Masha, the maid. She turned pale when she saw her father-in-law.
The little princess has changed a lot. She was more bad than good, now. The cheeks drooped, the lip rose up, the eyes were drawn down.
“Yes, some kind of heaviness,” she answered the prince’s question about what she felt.
Scientific research does not stop for a day, progress is on, giving mankind more and more new discoveries. Hundreds of scientists and their assistants are working in the field of studying living beings and synthesizing unusual substances. Entire departments are experimenting, testing various theories, and sometimes the discoveries amaze the imagination - after all, what could only be dreamed of can become a reality. They develop ideas, and questions about freezing a person in a cryochamber with subsequent thawing in a century or about the ability to breathe liquid are not just a fantastic story for them. Their hard work can make these fantasies come true.
Scientists have long been concerned about the question: can a person breathe liquid?
Does a person need liquid breathing
No efforts, no time, no money are spared for such research. And one of these questions that have been worrying the most enlightened minds for decades is as follows - is liquid breathing possible for a person? Will the lungs be able to absorb oxygen not from a special liquid? For those who doubt the real need for this type of breathing, we can give at least 3 promising areas where it will serve a person in good stead. If, of course, they can implement it.
- The first direction is diving to great depths. As you know, when diving, the diver experiences the pressure of the aquatic environment, which is 800 times denser than air. And it increases by 1 atmosphere every 10 meters of depth. Such a sharp increase in pressure is fraught with a very unpleasant effect - the gases dissolved in the blood begin to boil in the form of bubbles. This phenomenon is called "caisson sickness", it often affects those who are actively involved. Also, when swimming in deep waters, there is a risk of getting oxygen or nitrogen poisoning, since in such conditions these gases that are vital to us become very toxic. In order to somehow fight this, they use either special breathing mixtures or rigid spacesuits that maintain a pressure of 1 atmosphere inside themselves. But if liquid breathing were possible, it would become the third, easiest solution to the problem, because the respiratory liquid does not saturate the body with nitrogen and inert gases, and there is no need for long decompression.
- The second way of application is medicine. The use of breathing fluids in it could save the lives of premature babies, because their bronchi are underdeveloped and ventilators can easily damage them. As you know, in the womb, the lungs of the embryo are filled with liquid and by the time of birth, it accumulates pulmonary surfactant - a mixture of substances that does not allow tissues to stick together when breathing air. But with an early birth, breathing requires too much strength from the baby and this can be fatal.
History has a precedent for the use of total fluid ventilation, and it dates back to 1989. It was applied by T. Shaffer, who worked as a pediatrician at Temple University (USA), saving premature babies from death. Alas, the attempt was unsuccessful, three small patients did not survive, but it is worth mentioning that the deaths were caused by other causes, and not by the liquid breathing method itself.
Since then, fully ventilated human lungs have not dared, but in the 90s, patients with severe inflammation were subjected to partial liquid ventilation. In this case, the lungs are only partially filled. Alas, the effectiveness of the method was controversial, since conventional air ventilation worked just as well.
- Application in astronautics. With the current level of technology, an astronaut experiences g-forces up to 10 g during flight. After this threshold, it is impossible to maintain not only working capacity, but also consciousness. Yes, and the load on the body is uneven, and along the fulcrum, which can be excluded when immersed in a liquid, the pressure will spread equally to all points of the body. This principle underlies the design of the rigid Libelle spacesuit, filled with water and allowing the limit to be increased to 15-20 g, and even then because of the limitation of the density of human tissues. And if the astronaut is not only immersed in liquid, but his lungs are also filled with it, then it will be possible for him to easily endure extreme overloads far beyond the 20 g mark. Not infinite, of course, but the threshold will be very high if one condition is met - the liquid in the lungs and around the body must be equal in density to water.
The origin and development of liquid breathing
The very first experiments date back to the 60s of the last century. The first to test the emerging technology of liquid breathing were laboratory mice and rats, forced to breathe not air, but a saline solution, which was under a pressure of 160 atmospheres. And they breathed! But there was a problem that prevented them from surviving in such an environment for a long time - the liquid did not allow carbon dioxide to be removed.
