For a sailor who is overboard, a great danger is the hypothermia of the body in water or hypothermia. It should be noted that the hypothermia of the body in water can lead a person to death even when he is exposed to the damaging effects of the cold while on life-saving equipment.
Hypothermia of the human body in water, cold shock, dangerous water temperature, negative effects of cold water on the human body.
It has been established that lowering body temperature below the physiological minimum leads to impaired functions of the brain, skeletal muscles, and heart. Signs of overcooling of the human body appear in a certain sequence, reflecting a decrease in the temperature of the internal environment of the body.
Muscle tremors appear when the temperature in the rectum decreases from 37 to 36 degrees. Trembling – an asynchronous contraction of muscle fibers – represents the body’s reserve in maintaining temperature. It quickly rises to the maximum and shakes the body of a person who is in the water for 20-30 minutes, and then gradually fades away. The temperature of the internal environment of the body continues to decline.
Any movement of a person begins to be accompanied by muscle pain. When the temperature in the rectum reaches approximately 35 degrees, dysfunction of the brain occurs. Drowsiness appears, indifference to the environment, a false sense of comfort. Consciousness fades when the temperature drops to 32–31 degrees. When it falls to 29–28 degrees, breathing and palpitations cease.
Based on the materials about the circumstances of the death of people who suffered a disaster at sea in various climatic and geographical areas, experts argue that the estimated terms of survival and salvation of people can be no more than those indicated in the table below. It has been established that life-threatening cooling of the body does not occur even with a prolonged stay in water with a temperature of plus 33 degrees, so staying in it is not limited.
Estimated time of survival and time of rescue of the victims of the disaster at sea depending on the water temperature.
As can be seen from the above data, the duration of a person’s stay in relatively warm water is safe even for several tens of hours, but even in these conditions he can die from the action of the whole complex of unfavorable factors. Hypothermia, overfatigue, depletion and dehydration of the body as a result of cold diuresis – increased urination under the influence of hypothermia.
Cold shock with prolonged exposure to cold water.
Often death can overtake a person who finds himself in water having a temperature below 10 degrees, much earlier than a general hypothermia occurs. The cause of death will be the rapid development of cold shock (general shock).
Cold water in this case acts not only as a medium with a very high heat capacity (4.2 times more than the heat capacity of air) and heat conductivity (28.7 times more than the heat conductivity of air), but also as a strong thermal stimulus causing vascular collapse (sharp weakening) blood circulation), especially in non-hardened people.
The development of cold shock is facilitated by: overheating of the body (prolonged exposure to the sun, work in the engine room, etc.) before getting into cold water, a state of chills, rapid immersion in water without gradual adaptation. At the same time, the victim, falling into the water, immediately loses consciousness and drowns, without taking any action to his rescue.
Negative effects of cold water on the human body.
Water with a temperature of 12 degrees or lower was found to cause periodic (every 15-30 minutes) expansion of spasmodic vessels of the skin (Lewis phenomenon). This significantly reduces the effectiveness of the vasomotor (vasomotor) reaction aimed at regulating heat transfer with the environment. Intensive hypothermia of the human body dramatically stimulates metabolic processes.
In this case, the human body consumes easily digestible energy substrates, such as carbohydrates and free fatty acids, than under normal air conditions. Hyperglycemia (an increase in the amount of sugar in the blood), developing as a result of stress, in the compensation phase, as energy resources are depleted, is replaced by increasing hypoglycemia (a decrease in the concentration of glucose in the blood).
Energy resources practically do not have time to be used up only in cases of death from a cold shock. With acute cooling in water, rapid development of bradycardia (slowing of cardiac activity), as well as a violation of the rhythm and depth of breathing, are observed.
Against the background of a large oxygen demand of the body associated with the activation of thermoregulatory metabolism (metabolism in the body), these changes from the respiratory and cardiovascular systems significantly reduce the level of blood oxygenation (oxygenation of arterial blood) and thereby accelerate the development of hypoxia (decrease in oxygen content) in the blood) in the body.
The sudden action of cold water can cause respiratory distress (respiratory arrest, suffocation) or heart rhythm as a result of extensive irritation of cold skin receptors. Causing a rapid decrease in skin temperature, especially limbs, cold water causes a loss of tactile (skin) and pain sensitivity, as well as a sharp decrease in muscle strength.
