Hypoxia. (Subject 7) презентация

Hypoxia July 24, 2017

Hypoxia classification

Hypoxia classification Due to time of development Fulminant (immediate) –several seconds (cyanide poisoning). Acute – several minutes (cardiac arrest). Subacute – several hours or days (respiratory failure). Chronic – months and years.

Hypoxia classification Due to prevalence of clinical symptoms: local and general. Due to the severity of pathological process: light; moderate; severe; critical (lethal) hypoxia.

Exogenous (hypoxic) hypoxia hypobaric type  atmospheric pressure+ partial oxygen pressure in the air Mountain sickness factors: low partial pressure of oxygen, low barometric pressure, physical loading, cooling, increased exposure to UV rays. Altitude sickness factors: low barometric pressure and low partial pressure of oxygen

Exogenous (hypoxic) hypoxia normobaric type Normal atmospheric pressure + oxygen % in the air: - in small rooms with bad ventilation (elevators, mines, mineshafts); - in divers, when there are problems with aqualung function; - incorrect conduction of artificial lungs ventilation during surgical operations.

Exogenous (hypoxic) hypoxia

Exogenous (hypoxic) hypoxia

Respiratory hypoxia

Respiratory hypoxia Alveolar hypoventilation reasons: Obstructive violations (lung edema, tumors or foreign bodies in the lumen of bronchi and bronchioles). Restrictive violations (chronic inflammatory or sclerotic processes in the lungs and in the chest). Disturbances of respiratory regulation (toxic substances poisoning, brain trauma).

Respiratory hypoxia Disturbances of lungs blood supply - heart failure, decreased circulating blood volume (after blood loss). Disturbances of gases diffusion in lungs chronic inflammatory diseases of the lungs, lungs edema. Blood indices: low oxygen, high CO2, low pH (acidosis)

Circulatory hypoxia

Circulatory hypoxia - systemic Decrease of heart activity - myocardial infarction, myocarditis. Hypovolaemia - severe blood loss, dehydration of the organism after burns, cholera, vomiting. Vascular disorders (low vascular tone) - shock, collapse, aldosterone deficiency.

Circulatory hypoxia Local type of circulatory hypoxia -insufficient blood supply of the organ or tissue (ischemia) or the difficulty of venous outflow (venous hyperemia, stasis). Blood indices: normal oxygen in arterial blood, low oxygen in venous blood, low pH (acidosis).

Hemic hypoxia Anemic type – accompanying different anemias. Inactivation type - poisoning with CO, nitrates, sulfonamides and other substances that yield in methemoglobin formation Blood indices: low O2 in arterial and venous blood, non-gaseous acidosis.

Hemic hypoxia The reasons of anemia: chronic bleedings, erythrocytes hemolysis, depression of erythropoiesis.

Hemic hypoxia Carbon monoxide poisoning: CO has the affinity to Hb 300 times higher than O2 Carboxy-Hb (HbCO) is formed (stable substance) Symptoms: drowsiness and headache, unconsciousness, respiratory failure, and death.

Histotoxic hypoxia The inability of cells to utilize oxygen Causes: tissue poisoning (alcohol, narcotics, cyanide). biological oxidation enzymes inhibition and the disturbance of their synthesis; the damage of membrane structures of the cell.

Histotoxic hypoxia Cyanide poisoning Cyanide ions bind to the Fe atom of cytochrome C oxidase The ATP synthesis stops. Nervous system and the heart are particularly affected.

Histotoxic hypoxia Disturbance of respiratory enzymes synthesis results from vitamins deficiency (B group vitamins, pantothenic acid). Damage of mitochondrial membranes and other cellular elements (radiation injury, over-heating, intoxication, infection, cachexia, uremia). Blood indices: the pressure, saturation and content of O 2 in blood are near normal.

Histotoxic hypoxia Dissociation of oxidation and phosphorylation processes in respiratory chain: energy is dispersed as a heat. ATP synthesis is low. The factors: hormones of thyroid gland, excess of Ca, toxins.