But the experiments didn't stop there. Further, research began on organic substances whose hydrogen atoms were replaced by fluorine atoms - the so-called perfluorocarbons. The results were much better than those of the ancient and primitive liquid, because perfluorocarbon is inert, not absorbed by the body, and perfectly dissolves oxygen and hydrogen. But it was far from perfection and research in this direction continued.
Now the best achievement in this area is perflubron (commercial name - "Liquivent"). The properties of this liquid are amazing:
- The alveoli open better when this fluid enters the lungs and gas exchange improves.
- This liquid can carry 2 times more oxygen compared to air.
- The low boiling point allows it to be removed from the lungs by evaporation.
But our lungs are not designed for completely liquid breathing. If you fill them completely with perflubron, you will need a membrane oxygenator, a heating element and air ventilation. And do not forget that this mixture is 2 times thicker than water. Therefore, mixed ventilation is used, in which the lungs are filled with liquid only by 40%.
But why can't we breathe liquid? All because of carbon dioxide, which is very poorly removed in a liquid medium. A person weighing 70 kg must drive 5 liters of the mixture through himself every minute, and this is in a calm state. Therefore, although our lungs are technically capable of extracting oxygen from liquids, they are too weak. So one can only hope for future research.
water like air
In order to finally proudly announce to the world - "Now a person can breathe underwater!" - scientists sometimes developed amazing devices. So, in 1976, biochemists from America created a miracle device capable of regenerating oxygen from water and providing it to a diver. With sufficient battery capacity, a diver could stay and breathe at depth almost indefinitely.
It all started with the fact that scientists began research based on the fact that hemoglobin delivers air equally well from both the gills and the lungs. They used their own venous blood mixed with polyurethane - it was immersed in water and this liquid absorbed oxygen, which is generously dissolved in water. Further, the blood was replaced with a special material, and as a result, a device was obtained that acted like the usual gills of any fish. The fate of the invention is this: it was acquired by a certain company, having spent 1 million dollars on it, and since then nothing has been heard about the device. And, of course, he did not go on sale.
But this is not the main goal of scientists. Their dream is not a breathing device, they want to teach the person himself to breathe liquid. And attempts to realize this dream have not been abandoned so far. So, one of the research institutes in Russia, for example, conducted tests on liquid breathing on a volunteer with a congenital pathology - the absence of the larynx. And this meant that he simply did not have the reaction of the body to the liquid, in which the smallest drop of water on the bronchi is accompanied by compression of the pharyngeal ring and suffocation. Since he simply did not have this muscle, the experiment was successful. Fluid was poured into his lungs, which he stirred throughout the experiment with the help of abdominal movements, after which it was calmly and safely pumped out. Characteristically, the salt composition of the fluid corresponded to the salt composition of the blood. This can be considered a success, and scientists claim that they will soon find a method of liquid breathing available to people without pathologies.
So myth or reality?
Despite the stubbornness of a person who passionately wants to conquer all possible habitats, nature itself still decides where to live. Alas, no matter how much time is spent on research, no matter how many millions are spent, it is unlikely that a person is destined to breathe under water as well as on land. People and marine life, of course, have a lot in common, but there are still much more differences. An amphibian man would not have endured the conditions of the ocean, and if he had managed to adapt, then the road back to land would have been closed to him. And as with scuba divers, amphibious people would go to the beach in water suits. And therefore, no matter what enthusiasts say, the verdict of scientists is still firm and disappointing - a long life of a person under water is impossible, it is unreasonable to go against mother nature in this regard, and all attempts at liquid breathing are doomed to failure.
But do not despair. Although the bottom of the sea will never become our home, we have all the mechanisms of the body and technical capabilities in order to be frequent guests on it. So is it worth it to be sad? After all, these environments have already been conquered by man to a certain extent, and now the abysses of outer space lie before him.
And for now, we can say with confidence that the depths of the ocean will be an excellent workplace for us. But perseverance can lead to a very thin line of real breathing under water, one has only to work on solving this problem. And what will be the answer to the question of whether to change land civilization to underwater, depends only on the person himself.
Life on our planet originated, apparently, in water - in an environment where oxygen reserves are very scarce. At atmospheric pressure, the oxygen content of air at sea level is 200 milliliters per liter, and less than seven milliliters of oxygen is dissolved in a liter of surface water.
The first inhabitants of our planet, having adapted to the aquatic environment, breathed with gills, the purpose of which is to extract the maximum amount of oxygen from the water.
