If the pressure is too low, a person may lose consciousness, stroke, or cardiogenic shock is possible. A sharp increase in blood pressure in a hypertensive patient is fraught with a heart attack or stroke. Blood pressure over 180 mm Hg is dangerous.
A significant increase or decrease in blood pressure poses a serious threat to human life and can cause the development of pathologies of the heart, circulatory system, and kidneys. The scientists concluded that the prognosis for patient survival worsens both at too high and at critically low blood pressure values. Lethal pressure for a person with hypertension is above 180/110 mmHg. Art., and with hypotension – below 45 mm Hg. Art.
People suffering from hypertension notice a progressive increase in blood pressure levels. With pathological hypertension, narrowing and spasm of blood vessels occurs, the disease develops after suffering a psycho-emotional shock, with atherosclerosis, coronary artery disease.
Another cause of high blood pressure is excessive blood viscosity: the body tries to speed up blood flow, and therefore the pressure rises. The number of contractions of the heart muscle increases, and vascular tone increases. If the blood viscosity is excessive, blood clots form and blood vessels become blocked; the pathology is complicated by infarction and tissue necrosis, to which O₂ and essential nutrients cease to flow.
An increase in the total volume of circulating blood in the body also increases blood pressure. This condition is observed with excessive consumption of table salt, metabolic disorders, and diabetes mellitus.
Hypertension is classified into 3 stages:
I. Blood pressure readings up to 140–150/90–100 mm Hg are recorded. Art.
II. Marks on the tonometer reach 150–170/95–100 mmHg. Art.
III. Blood pressure exceeds 180/110 mm Hg. Art.
At the initial stage, short attacks occur, internal organs are not affected. In moderate forms of hypertension, blood pressure rises more often and medications are required to reduce it.
The third stage is characterized by high blood pressure levels and disruption of target organs. Dystrophic changes occur in the myocardium, the walls of blood vessels thicken and lose elasticity, blood supply to peripheral tissues deteriorates, and vision problems arise. Against the background of a critical increase in pressure, a hypertensive crisis, hemorrhagic stroke, heart attack, heart and kidney failure develop. Without assistance, death occurs.
Low pressure danger
Hypotension is accompanied by insufficient blood supply to the brain and heart, tissues experience oxygen starvation. With prolonged hypotension, a heart attack develops, death or severe disability occurs.
There are physiological and pathological decreases in blood pressure. Normally, blood pressure may drop after intense sports training, overwork, or when climbing mountains. Pathological hypotension occurs against the background of stress, endocrine diseases, dysfunction of the kidneys, heart and vascular system.
Drugs that lower blood pressure can lead to a sharp drop in blood pressure if the dosage is incorrect.
Arterial hypotension is diagnosed when the tonometer readings drop to 80/60 mmHg. Art. and less. The pathology occurs in acute or chronic form. With the rapid progression of the disease, the symptoms of hypotension appear suddenly and increase rapidly. A decrease in blood pressure occurs over a short period of time, and the development of cardiogenic, orthostatic shock, and loss of consciousness is possible. Without timely action, a person dies.
Impaired peripheral circulation leads to a lack of oxygen; the brain and internal organs suffer from hypoxia. A person’s health deteriorates, dizziness, weakness appear, fog appears before the eyes, noise in the ears, and fainting occurs.
You can die from a stroke with critical blood pressure levels of 40–45 mm Hg. Art.
With chronic low blood pressure, dangerous complications develop less frequently. In some cases, blood pressure readings of 85–90/60 are also recorded in healthy people who do not suffer from any diseases, so blood pressure readings are individual for each person.
How to normalize blood pressure
In case of hypotension, it is important to increase and stabilize blood pressure. This requires the use of hormonal drugs that increase vascular tone: Adrenaline, Prednisolone. Stimulates the central nervous system and brain chemoreceptors Cordiamine. The drug speeds up breathing movements, inhalation becomes deeper, the body begins to receive more oxygen, blood pressure normalizes, and health improves.
To increase pressure when the volume of circulating blood decreases, infusions of colloidal and saline solutions are made: Sodium chloride, Reopoliglucin. If the cause of low blood pressure is heart failure, intravenous administration of glycosides is prescribed: Corglicon, Digoxin.
Patients often ask the question: at what pressure is it necessary to call an ambulance? Emergency treatment is required for fainting, increased blood pressure more than 180/110, or a decrease in systolic value less than 45 mm Hg. Art. Before the doctor arrives, you can take the medicine that the patient drinks constantly, put a Nitroglycerin tablet under the tongue.
In severe cases of hypertension, crisis, blood pressure is lowered with the help of diuretics, β-blockers, ACE inhibitors, neurotransmitters, alpha-2-adrenergic receptor agonists of the brain, Enalaprilat. If systolic readings reach 200 mm Hg. Art., to lower blood pressure, the patient is prescribed Clonidine, Nifedipine, Prazosin. The drugs are selected by the attending physician individually for each patient, taking into account what disease caused the pathology.