Research and experience in rescuing the crews of dead ships showed that a person after 1-2 minutes in cold water is not able to independently climb a lifeboat or raft.
Serious mental disorders are characteristic of acute cooling in water, which proceeds as a stress response to an intense stimulus. They dramatically reduce the body’s ability to combat the cold. When swimming at the water surface in an oblique-vertical position, the menacing effect of cold affects not only the vasomotor centers of the spinal cord of the victim, but also directly on his blood vessels.
As a result, this leads to a rapid depletion of the functional capabilities of the cardiovascular system. Therefore, the death of supercooled in water does not occur from an initial respiratory arrest, as happens under normal conditions on land, but from acute heart failure (collapse, cardiac arrest), which often occurs against a background of hypoglycemic coma (unconscious state). All of the above greatly complicates the salvation of man.
Resistance of the human body to the cooling effect of cold water.
It should be noted that resistance to the cooling effect of water is very individual. According to the Medical Research Council of Great Britain (an organization that deals with the fate of shipwrecked and seeks to reduce the number of victims on the high seas), during World War II, there were many cases where people managed to be saved after 60 minutes in the water, the temperature of which was lower 0 degrees, and after 1.5 hours in water with a temperature of plus 1-3 degrees.
Of the 40 people recovered after 1 hour from the water (temperature plus 1.7 degrees), 9 died on board a rescue ship. 1 sailor managed to hold out in water (temperature plus 1.7-3 degrees) for 20 minutes. 6 people survived after staying in water (temperature plus 5) 30 minutes. 2 sailors lasted in the same water for 1.5 hours. 17 people stayed in water (temperature plus 7) for 30–45 minutes. 2 sailors stayed in water at a temperature of plus 8 degrees for 2 hours. One of them was saved, the other died in a lifeboat. One lucky man managed to stay alive after he swam in water at a temperature of plus 8 degrees for 12 hours!
Amazing cases of rescuing people caught in icy water.
Amazing cases of saving people who, by the will of fate, find themselves in icy water. January 19, 1965 in the southeastern part of the Bering Sea turned over from icing and sank four Soviet trawlers: Sevsk, Sebezh, Nakhichevan, Boksitogorsk. It happened 100 miles from St. Matthew Island and 60 miles from St. Paul Island.
The only one who managed to escape was the trammaster A. Okhrimenko. He survived for several hours in water with a temperature close to the freezing point, with a 10-point storm and frost minus 21 degrees. This case is unique in the history of disasters at sea..
In 1986, a boat with 4 Icelandic fishermen suddenly turned over. At the same time, 3 of them managed to grab the keel. Water temperature did not exceed plus 5 degrees. After holding on for 45 minutes, they were all forced to swim to shore. But after 10 minutes, 2 drowned. And only the third managed to overcome 5 km to the saving coast in 5 hours. The 23-year-old fisherman was 195 cm tall, weighed 125 kg and was dressed only in a shirt and jeans. Doctors classify this case as phenomenal in medical practice..
It has been established that resistance to hypothermia is higher in people with a pronounced subcutaneous fat layer and in athletes trained to swim in cold water. American researchers Pu and Edholm (1955) demonstrated this by suggesting to 2 swimmers, one of whom was unaccustomed to cold water, and the other – trained walrus, to swim in water plus 16 degrees “to failure”.
The first was forced to land on land after 30 minutes. He was shaking, movements hurt. The temperature in the rectum decreased to plus 34.5 degrees. The second subject was in the water for 6 hours 40 minutes. I felt good. He did not have a decrease in body temperature. By applying tempering procedures that are regularly performed over a long period of time, a high degree of resistance to cold water can be achieved..
Modern records of swimming in cold water.
In 1987, the 30-year-old American L. Cox conquered the coolest of the coldest straits – the Bering. She overcame 7 km, spending 2 hours 50 minutes in water, which has a temperature of just plus 7 degrees! In 1988, a brave athlete again surprised the world. For 4 hours 18 minutes she sailed on Lake Baikal for almost 16 km at a water temperature of 9-10 degrees. No one on the planet has succeeded like this..
It should be noted one more exceptional achievement of the fair sex. In 1985, she realized the fantasy of Jules Verne – in 80 days she sailed around the world!
Based on the book Encyclopedia of Survival at Sea.