In the course of evolution, animals mastered the oxygen-rich land atmosphere and began to breathe with their lungs. The functions of the respiratory organs remained the same.
Both in the lungs and in the gills, oxygen from the environment penetrates through thin membranes into the blood vessels, and carbon dioxide is released from the blood into the environment. So, the same processes take place in the gills and in the lungs. This raises the question: would an animal with lungs be able to breathe in an aquatic environment if it contained enough oxygen?
The answer to this question deserves attention for several reasons. First, we could learn why the respiratory organs of terrestrial animals are so different in structure from the corresponding organs of aquatic animals.
In addition, the answer to this question is of purely practical interest. If a specially trained person could breathe in the aquatic environment, then this would facilitate the exploration of the depths of the ocean and travel to distant planets. All this served as the basis for setting up a number of experiments to study the possibility of breathing land mammals with water.
Water breathing problems
The experiments were carried out in the laboratories of the Netherlands and the USA. Breathing water is associated with two main problems. One has already been mentioned: at ordinary atmospheric pressure, too little oxygen is dissolved in water.
The second problem is that water and blood are fluids with very different physiological properties. When “inhaled”, water can damage lung tissue and cause fatal changes in the volume and composition of fluids in the body.
Suppose we have prepared a special isotonic solution, where the composition of salts is the same as in blood plasma. Under high pressure, the solution is saturated with oxygen (its concentration is approximately the same as in air). Will the animal be able to breathe in such a solution?
The first such experiments were carried out at Leiden University. Through an airlock similar to a submarine's lifeboat, the mice were introduced into a chamber filled with a specially prepared solution, which was pressurized with oxygen. Through the transparent walls of the chamber it was possible to observe the behavior of the mice.
In the first few moments, the animals tried to get to the surface, but the wire mesh prevented them. After the first excitement, the mice calmed down and did not seem to suffer much in a similar situation. They made slow, rhythmic breathing movements, apparently inhaling and exhaling fluid. Some of them lived in such conditions for many hours.
The main difficulty of breathing water
After a series of experiments, it became clear that the decisive factor determining the lifespan of mice is not the lack of oxygen (which could be introduced into the solution in any desired amount by simply increasing its partial pressure), but the difficulty of expelling carbon dioxide from the body to the required extent.
The mouse that lived the longest time - 18 hours - was in a solution to which a small amount of an organic buffer, tris(hydroxymethyl)aminomethane, was added. The latter minimizes the adverse effect of carbon dioxide accumulation in animals. Lowering the temperature of the solution to 20°C (about half the normal body temperature of a mouse) also contributed to life extension.
In this case, this was due to a general slowdown in metabolic processes.
Typically, a liter of air exhaled by an animal contains 50 milliliters of carbon dioxide. Other things being equal (temperature, partial pressure of carbon dioxide) in one liter of a saline solution, identical in its salt composition to the blood, only 30 milliliters of this gas dissolves.
This means that in order to release the required amount of carbon dioxide, the animal must inhale twice as much water as air. (But pumping fluid through the bronchial vessels requires 36 times more energy, since the viscosity of water is 36 times higher than the viscosity of air.)
From this it is obvious that even in the absence of turbulent movement of fluid in the lungs, breathing water requires 60 times more energy than breathing air.
Therefore, there is nothing surprising in the fact that the experimental animals gradually weakened, and then - due to exhaustion and accumulation of carbon dioxide in the body - breathing stopped.
Experiment results
Based on the experiments carried out, it was impossible to judge how much oxygen enters the lungs, how saturated it is in the arterial blood, and what is the degree of accumulation of carbon dioxide in the blood of animals. Gradually, we approached a series of more advanced experiments.
They were carried out on dogs in a large chamber equipped with additional equipment. The chamber was filled with air at a pressure of 5 atmospheres. There was also a bath of saline, saturated with oxygen. An experimental animal was immersed in it. Before the experiment, in order to reduce the total body oxygen demand, the dogs were anesthetized and cooled to 32°C.
During the dive, the dog made violent respiratory movements. The trickles of water rising from the surface showed clearly that she was pumping the solution through her lungs. At the end of the experiment, the dog was pulled out of the bath, the water was removed from the lungs, and they were refilled with air. Of the six animals tested, one survived. The dog breathed in the water for 24 minutes.