Treatment with folk remedies
At home you can use medicinal herbs. Immortelle is used to prepare a decoction for hypotension. The medicine is prepared from 2 tablespoons of a dry plant, pour 0.5 liters of boiling water into a container and leave for 2 hours. After this, strain the composition and drink half a glass twice a day until the pressure normalizes.
You can lower blood pressure during a hypertensive crisis and prevent the symptoms of an advancing coma with the help of hawthorn, calendula, rowan fruits, rose hips, motherwort, peppermint, yarrow, and knotweed. During treatment, you should take into account that there are contraindications for use.
Home therapy with folk remedies should be carried out in combination with medication and only after consulting a doctor.
In the event of a sharp change in blood pressure and untimely provision of assistance to the patient, death occurs from a heart attack, stroke, heart failure, renal failure, intravascular coagulation, and possible swelling of the brain and lungs. The prognosis worsens with concomitant diseases; five-year survival is observed in patients who received qualified assistance with a sharp decrease or increase in blood pressure.
The human body is very delicate. Without additional protection, it can only function in a narrow temperature range and at a certain pressure. It must constantly receive water and nutrients. And it will not survive a fall from a height greater than a few meters. How much can the human body withstand? When is our body at risk of death? Fullpicture presents to your attention a unique overview of the facts about the limits of survival of the human body.
8 PHOTOS
The material was prepared with the support of the Docplanner service, thanks to which you will quickly find the best medical institutions in St. Petersburg - for example, the Dzhanelidze Emergency Medical Center.
1. Body temperature.
Survival limits: body temperature can vary from +20° C to +41° C.
Conclusions: usually our temperature ranges from 35.8 to 37.3 ° C. This temperature regime of the body ensures the uninterrupted functioning of all organs. At temperatures above 41°C, significant loss of body fluids, dehydration and organ damage occurs. At temperatures below 20° C, blood flow stops.
The human body temperature is different from the ambient temperature. A person can live in an environment with temperatures ranging from -40 to +60° C. Interestingly, a decrease in temperature is just as dangerous as its increase. At a temperature of 35 C, our motor functions begin to deteriorate, at 33 ° C we begin to lose orientation, and at a temperature of 30 ° C we lose consciousness. A body temperature of 20° C is the limit below which the heart stops beating and a person dies. However, medicine knows of a case where it was possible to save a man whose body temperature was only 13° C. (Photo: David Martín/flickr.com).
2. Heart performance. Survival limits: from 40 to 226 beats per minute.
Conclusions: A low heart rate leads to low blood pressure and loss of consciousness, too high - to a heart attack and death.
The heart must constantly pump blood and distribute it throughout the body. If the heart stops working, brain death occurs. The pulse is a pressure wave induced by the release of blood from the left ventricle into the aorta, from where it is distributed by arteries throughout the body.
Interesting: the “life” of the heart in most mammals averages 1,000,000,000 beats, while a healthy human heart performs three times as many beats over its entire life. A healthy adult heart beats 100,000 times a day. Professional athletes often have a resting heart rate of only 40 beats per minute. The length of all the blood vessels in the human body, if connected, is 100,000 km, which is two and a half times longer than the length of the Earth's equator.
Did you know that the total power of the human heart over 80 years of human life is so great that it could pull a steam locomotive up the highest mountain in Europe - Mont Blanc (4810 m above sea level)? (Photo: Jo Christian Oterhals/flickr.com).
3. Brain overload with information. Survival limits: each person is individual.
Conclusions: Information overload causes the human brain to become depressed and stop functioning properly. The person is confused, begins to delirium, sometimes loses consciousness, and after the symptoms disappear, he does not remember anything. Long-term brain overload can lead to mental illness.
On average, the human brain can store as much information as 20,000 average dictionaries. However, even such an efficient organ can “overheat” due to excess information.
Interesting: the shock that occurs as a result of extreme irritation of the nervous system can lead to a state of numbness (stupor), in which case the person loses control of himself: he can suddenly go out, become aggressive, talk nonsense and behave unpredictably.
Did you know that the total length of nerve fibers in the brain ranges from 150,000 to 180,000 km? (Photo: Zombola Photography/flickr.com).
4. Noise level. Survival limits: 190 decibels.
Conclusions: at a noise level of 160 decibels, people's eardrums begin to burst. More intense sounds can damage other organs, particularly the lungs. The pressure wave ruptures the lungs, causing air to enter the bloodstream. This in turn leads to blockage of the blood vessels (embolism), which causes shock, myocardial infarction, and ultimately death.
