HYPOXIA Hypoxia a condition resulting from insufficient supply of tissues of the body with oxygen and / or violation of its assimilation during biological oxidation. A synonym for "hypoxia" are "oxygen starvation" and "hypoxia." In other cases terminological element oxy interpreted as referring to the oxidation (from the English oxydation - oxidation). In this embodiment, the term "hypoxia" is used in a broad sense: Hypoxia a typical pathological process that develops as a result of failure of biological oxidation, which leads to disruption of energy supply functions and plastic processes in the body. Such an interpretation of the term "hypoxia" refers to absolute or relative deficiency of the real level of energy compared to the level of functional activity and intensity of plastic processes in organs, tissues, body. This condition leads to disruption of vital activity of the whole organism, disorders of organs and tissues. Morphological changes in them have a different scope and degree, up to cell death and destruction of non-cellular structures. Hypoxemia Hypoxia (in any version of interpretation) is often combined with hypoxemia. Hypoxemia - a decrease compared with the proper voltage levels and the oxygen content in the blood. Anoxia and anoxemia In connection with developing the problem of hypoxia in the experiment (e.g., when using preparations of isolated organs, tissue fragments or cells) commend anoxic - absence of oxygen and usually halting biooxidation - or anoxemia - lack of oxygen in the blood, used for perfusion individual organs, tissues, cells or subcellular structures. In a holistic living organism the formation of these states is impossible. The criteria for classification of hypoxia Hypoxic conditions are classified taking into account different criteria: the etiology, the severity of disorders, developmental rate and duration of hypoxia. ETIOLOGY (Petrov) According to the etiology identify several types of hypoxia, conditionally combined into two groups: exogenous (normo- and hypobaric hypoxia) and endogenous. Exogenous be normobaric and hypobaric. Endogenous can be tissue, breathing (respiratory), cardiovascular (circulatory), blood (hematic), reloading, substrate. PATHOGENESIS (A.D. Ado) 1. Hypoxia associated with the violation of external respiration (exogenous hypoxic hypoxia and respiratory type of hypoxia) 2. Hypoxia associated with the violation of internal breathing (circulatory, hemic, tissue) Severe disorders On the criterion of the severity of disorders of vital activity distinguishes between the following types of hypoxia: an easy, medium (moderate), heavy, critical (life-threatening, lethal). The main features of a particular expression (gravity) is used hypoxia following: • the degree of violation of neuro-psychic activity, • severity of disorders of the cardiovascular and respiratory systems, • the amount of deviation indicators gas composition and acid base balance of blood, as well as some other factors. Rate of occurrence and duration According to the criteria of rate of occurrence and duration of hypoxic state allocate some of its varieties. Lightning Lightning hypoxia develops within a few seconds. Typically, after a few tens of seconds (within the first minute) after exposure to hypoxia causes of heavy patient's condition is detected, often serving as the reason for his death, for example, depressurization of aircraft on a large, over 9000-11 000 m altitude, or as a result of the rapid loss large amounts of blood, for example, in wounds or major arterial aneurysm rupture their walls. Acute Acute hypoxia develops within a few minutes (usually within the first hour) following exposure to hypoxia causes (e.g., as a result of acute blood loss or acute respiratory failure). Subacute Subacute hypoxia is formed within a few hours (but within the first day). Examples of such species may be hypoxic conditions, developing as a result of ingestion of methemoglobinoformation (nitrates, nitrogen oxides, and benzyl), venous bleeding slowly increasing respiratory or heart is not enough. Chronic Chronic hypoxia develops and / or lasts more than a few days (weeks, months, years), such as chronic anemia, cardiac or respiratory failure. Etiology and pathogenesis of different types of hypoxia Exogenous TYPES hypoxia Exogenous types of hypoxia include normo- and hypobaric hypoxia, the reason for their development: reducing the partial pressure of oxygen (pO2) in the air enters the body. • In the normal barometric pressure talk about exogenous normobaric hypoxia. • With a decrease in barometric pressure known as hypobaric hypoxia exogenous. Normobaric exogenous hypoxia Normobaric hypoxia exogenous reasons: limiting intake of oxygen from air at normal barometric pressure. These conditions are