The results of the experiment can be formulated as follows: under certain conditions, animals that breathe air can breathe water for a limited period of time. The main disadvantage of water breathing is the accumulation of carbon dioxide in the body.
During the experiment, the blood pressure of the surviving dog was somewhat less than normal, but remained constant; pulse and respiration were slow but regular, arterial blood was saturated with oxygen. The content of carbon dioxide in the blood gradually increased.
This meant that the dog's vigorous respiratory activity was insufficient to remove the necessary amounts of carbon dioxide from the body.
A new series of water breathing experiments
At New York State University, I continued to work with Herman Raan, Edward X. Lanfear, and Charles W. Paganelli. In a new series of experiments, instruments were used that made it possible to obtain specific data on the gas exchange that occurs in the lungs of a dog when breathing liquid. As before, the animals breathed a saline solution saturated with oxygen at a pressure of 5 atmospheres.
The gas composition of the inhaled and exhaled fluid was determined at the inlet and outlet of the solution from the lungs of dogs. The oxygen-rich liquid entered the anesthetized dog's body through a rubber tube inserted into the trachea. The flow was regulated by a valve pump.
With each inhalation, the solution flowed down into the lungs under the action of gravity, and during exhalation, the liquid, according to the same principle, entered a special receiver. The amount of oxygen absorbed in the lungs and the amount of carbon dioxide released were determined as the difference between the corresponding values in equal volumes of inhaled and exhaled fluid.
Animals were not cooled. It turned out that under these conditions, the dog extracts about the same amount of oxygen from the water as it usually does from the air. As expected, the animals did not exhale enough carbon dioxide, so the carbon dioxide content in the blood gradually increased.
At the end of the experiment, which lasted up to forty-five minutes, water was removed from the dog's lungs through a special hole in the trachea. The lungs were purged with several portions of air. Additional procedures for "revitalization" were not carried out. Six out of sixteen dogs survived the experiment with no apparent consequences.
Interaction of three elements
The respiration of both fish and mammals is based on a complex interaction of three elements:
1) the needs of the body for gas exchange,
2) the physical properties of the environment and
3) the structure of the respiratory system.
To rise above a purely intuitive assessment of the significance of the structure of organs in the process of adaptation, it is necessary to accurately understand all these interactions. It is obvious that such questions should be asked. How does an oxygen molecule get from the environment into the blood? What is her exact path? Answering these questions is much more difficult than one might think.
When the chest expands, air (or water) enters the lungs of the animal. What happens to the fluid that gets into the border air sacs of the lungs? Let's look at this phenomenon with a simple example.
If a small amount of ink is slowly injected through a needle into a syringe partially filled with water, they first form a thin stream in the center of the vessel. After the "inhalation" stops, the ink gradually spreads throughout the entire volume of water.
If the ink is introduced quickly, so that the flow is turbulent, mixing will, of course, occur much faster. Based on the data obtained, and also taking into account the size of the bronchial tubes, it can be concluded that the inhaled air or water flow enters the air sacs slowly, without turbulence.
Therefore, it can be assumed that when fresh air (or water) is inhaled, oxygen molecules will first concentrate in the center of the air sacs (alveoli). Now they have to overcome significant distances by diffusion before they reach the walls through which they enter the blood.
These distances are many times greater than the thickness of the membranes that separate air from blood in the lungs. If the inhaled medium is air, it does not matter much: oxygen is distributed evenly throughout the alveolus in millionths of a second.
The speed of propagation of gases in water is 6 thousand times less than in air. Therefore, when breathing with water, there is a difference in the partial pressures of oxygen in the central and peripheral regions. Due to the low rate of diffusion of gases, the oxygen pressure in the center of the alveoli becomes higher with each breathing cycle than at the walls. The concentration of carbon dioxide leaving the blood is greater near the walls of the alveoli than in the center.
Gas exchange in the lungs
Such theoretical prerequisites arose on the basis of the study of the gas composition of exhaled fluid during experiments on dogs. Water flowing from the lungs of the dog was collected in a long tube.
It turned out that in the first portion of water, which apparently came from the central part of the alveoli, there was more oxygen than in the last portion, which came from the walls. During the breathing of dogs in the air, no appreciable difference was observed in the compositions of the first and last portions of the exhaled air.