Typically the range of noise we experience ranges from 20 decibels (a whisper) to 120 decibels (a plane taking off). Anything above this limit becomes painful for us. Interesting: Being in a noisy environment is harmful to a person, reduces his efficiency and distracts him. A person is unable to get used to loud sounds.
Did you know that loud or unpleasant sounds are still used, unfortunately, during the interrogation of prisoners of war, as well as when training secret service soldiers? (Photo: Leanne Boulton/flickr.com).
5. The amount of blood in the body. Survival limits: loss of 3 liters of blood, that is, 40-50 percent of the total amount in the body.
Conclusions: A lack of blood causes the heart to slow down because it has nothing to pump. The pressure drops so much that blood can no longer fill the chambers of the heart, causing it to stop. The brain does not receive oxygen, stops working and dies.
The main task of blood is to distribute oxygen throughout the body, that is, saturate all organs with oxygen, including the brain. In addition, the blood removes carbon dioxide from tissues and distributes nutrients throughout the body.
Interesting: the human body contains 4-6 liters of blood (which makes up 8% of body weight). Losing 0.5 liters of blood in adults is not dangerous, but when the body lacks 2 liters of blood, there is a great risk to life, in such cases medical attention is necessary.
Did you know that other mammals and birds have the same ratio of blood to body weight - 8%? And the record amount of blood lost in a person who still survived was 4.5 liters? (Photo: Tomitheos/flickr.com).
6. Height and depth. Survival limits: from -18 to 4500 m above sea level.
Conclusions: if a person without training, who does not know the rules, and without special equipment dives to a depth of more than 18 meters, he is at risk of ruptured eardrums, damage to the lungs and nose, too high pressure in other organs, loss of consciousness and death from drowning. Whereas at an altitude of more than 4500 meters above sea level, a lack of oxygen in the inhaled air for 6-12 hours can lead to swelling of the lungs and brain. If a person cannot descend to a lower altitude, he will die.
Interesting: an untrained human body without special equipment can live in a relatively small altitude range. Only trained people (divers and climbers) can dive to a depth of more than 18 meters and climb to the tops of mountains, and even they use special equipment for this - diving cylinders and climbing equipment.
Did you know that the record for diving with one breath belongs to the Italian Umberto Pelizzari - he dived to a depth of 150 m. During the dive, he experienced enormous pressure: 13 kilograms per square centimeter of the body, that is, about 250 tons for the entire body. (Photo: B℮n/flickr.com).
7. Lack of water. Survival limits: 7-10 days.
Conclusions: lack of water for a long time (7-10 days) leads to the fact that the blood becomes so thick that it cannot move through the vessels, and the heart is not able to distribute it throughout the body.
Two-thirds of the human body (weight) consists of water, which is necessary for the proper functioning of the body. The kidneys need water to remove toxins from the body, the lungs need water to moisten the air we exhale. Water is also involved in the processes occurring in the cells of our body.
Interesting: when the body lacks about 5 liters of water, a person begins to feel dizzy or faint. With a lack of water of 10 liters, severe convulsions begin, with a 15-liter shortage of water, a person dies.
Did you know that in the process of breathing we consume about 400 ml of water daily? Not only a lack of water, but its excess can kill us. Such a case occurred with one woman from California (USA), who drank 7.5 liters of water in a short period of time during a competition, as a result of which she lost consciousness and died a few hours later. (Photo: Shutterstock).
8. Hunger. Survival limits: 60 days.
Conclusions: lack of nutrients affects the functioning of the entire body. A fasting person's heart rate slows, blood cholesterol levels rise, heart failure and irreversible damage to the liver and kidneys occur. A person exhausted by hunger also has hallucinations, he becomes lethargic and very weak.
A person eats food to provide himself with energy for the functioning of the whole body. A healthy, well-nourished person who has access to enough water and is in a friendly environment can survive about 60 days without food.
Interesting: the feeling of hunger usually appears a few hours after the last meal. During the first three days without food, the human body uses energy from the last food eaten. Then the liver begins to break down and consume fat from the body. After three weeks, the body begins to burn energy from muscles and internal organs.
Did you know that the American Amerykanin Charles R. McNabb, who went on hunger strike in prison for 123 days in 2004, remained the longest without food and survived? He only drank water and sometimes a cup of coffee.
Did you know that every day about 25,000 people die from hunger in the world? (Photo: Rubén Chase/flickr.com).
Blood pressure reflects the internal state of a person. Its indicators can change significantly under the influence of certain extraneous factors. High blood pressure can pose a serious risk to human health. It can increase in the presence of various diseases. That is why if your blood pressure regularly increases, you should immediately consult a doctor. If this recommendation is not followed, the condition may worsen significantly and result in serious deviations. Treatment should also be supervised by a medical professional.
High blood pressure is a symptom of many diseases
Highest blood pressure and its dangers
Not everyone thought about what the highest blood pressure was recorded in a person. To begin with, we note that blood pressure is the force with which blood moves through the vessels. Pressure is systolic and diastolic. The highest rates that have been recorded in the world are 310/220 mmHg. Art. Not every person can withstand this level of blood pressure.