formed when: • Finding people in the small and / or poorly ventilated space (room, mine, well, the elevator). • Violation of the regeneration air and / or supply oxygen mixture to breathe in deep and flying machines, self-contained suits (astronauts, pilots, divers, rescue workers, firefighters). • Failure to observe ventilation techniques. Hypobaric hypoxia exogenous Reasons exogenous hypobaric hypoxia: reduced barometric pressure rise to the height (a 3 000-3 500 m, where pO2 air reduced to about 100 mm Hg) or in the pressure chamber. Under these conditions may develop either a mountain or altitude or decompression sickness. Mountain sickness occurs when climbing into the mountains where the body is exposed not only to a reduced oxygen content in the air and reduced barometric pressure, but also more or less pronounced physical load, cooling, high insolation and other factors, medium and high altitudes. Altitude sickness occurs in people, raised to great heights of public aircraft, on the chairs- lifts, and when the pressure in the chamber. In these cases, the body are substantially reduced pO2 in the inspired air and the barometric pressure. Decompression sickness occurs when a sharp decrease in barometric pressure (eg due to depressurization of aircraft at an altitude of 10 000 -11 000 m). This forms a life-threatening condition characterized by mountainous and high-altitude sickness or acute fulminant. The pathogenesis of exogenous hypoxia The main pathogenesis of exogenous hypoxia (regardless of the cause) include arterial hypoxemia, hypocapnia, gas alkalosis acidosis alternated; hypotension, combined with hypoperfusion of organs and tissues. Reduced oxygen tension in the plasma of arterial blood (arterial hypoxemia) – initial and the main link exogenous hypoxia. Hypoxemia leads to a decrease in oxygen saturation of Hb total oxygen content in the blood and as a result - a violation of gas exchange and metabolism in tissues. Reducing the voltage levels of carbon dioxide (hypocapnia). It is the result of compensatory hyperventilation lungs (due to hypoxemia). The gas is the result of alkalosis hypocapnia. However, it should be remembered that the presence in the inhaled air of high carbon dioxide content (for example, when breathing in a confined space or in a production environment) exogenous hypoxemia can be combined with hypercapnia and acidosis. Moderate hypercapnia (unlike hypocapnia) does not aggravate hypoxia exogenous influences, but rather increases the blood circulation in the vessels of the brain and heart. However, a significant increase in the pCO2 in blood leads to acidosis, ion imbalance cells and biological fluids, hypoxemia, decrease in oxygen affinity of Hb and several other pathogenic effects. Reducing systemic blood pressure (hypotension), combined with tissue hypoperfusion, largely a consequence of hypocapnia. CO2 is one of the main factors of the regulation of vascular tone brain. A significant decrease in PaCO2 is a signal to the narrowing of the lumen of arterioles of the brain, the heart and reduce their blood supply. These changes are the cause of significant disorders of vital activity, including the development of syncope and coronary insufficiency (angina manifested, and sometimes - myocardial infarction). In parallel with these abnormalities are detected violations of the ion balance in cells and in body fluids: extracellular, plasma levels (hypernatremia, hypokalemia and hypocalcemia), lymph, cerebrospinal fluid. The above-described deviation can be reduced or eliminated by adding to the inspired air required (calculation) the amount of carbon dioxide. Endogenous TYPES hypoxia Endogenous hypoxic conditions in most cases are the result of pathological processes and diseases resulting in inadequate oxygen transport to the organs, the metabolism of substrates and / or the use of their tissues. Hypoxia of varying intensity and duration may also develop as a result of a sharp increase in the body's need for energy due to the significantly increased workload (eg, with a sharp increase in physical activity). However, even the maximum activation of oxygen transport and energy is produced systems are not able to eliminate the energy deficit (hypoxia overload). Respiratory hypoxia The cause respiratory (respiratory) hypoxia - lack of gas exchange in the lungs - respiratory failure. Pathogenesis The development of respiratory failure can be caused by alveolar hypoventilation, decreased blood perfusion lung violation of diffusion of oxygen through the air-blood barrier, the dissociation of ventilation-perfusion ratio. Regardless of the origin of respiratory hypoxia pathogenetic link is an initial arterial hypoxemia, is usually associated with hypercapnia and acidosis. Alveolar hypoventilation