It is interesting to note that the gas exchange that occurs in the lungs of a dog when breathing water is very similar to the process that occurs in a simple drop of water when an exchange is carried out on its surface: oxygen - carbon dioxide. Based on this analogy, a mathematical model of the lungs was built, and a sphere with a diameter of about one millimeter was chosen as a functional unit.
The calculation showed that the lungs comprise about half a million of these spherical gas-exchange cells, in which the transfer of gas is carried out only by diffusion. The calculated number and size of these cells closely match the number and size of certain lung structures called "primary lobules" (lobules).
Apparently, these lobules are the main functional units of the lungs. Similarly, with the involvement of anatomical data, it is possible to construct a mathematical model of the gills of fish, the primary gas exchange units of which will have a correspondingly different shape.
The construction of mathematical models made it possible to draw a clear line between the respiratory organs of mammals and fish. It turns out that the main thing lies in the geometric structure of the respiratory cells. This becomes especially evident when studying the dependence that links the fish's need for gas exchange and the properties of the environment with the shape of the fish's respiratory organs.
The equation expressing this dependence includes such quantities as the availability of oxygen, that is, its concentration, diffusion rate and solubility in the animal's environment.
The volume of air or water inhaled, the number and size of gas exchange cells, the amount of oxygen absorbed by them, and, finally, the pressure of oxygen in the arterial blood. Suppose that fish do not have gills as respiratory organs, but lungs.
Substituting into the equation the real data of gas exchange that occurs during the respiration of fish, we find that a fish with lungs will not be able to live in water, since the calculation shows the complete absence of oxygen in the arterial blood of your fish model.
This means that there was an error in the assumption, namely: the chosen form of the gas exchange cell turned out to be incorrect. Fish live in water thanks to the gills, which consist of flat, thin, densely packed plates. In such a structure - in contrast to the spherical cells of the lungs - there is no problem of diffusion of gases.
An animal with lung-like respiratory organs can only survive in water if its oxygen demand is extremely low. Let's take the sea cucumber as an example.
Gills give fish the ability to live in the water, and these same gills do not allow them to exist out of the water. In air, they collapse under the influence of gravity. Surface tension at the air-water interface causes tightly packed gill plates to stick together.
The total area of the gills available for gas exchange is reduced so much that the fish cannot breathe, despite the abundance of oxygen in the air. The alveoli of the lungs are protected from destruction, firstly, by the chest, and secondly, by a wetting agent released in the lungs, which significantly reduces surface tension.
Respiration of mammals in water
The study of the processes of respiration of mammals in water thus gave new information about the basic principles of respiration in general. On the other hand, there was a real assumption that a person would be able to breathe liquid for a limited time without harmful consequences. This will allow divers to descend to much greater depths of the ocean than now.
The main danger of deep-sea diving is associated with water pressure on the chest and lungs. As a result, the pressure of gases in the lungs rises, and some of the gases enter the bloodstream, which leads to serious consequences. At high pressures, most gases are toxic to the body.
So, nitrogen entering the diver's blood causes intoxication already at a depth of 30 meters and practically puts him out of action at a depth of 90 meters due to the resulting nitrogen anesthesia. (This problem can be solved by using rare gases such as helium, which are not toxic even at very high concentrations.)
In addition, if the diver returns too quickly from depth to the surface, gases dissolved in the blood and tissues are released in the form of bubbles, causing decompression sickness.
This danger can be avoided if the diver does not breathe air, but an oxygen-enriched liquid. The fluid in the lungs will withstand significant external pressure, and its volume will practically not change. Under such conditions, a diver, descending to a depth of several hundred meters, will be able to quickly return to the surface without any consequences.
In order to prove that decompression sickness does not occur when breathing water, the following experiments were carried out in my laboratory. In experiments with a mouse that breathed liquid, a pressure of 30 atmospheres was brought to one atmosphere for three seconds. There were no signs of the disease. This degree of pressure change is equivalent to the effect of lifting from a depth of 910 meters at a speed of 1,100 kilometers per hour.
A person can breathe water
Liquid breathing may be useful to humans during future space travel. When returning from distant planets, for example, from Jupiter, there will be a need for huge accelerations, allowing you to leave the planet's zone of attraction. These accelerations are much greater than what the human body, especially the easily vulnerable lungs, can endure.