If the norm is exceeded, appropriate measures must be taken immediately. It is necessary to provide first aid, which will help normalize the indicators.
Increased blood pressure levels can pose a huge danger to human health and life. If there is a risk of its increase, you must undergo a course of treatment prescribed by your doctor. Experts recommend measuring indicators throughout the day. This needs to be done at different times of the day. Thanks to this, you can get the most objective picture of the condition.
Measure your blood pressure at least 2 times a day: morning and evening
Due to a regular increase in blood pressure, a stagnation process may begin in the vessels. In the future, this can lead to their rupture. Blood pressure levels usually increase due to the following abnormalities:
- stressful situations;
- excessive physical activity;
- change in climate or weather conditions;
- overvoltage;
- wrong lifestyle;
- lack of sleep;
- emotional overstrain.
These are the main factors that lead to an increase in blood pressure levels. In this case, a person experiences a lot of unpleasant symptoms, and doing normal things becomes impossible.
An excessive increase in blood pressure can lead not only to complications, but also to death. If there is a sharp jump in indicators, it is advisable to call an ambulance.
If your blood pressure suddenly rises above 150, call an ambulance
A prolonged increase in pressure can lead to irreversible changes in the body. First of all, the so-called target organs suffer. These include:
- organs of vision;
- heart;
- excretory organs;
- brain.
Negative symptoms can become chronic. In some cases, the patient may experience a hypertensive crisis. This condition is characterized by a spontaneous increase in blood pressure. It can result in myocardial infarction, stroke or heart failure.
To prevent the condition from worsening, the patient must undergo regular medical therapy. It should be carried out using the medications prescribed by the specialist.
Pressure norms and systolic indicators
Experts distinguish between systolic and diastolic blood pressure. Each of them has its own characteristics and norms. Systolic pressure is the indicator that is observed during peak compression of the heart. It is also called the top one. It demonstrates the force with which biological fluid presses on the walls of the arteries at the moment the heart contracts.
Upper pressure is systolic, lower pressure is diastolic
120/80 is the blood pressure that is considered normal. If it regularly increases, a person may be diagnosed with hypertension. In this case, there is a need for special treatment. Experts say that high or low blood pressure is not always a deviation. Some people's blood pressure may be different. It will be considered normal if the person does not have any negative symptoms and feels great.
With a pathological increase in indicators, the following symptoms may be observed:
- difficulty breathing;
- sleep disturbance;
- refusal to eat;
- change in skin color;
- paroxysmal pain in the head;
- loss of sensation;
- disturbances in the functioning of the organs of vision and hearing;
- severe dizziness;
- loss of consciousness.
With a pathological deviation from the norm, it is difficult for a person to perform even the easiest and most everyday tasks. He has a marked deterioration in his condition. It is customary for specialists to diagnose a pathological increase in blood pressure when its levels exceed 140/90.
Ideal pressure 120/80
With a slight deviation in most cases, a person does not have cardiovascular disorders, and the increase in pressure is due to extraneous factors. After a short period of time, it is restored without outside help, and the patient does not need special treatment. However, first of all, doctors pay attention to the individual characteristics of the patient. This is because for some, normal blood pressure is less than 120/80.
For any deviations, especially if they occur on a regular basis, it is advisable to visit a doctor. This is necessary in order to make sure that the indicators present are normal and do not indicate the presence of any pathologies of the cardiovascular system.
Typically, with a pathological deviation from the norm, both upper and lower blood pressure increases. Only in some cases only one indicator increases.
What is the maximum blood pressure that can be withstood?
Any deviation of blood pressure from the norm can result in significant complications. It is important to know how much pressure a person can withstand. It is impossible to answer this question accurately. All people have certain characteristics of the body. They react differently to blood pressure deviations. Experts say that an increase of 25-30 units can already be regarded as a potential danger.
Hypertension can be diagnosed in a person whose blood pressure level exceeds 140/95. When blood pressure increases by 20 units, the patient experiences a whole range of unpleasant symptoms. The greatest danger is posed by a spontaneous and rapid increase in blood pressure, but small changes are usually short-lived.
Headache and high blood pressure are the main symptoms of hypertension
Experts note that it is rare to encounter patients whose upper blood pressure levels have reached 300 units. Not every person can withstand this level. Usually, at such rates, death occurs.
Experts say that the maximum blood pressure that a person can withstand is 260/140. At higher rates, many patients die or have irreversible consequences. This condition may lead to:
- heart failure;
- ischemic stroke;
- apoplexy.
To prevent irreversible consequences, you need to call a doctor as soon as possible when the first symptoms of increased blood pressure appear.