Overload hypoxia Occur during physical overload of certain organ or tissue. It is observed in skeletal muscles and myocardium. Blood indices: arterial and venous hypoxemia and hypercapnia. Local heart hypoxia may transform to secondary general circulatory hypoxia In the excessive muscular work - bloodflow in the muscles is increased ischemia of other tissues.

Substrate hypoxia Deficiency of the substrate to be oxidized - glucose Carbohydrate starvation and hypoxia of insulin-dependent tissues often occur during diabetes mellitus.

Combined hypoxia It is a combination of 2 and more main types of hypoxia.

Combined hypoxia

Disturbances in the Organs and Physiological Systems Nervous system – emotional and motion excitation, inadequate behavior; disturbances of reflex activity and regulation of breathing and blood circulation; loss of consciousness and convulsions. Heart and vessels – tachycardia, arrhythmia, low BP.

Disturbances in the Organs and Physiological Systems Lungs - irregular breathing; decreased diffusion of oxygen from the alveolar air to blood. Liver (chronic hypoxia) - disturbance of all kinds of metabolism, inhibition of detoxication, decreased synthesis of substances.

Disturbances in the Organs and Physiological Systems GIT organs (chronic hypoxia) - violation of appetite, inhibition of peristalsis and secretion, development of erosions and ulcers. Immune system (chronic hypoxia) - low functional activity of the immune cells and innate immunity factors.

Adaptation to hypoxia The reactions of urgent adaptation (protective-adaptive) manifest in acute hypoxia. Permanent -adaptive (compensatory) - during long-term or repeating hypoxic effects.

Urgent adaptation The reason of adaptation - lack of energy supply due to low ATP amount (lack of biological oxidation). Respiratory system -  blood oxygen and  CO2 irritate chemoreceptors. This result in the increase of the alveolar ventilation.

Urgent adaptation Heart – tachycardia,  heart stroke volume and minute blood volume. Vessels - centralization of bloodflow (dilation of the brain and heart arterioles with simultaneous constriction of the arterioles in others tissues and organs).

Urgent adaptation Blood - activation of RBC outflow from the bone marrow and blood depot (liver, spleen). Increased affinity of Hb to oxygen and the degree of oxyHb dissociation in the tissues. Tissues systems of biological oxidation -  anaerobic glycolysis, the activation of respiratory enzymes.

Adaptation to hypoxia Urgent reactions - activation of the oxygen transport to the tissues. Permanent compensation - activation of biological oxidation and structural changes of organs and systems that are transporting oxygen.

Permanent adaptation Lungs - increased surface of alveoli, number of capillaries, rate of gases diffusion through alveoli to vessels. Respiratory muscles - hypertrophy and increased working capacity. Heart - the number of myocardial fibers, capillaries and nerves is increased.  of heart stroke volume and minute volume.

Permanent adaptation Number of the vessels in all organs and tissues is increased. Blood – increased blood cells number due to increased erythropoiesis. Chronic lack of oxygen causes the activation of erythropoietin synthesis in kidneys. Metabolic processes : decrease of metabolism intensiveness; high efficiency of anaerobic glycolisis; prevalence of anabolic processes in the cells.

Clinical application of hypoxia Intermittent hypoxia - repeated episodes of hypoxia interspersed with normoxic periods (Interval Hypoxic Trainings) Hypoxic episodes are created by exposure to natural high altitude, sojourns in hypobaric chambers or by breathing hypoxic gas mixtures in normobaric conditions.

Clinical application of hypoxia Interval Hypoxic Training is used for the treatment of bronchial asthma, chronic obstructive pulmonary diseases, coronary heart disease, arterial hypertension, neurocirculatory asthenia, neurodermitis, diabetes mellitus II type. The method is effective to increase physical and mental working capacity. The counter-indications are: all acute somatic and infectious diseases.

Clinical application of hypoxia Adaptation to hypoxia provides resistance to other stress factors (cross-resistance). Adaptation to hypoxia is characterized with structural and functional changes in many organs and tissues. Body resistance is increased to hypothermia, overheating, physical overstrain, infections