PATHOPYSIOLOGY OF THE RESPIRATORY SYSTEM Ph.D., Ivanitsa A.O.

External respiration is a complex of processes occurring in the lung and providing normal contents of oxygen and carbon dioxide in blood. Three main processes take place in the lungs: alveolar ventilation, diffusion of the molecular oxygen and carbon dioxide through the alveolar-capillary membrane and perfusion (flowing of the corresponding amount of the blood via the pulmonary capillary vessels).

Respiratory failure (respiratory insufficiency) – is a pathological state that is characterized by disorder of gas exchange between ambient air and circulating blood and leads to inequality of blood gas composition to an organism oxygen necessity.

Classification of insufficiency of the external breathing according Votchal: a) centrogenic; at the violation of work of the respiratory center (hemorrhage, tumor, depression of CNS at shock); depression of central regulation of breathing as a result of poisoning by narcotic drugs, barbiturates. b) nervous and muscular: violation of activity of respiratory muscles at the damage of spinal cord (trauma, poliomyelitis). .

Classification of insufficiency of the external breathing according Votchal: c) thoracodiaphragmal: violation of biomechanics of breathing is related to pathology of thorax (fractures of ribs, kyphoscoliosis); high standing of diaphragm (paresis of stomach, intestine, ascitis, obesity, pregnancy); hemothorax, pneumothorax. d) bronhopulmonary:-pathological processes in lungs and respiratory tracts: a) obstructive form (bronchospasm, compression by tumor, edema of bronchs); b) restrictive form- at reduction of respiratory surface of alveoli (surfactant insufficiency; pneumonia, pneumosclerosis, emphysema, resection of lungs); c) diffusive form at the thickening of alveolar-capillary membrane (black-lung disease, fibrosis of lungs)

Classification of respiratory insufficiency according to pathogenesis

The indexes of respiratory insufficiency are divided into: 1. direct - change of gas composition of blood: - hypoxemia (decrease of pO2 of arterial blood less than 90 mmHg); - hypercapnia (increase of pCO2 of arterial blood more than 45 mmHg) - gas acidosis 2. indirect - change of lungs volumes (RV, RVinsp., RVex., VLV, MVL)

Classification of pathological types of breathing a) the pathological types of breathing characterized by disorders of the breathing depth and rate: - bradypnoea; - tachypnoea; - dyspnea; - hyperpnoea; b) periodic breathing: - Cheyne — Stokes respiration; - Biot’s respiration; c) terminal breathing: - apneustic respiration; - gasping respiration; - Kussmaul’s respiration.

Bradypnoea is a low respiratory rate.

Tachipnea – is frequent shallow respiration.

Periodical breathing – is pathological breathing that is characterized by the periods of respiration and periods of absence of breathing (apnea). Terminal breathing – is characteristic for the terminal states.

Periodic respiration - Cheyne — Stokes respiration; - Biot respiration.

Kussmaul respiration in the patients in diabetic coma. Terminal respiration Kussmaul respiration in the patients in diabetic coma. Apneustic respiration – is characteristic for inhibition of respiratory center. Gasping respiration is characteristic for agony.

Asphyxia - a life-threatening pathological condition due to acute respiratory failure occurs when O2 does not enter the blood, and CO2 is not excreted from the blood

Causes of asphyxia: 1. compression of the airways (strangulation), 2. blockage in the world of the respiratory tract (foreign bodies, inflammatory edema), 3. The presence of fluid in the respiratory tract and alveoli (drowning, pulmonary edema, aspiration of vomit), 4. bilateral pneumothorax. 5. severe depression of the RC

Periods of asphyxia First period: inspiratory shortness of breath. Rapid increase in depth and frequency of respiration. General excitement develops, ↑ tone of the sympathetic nervous system (pupils are enlarged, tachycardia appears, ↑ AP). Second period: expiratory dyspnea the respiratory rate gradually decreases, the exhalation phase is intensified. The predominant tone of the PSNS: pupils are narrowing, AP ↓, ↓ heart rate. Third period: there is a decrease in the frequency and amplitude of respiration. Gasping breathing appears, after which a breath stops.

Hypoxia – reduction of oxygen supply to a tissue below physiological levels despite adequate perfusion of the tissue by blood.

Classification of hypoxia By etiology: I. Exogenous (hypoxic). II. Endogenous 1. Respiratory (respiratory). 2. Circulatory (cardiovascular). 3. Hemic (blood). 4. Tissue (histotoxic). 5. Mixed.

Classification: Hemic hypoxia  that due to reduction of the oxygen-carrying capacity of the blood owing to decreased total hemoglobin or altered hemoglobin constituents. Histotoxic (tissue) hypoxia  that due to impaired use of oxygen by tissues.

hypoxic hypoxia  that due to insufficient oxygen reaching the blood. respiratory hypoxia  that due to failure to transport sufficient oxygen because of inadequate lungs ventilation. circulatory hypoxia  that due to failure to transport sufficient oxygen because of inadequate blood flow.

Respiratory (breathing) hypoxia causes: alveolar hypoventilation (bronchitis, bronchial asthma, pneumonia, pulmonary edema, pneumo- and hemothorax, etc.) reduction of perfusion of the lungs with blood (↓ Volume of Circulating Blood, insufficiency of the contractile function of the heart, pulmonary hypertension, etc.) difficulty in diffusion of oxygen in the lungs (pulmonary edema, pneumosclerosis, pneumoconiosis, etc.).

Changes in the parameters of the gas state of the blood at respiratory hypoxia: ↓ рО2art - arterial hypoxaemia. ↑ pCO2 art - hypercapnia, which causes the appearance of gas acidosis.

Circulatory (cardiovascular) type Reasons: 1) disorders of general hemodynamics (acute and chronic heart failure , shock, collapse), 2) violation of local blood circulation (ischemia, thrombosis, embolism, stasis, venous hyperemia). Changes in the parameters of the gas state at circulatory hypoxia: ↓ pO2art - arterial hypoxemia. an increase in the arteriovenous difference in oxygen due to its reduction in arterial blood.

Hemic (blood) type of hypoxia Reasons: 1. Reducing the effective oxygen capacity of the blood (anemia, infusion of 0.9% NaCl in large quantities), 2. Inactivation of hemoglobin (violation of bind, transport and give oxygen to tissues). Changes in the parameters of the gas state of blood at hemic hypoxia: pO2 art is normal, pO2 ven reduced Reduced arteriovenous oxygen difference. Acidosis

Tissue (histotoxic) hypoxia causes: 1. Destruction of oxygen in the tissue. 2. Inhibition of biological oxidation. The main enzymes involved in the processes of tissue respiration: cytochrome oxidase, succin dehydrogenase NADP dehydrogenase acyl-CoA dehydrogenas Changes in the gas state of the blood at tissue hypoxia: reduction of arteriovenous oxygen difference. ↑ pO2 of venous blood.

Pathogenetic therapy is based on the rupture of chains of pathogenesis of the hypoxic state or elimination of its main links: antioxidants - agents that suppress free radical oxidation of membrane lipids, which plays an important role in hypoxic tissue damage, and antioxidants, which favorably affect directly the processes of biological oxidation.