Treatment and prevention
Blood pressure levels depend on many different factors. Experts recommend taking preventive measures to prevent its increase. To do this you need:
- take walks in the fresh air every day;
- give preference to moderate physical activity;
- completely change your diet and give preference to healthy foods;
- completely give up bad habits;
- avoid stressful situations;
- get as much rest as possible;
- get rid of excess weight;
- observe the drinking regime.
Follow simple rules to prevent hypertension
Nutrition has a significant impact on blood pressure and the cardiovascular system in general. Often, it is due to an incorrect diet that deviations occur. Experts recommend avoiding the use of:
- excessive amounts of salt (you can consume no more than 3 grams per day);
- instant food products;
- drinks with gas (it is better to give preference to homemade juices and fruit drinks);
- fatty meats and some dairy products;
- alcohol-containing drinks, since almost all alcohol leads to a rapid increase in blood pressure;
- seasonings, as they often contain excessive amounts of salt and harmful additives;
- mayonnaise - such a sauce causes an increase in cholesterol in the blood (this contributes to the formation of cholesterol plaques, which always lead to an increase in blood pressure).
Lack of water can cause high blood pressure
To treat hypertension, it is customary for a patient to be prescribed several medications, since combination therapy is most effective.
In some cases, treatment must be carried out continuously, especially if the patient has an advanced stage of arterial hypertension.
Most often, patients are prescribed the following medications:
- Arifon;
- Coronal;
- Uregit;
- Nebilet.
All medications can only be prescribed by a doctor. The doctor selects the drug based on individual characteristics. Self-medication is prohibited, since a drug that has a positive effect on one patient may harm another patient. In some cases, side effects may occur after taking the medication. In this case, you will need to consult your doctor.
You can learn more about the causes of increased blood pressure and the appearance of hypertension from the video:
Health
Hypertension is a condition in which the pressure inside a person’s arteries is systematically characterized by high levels. When a person's blood pressure rises significantly, his heart is forced to work harder, expanding more, to maintain adequate blood supply to all organs of the body. The long-term phenomenon of high blood pressure can lead to disturbances in the functioning of the heart, resulting in a condition called hypertensive cardiopathy. The increase in blood pressure itself is recorded by measuring two indicators: systolic and diastolic pressure.
Systolic pressure is an indicator recorded at the moment of contraction of the heart muscle (actually, “systole” is “compression” or “contraction” from Greek), while the diastolic indicator characterizes the pressure at the moment the heart relaxes between its contractions. In other words, the systolic reading is always greater than the diastolic reading. This is why blood pressure is expressed in two numbers: for example, normal blood pressure, which in most cases is 120/80 millimeters of mercury, consists of two parts, in which the upper number is systolic pressure and the lower number is diastolic pressure. However, 120/80 Not all people have normal blood pressure. For example, in young girls, the pressure is often 90/60 millimeters of mercury, which is also the norm for them.
When measuring blood pressure, it is very important to take into account this indicator: like pulse blood pressure, which is the difference between systolic and diastolic readings. In older people, pulse blood pressure may typically rise as diastolic pressure decreases as large blood vessels lose their elasticity with age. This condition is called isolated systolic hypertension, and it threatens a number of complications. And even if only the systolic indicator significantly exceeds the norm, and diastolic pressure is at normal levels(or even below it), we are still talking about the presence of a certain type of hypertension, which, of course, needs to be brought under control.
Researchers believe that the average normal blood pressure during the day should not exceed 130/80 millimeters of mercury. The diagnosis of hypertension is then made when blood pressure systematically exceeds 140 millimeters of mercury (systolic) and 90 millimeters of mercury (diastolic pressure). Thus, we have to consider normal pressure that is between 130/80 and 140/90 millimeters of mercury. It is also known that a condition such as hypertension can worsen significantly within literally two to five years, unless the patient changes his lifestyle in time. People are most at risk for rapid progression of the condition suffering, for example, from diabetes. However, even in their case, blood pressure can be restored with medication. Although the goal for a healthy person is a blood pressure value that does not exceed 140/90, people at risk should aim for values that do not exceed 120/80 millimeters of mercury. Otherwise they are at greater risk of internal organ damage than people who do not suffer from any underlying diseases.
If we talk about the value of blood pressure, which already poses a serious danger to humans and requires urgent medical attention, then this value is more than 180/110 millimeters of mercury. If the pressure exceeds 200/120, this condition threatens with very immediate consequences that threaten the patient’s life. This phenomenon is called arterial malignant hypertension. The diagnosis of hypertension is made at much lower levels. Experts believe that such a phenomenon as hypertension occurs at an arbitrarily stable level of pressure, above which subsequent treatment is characterized by more advantages for the human body than disadvantages. This condition is diagnosed when the blood pressure is consistently above the highest normal level (139/89 millimeters of mercury), as confirmed by several random blood pressure measurements. If we talk about people at risk for hypertension, that is, those who are at greatest risk of developing heart disease (diabetics), or people already suffering from various heart-related pathologies, then treatment should be prescribed to them already at a pressure that exceeds 130/80 millimeters of mercury.
