The effect of increased barometric pressure

Unlike local compression resistance to common uniform barometric pressure is very high. The human body can withstand a pressure of more than 6 MPa expressed without mechanical damages.
A General characteristic of influence of high atmospheric pressure on the body is temporary, reversible character of the coming changes in the activity of many organs and body systems.
With the influence on the organism of high barometric pressure person occurs most often in the deep underwater dives. When immersed in water primarily in addition to atmospheric and hydrostatic pressure, which increases as the dive. It is established that the hydrostatic pressure in comparison with atmospheric at a depth of 10 m doubles, 20 m tripled, etc. Increased hydrostatic pressure reduces the sensitivity of the skin receptors to the traumatic effects. Wounded under water are often overlooked and are detected victims only if ascent to the surface. The greatest shift of exposed tissue, limiting cavities and organs, containing air (lungs, gastrointestinal tract, middle ear, and others). Due to the significant difference between external and internal (in tissues and body cavities) pressure is a so-called barotrauma, characterized by damage to hearing apparatus and respiratory system (redness, bleeding in the eardrum, the gap lung tissue, bleeding). Sudden changes in pressure occur during rapid immersion in water or air, especially at malfunction of the gas breathing apparatus. Observations indicated that the cause of death when using aqualungs in 80 % cases is barotrauma lungs and in 20 % of cases of drowning.
It seems appropriate to stress that in surfacing more dangerous is the passing of small depth, because they can see a sharp relative increase intra-lungs pressure. In divers and athletes using underwater mask and breathing tube, pulmonary barotrauma never happens, because when diving volume of air in the lungs is reduced and when the ascent to the surface again reaches of the original value. When afloat, for example, scuba diving dangerous delays at a depth of 10 m from the surface. This leads to a sharp increase in pressure due to increased volume of air in the lungs, which is accompanied different scale discontinuities tissue of the respiratory tract - the bronchi and the alveoli, causing hemorrhages, pneumothorax, gas embolism, interstitial and subcutaneous emphysema.
The greatest danger to the life of the victim is the flow of air into the lumen of a ruptured blood vessels of the small circle of blood and the occurrence arterial gas embolism. Air bubbles, mainly nitrogen, clog many blood vessels of the lungs, brain, heart and other organs, leading to total oxygen starvation of the body. The most common symptom of pulmonary barotrauma are loss of consciousness, respiratory disorders and blood circulation. Of pulmonary barotrauma is also possible in patients with dacha intratracheal anesthesia and carrying out of artificial ventilation of the lungs using a variety of devices.
Barotrauma should be distinguished from decompression sickness, the pathogenesis of which is the formation of gas bubbles in the blood and other tissues occurs without damage to the lungs and blood vessels.
In the study of the corpses of people who have died from pulmonary barotrauma, you must extract from the chest heart and lungs with a bandaged arteries and veins, entering and leaving him to inflate the lungs under water and to identify gaps lung tissue facing air bubbles. Confirmation of the diagnosis of pulmonary barotrauma is the detection of gas emboli in the vessels of the lungs, heart, and brain. The terminating character of coronary vessels contributes embolization and the emergence of disorders of cardiac activity up to a heart attack and cardiac arrest.
In the implementation of diving and decompression of work, the study of the deep sea, as well as in medicine is widely used oxygen under high pressure. Acute intoxication occurs at a relatively short-term exposure of oxygen under pressure of 2.5-3 MPa and above. The defeat of the most affected Central nervous system, so this form is designated as neurotoxic, brain, or seizure (oxygen epilepsy, acute oxides and others). In children, there is a strong resistance to compressed oxygen and less typical for them convulsive form of poisoning. Chronic oxygen toxicity is possible with prolonged (over 2 hours), often repeated exposure to small (1 - 1.5 MPa) oxygen pressure. The leading characteristic are changes pulmonary - pulmonary form (oxygen pneumonia, pulmonary burn, subacute oxides).
Thus, when breathing oxygen pressure of 3 MPa and above the most likely development neurotoxic forms of intoxication, and at pressure 2 MPa and below - pulmonary. At a pressure of 2 to 3 MPa may occur and then, and another defeat.
Early functional morphological manifestations of the action of oxygen under high pressure on the organs and tissues are reduced glycogen content and change of activity of oxidation-reduction enzymes in parenchymal cells. In the heart (myocardium), liver, lungs, kidneys - under the influence of hyperbaric oxygenation certain morphofunctional changes in the parenchyma, stroma and blood vessels. First of all suffer from the walls of blood vessels, especially capillaries, which leads to their increased permeability and disturbance of microcirculation in organs; develops intercellular edema and as a result - malnutrition parenchymal cells. There is stagnant plethora of veins and capillaries.
With a sharp transition from high pressure to normal due to created while the saturation of organism with inert gases occur decompression violations. Gases dissolved in the blood and body fluids, standing out of them, form a loose gas bubbles - gas emboli. Blocked blood vessels bubbles gases causes different symptoms that received the name of decompression sickness (decompression sickness).
When decompression sickness gas bubbles in the free state can be formed not only in blood and lymph vessels, but also in joint cavities, bile, cerebrospinal fluid, very often and in large numbers in adipose tissue and other nitrogen solubility in body fat in 5 times higher than in blood, therefore fatty substances are specific tanks dissolved indifferent gas. Myelin sheath of nerve fibers is also a reservoir of dissolved nitrogen.
In the study of the corpses of people who have died from decompression sickness, show symptoms of gas emboli detected by means of an appropriate sample. In the right half of the heart and the veins are blood convolution with small bubbles of gas. Their accumulation in the subcutaneous tissue leads to the formation of subcutaneous emphysema. The existence of gas can be diagnosed rentgenograficheskie; this method to detect gas bubbles in the carotid arteries. Examination of decompression sickness is always necessary to conduct a comprehensive manner and with the participation of technical experts to clarify the nature of emergency, violations of prevention measures, the chemical composition of inhaled gas mixtures, hardware malfunction and other