But the same loads will become quite acceptable if the lungs are filled with liquid, and the astronaut's body is immersed in a liquid with a density equal to that of blood, just as a fetus is immersed in the amniotic fluid of the mother's womb.
The Italian physiologists Rudolf Margaria, T. Gualterotti and D. Spinelli set up such an experiment in 1958. A steel cylinder containing pregnant rats was thrown from different heights onto a lead support. The purpose of the experiment was to test whether the fetus would survive the harsh deceleration and impact of landing. The deceleration rate was calculated from the depth of indentation of the cylinder into the lead base.
The animals themselves died immediately during the experiment. Autopsies showed significant lung damage. However, the surgically released embryos were alive and developed normally. The fetus, protected by uterine fluid, is able to endure negative accelerations up to 10 thousand g.
After experiments that have shown that land animals can breathe liquid, it is reasonable to assume such a possibility for humans. We now have some direct evidence in favor of this assumption. For example, we are now using a new method for the treatment of certain lung diseases.
The method consists in washing one lung with a saline solution that removes pathological secretions from the alveoli and bronchi. The second lung breathes in gaseous oxygen.
The success of this operation inspired us to set up an experiment for which a courageous deep diver, Francis D. Faleichik, volunteered.
Under anesthesia, a double catheter was inserted into his trachea, each tube of which reached the lungs. At normal body temperature, the air in one lung was replaced with a 0.9% saline solution. The “respiratory cycle” consisted of introducing a saline solution into the lung and then removing it.
The cycle was repeated seven times, with 500 milliliters of solution taken for each "breath". Faleychik, who was fully conscious during the entire procedure, said that he did not notice a significant difference between the light, breathing air, and the light, breathing water. He also did not experience discomfort during the entry and exit of the flow of fluid from the lung.
Of course, this experiment is still very far from trying to carry out the process of breathing with both lungs in water, but it has shown that filling a person's lungs with saline, if the procedure is performed correctly, does not cause serious tissue damage and does not produce unpleasant sensations.
The most difficult problem of breathing water
Probably the most difficult problem to be solved is the release of carbon dioxide from the lungs when breathing water. As we have already said, the viscosity of water is about 36-40 times the viscosity of air. This means that the lungs will pump water at least forty times slower than air.
In other words, a healthy young diver who can breathe 200 liters of air per minute can only breathe 5 liters of water per minute. It is quite obvious that with such breathing, carbon dioxide will not be released in sufficient quantities, even if the person is completely immersed in water.
Can this problem be solved by using a medium in which carbon dioxide dissolves better than in water? In some liquefied synthetic fluorocarbons, carbon dioxide dissolves, for example, three times more than in water, and oxygen - thirty times. Leland S. Clark and Frank Gollan showed that a mouse can live in oxygen-containing liquid carbon fluoride at atmospheric pressure.
Not only does carbon fluoride contain more oxygen than water, but the gas diffusion rate is also four times higher in this medium. However, here, too, the small permeability of the liquid through the lungs remains a stumbling block: fluorocarbons have an even greater viscosity than saline.
Translation from English by N. Poznanskaya.
The Russian Foundation for Advanced Study has begun testing liquid breathing technology for divers on dogs.
Vitaly Davydov, Deputy General Director of the Fund, spoke about this. According to him, full-scale tests are already underway.
In one of his laboratories, work is underway on liquid respiration. While experiments are carried out on dogs. With us, a red dachshund was immersed in a large flask with water, face down. It would seem, why mock the animal, now it will choke. An no. She sat underwater for 15 minutes. The record is 30 minutes. Incredible. It turns out that the dog's lungs were filled with an oxygenated liquid, which made it possible for her to breathe underwater. When they pulled her out, she was a little lethargic - they say, due to hypothermia (and I think who likes to stick around under water in a jar in front of everyone), but after a few minutes she became quite herself. Soon the experiments will be carried out on people, - says the journalist of Rossiyskaya Gazeta, Igor Chernyak, who became an eyewitness to unusual tests.
All this was similar to the fantastic plot of the famous film "The Abyss", where a person could descend to a great depth in a spacesuit, the helmet of which was filled with liquid. The submariner breathed with it. Now it is no longer fantasy.