However, if we talk about pressure values, on the basis of which relevant specialists usually make a diagnosis, then it should be mentioned that these values do not always indicate hypertension. This happens, for example, with so-called “white coat” hypertension, when a person’s blood pressure steadily increases in a hospital setting at the time it is measured. Experts sometimes explain this phenomenon by the emotional stress that some people experience at that moment, when medical workers take their blood pressure. It is noteworthy that pressure measurements in such people at home do not indicate serious deviations from the norm (or even record absolutely normal values). Unlike regular hypertension, white coat hypertension does not pose a particular risk to humans. Be that as it may, I can recommend to such people Monitor your blood pressure regularly(at least at home), since “white coat” hypertension can turn into regular hypertension over time.
We live on a planet of water, but we know the Earth's oceans less well than some cosmic bodies. More than half of the surface of Mars has been mapped with a resolution of about 20 m - and only 10-15% of the ocean floor has been studied with a resolution of at least 100 m. 12 people have been on the Moon, three have been to the bottom of the Mariana Trench, and all of them did not dare to stick their nose out of the heavy-duty bathyscaphes.
Let's dive in
The main difficulty in the development of the World Ocean is pressure: for every 10 m of depth it increases by another atmosphere. When the count reaches thousands of meters and hundreds of atmospheres, everything changes. Liquids flow differently, gases behave unusually... Devices capable of withstanding these conditions remain piecemeal products, and even the most modern submarines are not designed for such pressure. The maximum diving depth of the latest Project 955 Borei nuclear submarines is only 480 m.
Divers descending hundreds of meters are respectfully called aquanauts, comparing them with space explorers. But the abyss of the seas is in its own way more dangerous than the vacuum of space. If something happens, the crew working on the ISS will be able to transfer to the docked ship and in a few hours will be on the surface of the Earth. This route is closed to divers: it may take weeks to evacuate from the depths. And this period cannot be shortened under any circumstances.
However, there is an alternative route to depth. Instead of creating ever more durable hulls, you can send there... living divers. The record of pressure endured by testers in the laboratory is almost double the capabilities of submarines. There is nothing incredible here: the cells of all living organisms are filled with the same water, which freely transfers pressure in all directions.
Cells do not resist the water column, like the solid hulls of submarines, they compensate for external pressure with internal ones. It is not for nothing that the inhabitants of “black smokers”, including roundworms and shrimp, feel great at many kilometers deep in the ocean floor. Some types of bacteria can withstand even thousands of atmospheres quite well. Man is no exception here - the only difference is that he needs air.
Beneath the surface
Oxygen Breathing tubes made of reeds were known to the Mohicans of Fenimore Cooper. Today, hollow plant stems have been replaced by plastic tubes, “anatomically shaped” and with comfortable mouthpieces. However, this did not make them more effective: the laws of physics and biology interfere.
Already at a meter depth, the pressure on the chest rises to 1.1 atm - 0.1 atm of water column is added to the air itself. Breathing here requires a noticeable effort of the intercostal muscles, and only trained athletes can cope with this. At the same time, even their strength will not last long and at a maximum of 4-5 m depth, and beginners have difficulty breathing even at half a meter. In addition, the longer the tube, the more air it contains. The “working” tidal volume of the lungs is on average 500 ml, and after each exhalation, part of the exhaust air remains in the tube. Each breath brings less oxygen and more carbon dioxide.
Forced ventilation is required to deliver fresh air. By pumping gas under increased pressure, you can ease the work of the chest muscles. This approach has been used for more than a century. Hand pumps have been known to divers since the 17th century, and in the middle of the 19th century, English builders who erected underwater foundations for bridge supports already worked for a long time in an atmosphere of compressed air. For the work, thick-walled, open-bottom underwater chambers were used, in which high pressure was maintained. That is, caissons.
Deeper than 10 m
Nitrogen No problems arose during work in the caissons themselves. But upon returning to the surface, construction workers often developed symptoms that French physiologists Paul and Vattel described in 1854 as On ne paie qu'en sortant - "payback at the exit." It could be severe itching of the skin or dizziness, pain in the joints and muscles. In the most severe cases, paralysis developed, loss of consciousness occurred, and then death.
To go to the depths without any difficulties associated with extreme pressure, you can use heavy-duty spacesuits. These are extremely complex systems that can withstand immersion of hundreds of meters and maintain a comfortable pressure of 1 atm inside. True, they are very expensive: for example, the price of a recently introduced spacesuit from the Canadian company Nuytco Research Ltd. EXOSUIT is about a million dollars.
The problem is that the amount of gas dissolved in a liquid directly depends on the pressure above it. This also applies to air, which contains about 21% oxygen and 78% nitrogen (other gases - carbon dioxide, neon, helium, methane, hydrogen, etc. - can be neglected: their content does not exceed 1%). If oxygen is quickly absorbed, then nitrogen simply saturates the blood and other tissues: with an increase in pressure by 1 atm, about 1 additional liter of nitrogen dissolves in the body.
With a rapid decrease in pressure, excess gas begins to be released rapidly, sometimes foaming, like an opened bottle of champagne. The resulting bubbles can physically deform tissues, block blood vessels and deprive them of blood supply, leading to a wide variety of and often severe symptoms. Fortunately, physiologists figured out this mechanism quite quickly, and already in the 1890s, decompression sickness could be prevented by using a gradual and careful decrease in pressure to normal - so that nitrogen leaves the body gradually, and blood and other fluids do not “boil” .
At the beginning of the twentieth century, English researcher John Haldane compiled detailed tables with recommendations on the optimal modes of descent and ascent, compression and decompression. Through experiments with animals and then with people - including himself and his loved ones - Haldane found that the maximum safe depth without requiring decompression was about 10 m, and even less for a long dive. Returning from the depths should be done gradually and slowly to give the nitrogen time to be released, but it is better to descend rather quickly, reducing the time for excess gas to enter the body tissues. New limits of depth were revealed to people.
Deeper than 40 m
Helium The fight against depth is like an arms race. Having found a way to overcome the next obstacle, people took a few more steps - and met a new obstacle. So, after decompression sickness, a scourge appeared, which divers almost lovingly call “nitrogen squirrel”. The fact is that under hyperbaric conditions this inert gas begins to act no worse than strong alcohol. In the 1940s, the intoxicating effect of nitrogen was studied by another John Haldane, the son of “the same one.” His father’s dangerous experiments did not bother him at all, and he continued harsh experiments on himself and his colleagues. “One of our subjects suffered a lung rupture,” the scientist wrote in the journal, “but he is now recovering.”
Despite all the research, the mechanism of nitrogen intoxication has not been established in detail - however, the same can be said about the effect of ordinary alcohol. Both disrupt normal signal transmission at the synapses of nerve cells, and perhaps even change the permeability of cell membranes, turning ion exchange processes on the surfaces of neurons into complete chaos. Outwardly, both manifest themselves in similar ways. A diver who “caught a nitrogen squirrel” loses control of himself. He may panic and cut the hoses, or, conversely, get carried away by telling jokes to a school of cheerful sharks.
Other inert gases also have a narcotic effect, and the heavier their molecules, the less pressure is required for this effect to manifest itself. For example, xenon is anesthetic under normal conditions, but lighter argon is anesthetic only under several atmospheres. However, these manifestations are deeply individual, and some people, when diving, feel nitrogen intoxication much earlier than others.
You can get rid of the anesthetic effect of nitrogen by reducing its intake into the body. This is how nitrox breathing mixtures work, containing an increased (sometimes up to 36%) proportion of oxygen and, accordingly, a reduced amount of nitrogen. It would be even more tempting to switch to pure oxygen. After all, this would make it possible to quadruple the volume of breathing cylinders or quadruple the time of working with them. However, oxygen is an active element, and with prolonged inhalation it is toxic, especially under pressure.
Pure oxygen causes intoxication and euphoria, and leads to membrane damage in the cells of the respiratory tract. At the same time, the lack of free (reduced) hemoglobin makes it difficult to remove carbon dioxide, leads to hypercapnia and metabolic acidosis, triggering physiological reactions of hypoxia. A person suffocates, despite the fact that his body has enough oxygen. As the same Haldane Jr. established, even at a pressure of 7 atm, you can breathe pure oxygen for no longer than a few minutes, after which breathing disorders, convulsions begin - everything that in diving slang is called the short word “blackout”.
Liquid breathing
The still semi-fantastic approach to conquering depth is to use substances that can take over the delivery of gases instead of air - for example, the blood plasma substitute perftoran. In theory, the lungs can be filled with this bluish liquid and, saturating it with oxygen, pump it through pumps, providing breathing without any gas mixture at all. However, this method remains deeply experimental; many experts consider it a dead end, and, for example, in the USA the use of perftoran is officially prohibited.
Therefore, the partial pressure of oxygen when breathing at depth is maintained even lower than usual, and nitrogen is replaced with a safe and non-euphoric gas. Light hydrogen would be better suited than others, if not for its explosiveness when mixed with oxygen. As a result, hydrogen is rarely used, and the second lightest gas, helium, has become a common substitute for nitrogen in the mixture. On its basis, oxygen-helium or oxygen-helium-nitrogen breathing mixtures are produced - helioxes and trimixes.