The technology of liquid breathing involves filling the lungs with a special liquid saturated with oxygen, which penetrates into the blood. The Advanced Research Foundation approved the implementation of a unique project, the work is being carried out by the Research Institute of Occupational Medicine. It is planned to create a special suit that will be useful not only for submariners, but also for pilots and astronauts.
As Vitaly Davydov told a TASS correspondent, a special capsule was created for dogs, which was immersed in a high-pressure hydrochamber. At the moment, dogs can breathe without health consequences for more than half an hour at a depth of up to 500 meters. "All test dogs survived and feel good after prolonged liquid breathing," the deputy head of the FPI assured.
Few people know that experiments on liquid breathing have already been carried out on people in our country. Gave amazing results. Aquanauts breathed liquid at a depth of half a kilometer or more. That's just the people about their heroes did not know.
In the 1980s, the USSR developed and began to implement a serious program to save people at depth.
Special rescue submarines were designed and even commissioned. The possibilities of human adaptation to depths of hundreds of meters were studied. Moreover, the aquanaut was supposed to be at such a depth not in a heavy diving suit, but in a light insulated wetsuit with scuba gear behind his back, his movements were not constrained by anything.
Since the human body consists almost entirely of water, the terrible pressure at depth is not dangerous for him in itself. The body should simply be prepared for it by increasing the pressure in the pressure chamber to the required value. The main problem is elsewhere. How to breathe at a pressure of tens of atmospheres? Clean air becomes poison for the body. It must be diluted in specially prepared gas mixtures, usually nitrogen-helium-oxygen.
Their recipe - the proportions of various gases - is the biggest secret in all countries where similar studies are underway. But at very great depths, helium mixtures do not save. The lungs must be filled with fluid so that they do not burst. What is a liquid that, once in the lungs, does not lead to suffocation, but transfers oxygen through the alveoli to the body - a secret from secrets.
That is why all work with aquanauts in the USSR, and then in Russia, was carried out under the heading "top secret".
Nevertheless, there is quite reliable information that in the late 1980s there was a deep-water aquatic station in the Black Sea, in which test submariners lived and worked. They went out to sea, dressed only in wetsuits, with scuba gear on their backs, and worked at depths of 300 to 500 meters. A special gas mixture was fed into their lungs under pressure.
It was assumed that if the submarine was in distress and sank to the bottom, then a rescue submarine would be sent to it. Aquanauts will be prepared in advance for work at the appropriate depth.
The hardest thing is to be able to withstand the filling of the lungs with liquid and just not die of fear.
And when the rescue submarine approaches the disaster site, divers in light equipment will go out into the ocean, inspect the emergency boat and help evacuate the crew with the help of special deep-sea submersibles.
It was not possible to complete those works due to the collapse of the USSR. However, those who worked at depth still managed to be awarded the stars of the Heroes of the Soviet Union.
Probably, even more interesting studies were continued in our time near St. Petersburg on the basis of one of the Naval Research Institutes.
There, too, experiments were conducted on gas mixtures for deep-sea research. But, most importantly, perhaps for the first time in the world, people there learned to breathe liquid.
In their uniqueness, those jobs were much more complex than, say, preparing astronauts for flights to the moon. The testers were subjected to enormous physical and psychological stress.
First, the body of aquanauts in an air pressure chamber was adapted to a depth of several hundred meters. Then they moved into a chamber filled with liquid, where they continued to dive to depths, they say, almost a kilometer.
The hardest part, according to those who did have a chance to talk with aquanauts, according to them, was to withstand the filling of the lungs with liquid and simply not die of fear. This is not about cowardice. Fear of choking is a natural reaction of the body. Anything could happen. Spasm of the lungs or cerebral vessels, even a heart attack.
When a person understood that the liquid in the lungs does not bring death, but bestows life at a great depth, quite special, truly fantastic sensations arose. But only those who have experienced such an immersion know about them.
Alas, the work, amazing in its significance, was stopped for an elementary reason - due to lack of finances. Heroes-aquanauts were given the title of Heroes of Russia and retired. The names of the submariners are classified to this day.
Although they should have been honored as the first astronauts, because they paved the way to the deep hydrospace of the Earth.
Now experiments on liquid breathing have been resumed, they are being carried out on dogs, mainly dachshunds. They also experience stress.
But researchers pity them. As a rule, after underwater experiments, they take them to live in their homes, where they are fed with yummy, surrounded by affection and care.