Deeper than 80 m
Complex mixtures It is worth saying here that compression and decompression at pressures of tens and hundreds of atmospheres takes a long time. So much so that it makes the work of industrial divers - for example, when servicing offshore oil platforms - ineffective. The time spent at depth becomes much shorter than long descents and ascents. Already half an hour at 60 m results in more than an hour of decompression. After half an hour at 160 m, it will take more than 25 hours to return - and yet divers have to go lower.
Therefore, deep-sea pressure chambers have been used for these purposes for several decades. People sometimes live in them for whole weeks, working in shifts and making excursions outside through the airlock compartment: the pressure of the respiratory mixture in the “dwelling” is maintained equal to the pressure of the aquatic environment around. And although decompression when ascending from 100 m takes about four days, and from 300 m - more than a week, a decent period of work at depth makes these losses of time completely justified.
Methods for prolonged exposure to high-pressure environments have been developed since the mid-twentieth century. Large hyperbaric complexes made it possible to create the required pressure in laboratory conditions, and the brave testers of that time set one record after another, gradually moving to the sea. In 1962, Robert Stenuis spent 26 hours at a depth of 61 m, becoming the first aquanaut, and three years later, six Frenchmen, breathing trimix, lived at a depth of 100 m for almost three weeks.
Here, new problems began to arise associated with people's long stay in isolation and in a debilitatingly uncomfortable environment. Due to the high thermal conductivity of helium, divers lose heat with each exhalation of the gas mixture, and in their “home” they have to maintain a consistently hot atmosphere - about 30 ° C, and the water creates high humidity. In addition, the low density of helium changes the timbre of the voice, seriously complicating communication. But even all these difficulties taken together would not put a limit to our adventures in the hyperbaric world. There are more important restrictions.
Below 600 m
Limit In laboratory experiments, individual neurons growing “in vitro” do not tolerate extremely high pressure well, demonstrating erratic hyperexcitability. It seems that this significantly changes the properties of cell membrane lipids, so that these effects cannot be resisted. The result can also be observed in the human nervous system under enormous pressure. He begins to “switch off” every now and then, falling into short periods of sleep or stupor. Perception becomes difficult, the body is seized with tremors, panic begins: high-pressure nervous syndrome (HBP) develops, caused by the very physiology of neurons.
In addition to the lungs, there are other cavities in the body that contain air. But they communicate with the environment through very thin channels, and the pressure in them does not equalize instantly. For example, the middle ear cavities are connected to the nasopharynx only by a narrow Eustachian tube, which is also often clogged with mucus. The associated inconveniences are familiar to many airplane passengers who have to tightly close their nose and mouth and exhale sharply, equalizing the pressure of the ear and the external environment. Divers also use this kind of “blowing”, and when they have a runny nose they try not to dive at all.
Adding small (up to 9%) amounts of nitrogen to the oxygen-helium mixture allows these effects to be somewhat weakened. Therefore, record dives on heliox reach 200-250 m, and on nitrogen-containing trimix - about 450 m in the open sea and 600 m in a compression chamber. The French aquanauts became - and still remain - the legislators in this area. Alternating air, complex breathing mixtures, tricky diving and decompression modes back in the 1970s allowed divers to overcome the 700 m depth bar, and the COMEX company, created by students of Jacques Cousteau, made the world leader in diving maintenance of offshore oil platforms. The details of these operations remain a military and commercial secret, so researchers from other countries are trying to catch up with the French, moving in their own ways.
Trying to go deeper, Soviet physiologists studied the possibility of replacing helium with heavier gases, such as neon. Experiments to simulate a dive to 400 m in an oxygen-neon atmosphere were carried out in the hyperbaric complex of the Moscow Institute of Medical and Biological Problems (IMBP) of the Russian Academy of Sciences and in the secret “underwater” Research Institute-40 of the Ministry of Defense, as well as in the Research Institute of Oceanology named after. Shirshova. However, the heaviness of neon showed its downside.
It can be calculated that already at a pressure of 35 atm the density of the oxygen-neon mixture is equal to the density of the oxygen-helium mixture at approximately 150 atm. And then - more: our airways are simply not suitable for “pumping” such a thick environment. IBMP testers reported that when the lungs and bronchi work with such a dense mixture, a strange and heavy feeling arises, “as if you are not breathing, but drinking air.” While awake, experienced divers are still able to cope with this, but during periods of sleep - and it is impossible to reach such a depth without spending long days descending and ascending - they are constantly awakened by a panicky sensation of suffocation. And although the military aquanauts from NII-40 managed to reach the 450-meter bar and receive well-deserved medals of Heroes of the Soviet Union, this did not fundamentally solve the issue.
New diving records may still be set, but we have apparently reached the final frontier. The unbearable density of the respiratory mixture, on the one hand, and the nervous syndrome of high pressure, on the other, apparently put the final limit on human travel under extreme pressure.