PATHOPHYSIOLOGY OF EXTERNAL BREATHING. HYPOXIA

1. PATHOPHYSIOLOGY OF EXTERNAL BREATHING. HYPOXIA Professor Yu.I. Bondarenko

3. Respiratory insufficiency – it is such pathological state, when the tension O2 in blood arterial is reduced (arterial hypoxemia) and the tension CO2 exceeds 50 mm Hg (hypercapnia). Most just characteristic of respiratory insufficiency is degree arterial hypoxemia. • Many specialits consider as respiratory insufficiency also such state, when the respiratory parameters of blood are within of physiological variation, but it is provided with excessive action of external breath, which exhausts and limits reserve possibilities of an organism.

7. In pulmonary function studies a number of abbreviations and symbols have become standardized. Some frequently used ones are listed in the table below: VT tidal volume PO2 partial pressure of O2 FRC functional residual capacity PaO2 PO2 in arterial blood ERV expiratory reserve volume PAO2 PO2 in alveolar gas RV residual volume PCO2 partial pressure of CO2 IC inspiratory volume PaCO2 PCO2 in arterial blood IRV inspiratory reserve volume PACO2 PCO2 in alveolar gas TLC total lung capacity RQ respiratory exchange ratio FEV1 forced expiratory volume in 1s SO2 % saturation of blood with O2 V'O2 amount of consumed O2 SaO2 SO2 in arterial blood V'CO2 amount of produced CO2 DLO2 diffusing capacity of the lung for O2 Raw airway resistance DLCO diffusing capacity of the lung for CO

28. Forms of respiratory insufficiency • Acuterespiratory insufficiency • Chronic respiratory insufficiency

29. Acute respiratory insufficiency • Acute respiratory insufficiency • it issuch state, when syndrome develops fast, within minutes, of hours or day and has tendency to progress. • Fast develops arterial hypoxemia, hypercapnia, develops acidosis, there are disorders of the central nervous system. All this can be completed coma and death.

30. Asphyxia • This state, threatening for life, when in blood don’t enter oxygen, and from blood the carbonic gas is not removed • Asphyxiaoccurs, as a rule, owing to sharp contraction or complete closing of respiratory ways. • a) external compression of respiratory ways; • b)presence in its of foreign bodies; • c) narrowing larynx (allergic edema); • d)presence in respiratory ways and alveolars of liquid (sink, aspiration of vomit mass); • e)swelling of lung; • f) double-side pneumothorax. • g) strong oppression of respiratory centre; • h)disturbance of impulses transfer in neuro-muscular synapses (on respiratory muscles); • i) traumas of thorax • Duration acute asphyxia the person – 3-4 mines

31. Three periods in course of asphyxia • The first period is characterized: • a) excitation of respiratory centre; • b) increase of cardiac rate and increase of arterial pressure. The excitation of respiratory centre is stipulated, mainly, accumulation in an organism of carbonic gas, which acts directly and reflective. Some significance in stimulation of breath has oxygen tension in blood and irritation of aorta and sinoauriculares zones chemoreceptors. • In the beginning of the first period breath has character of inspiratory dispnea when the breath prevails above an exhalation. • At the end of the first period the breath is delayed, and begin to prevail powerful expiration movement (expirational dispnea). The increase of arterial pressure also is explained by delay of CO2

32. The second period of asphyxia is characterized by predominance of the parasympathetic nervous system. • a) breath becomes significant less often; • b) cardiac rate decreases; • c) arterial pressure is reduced In the third period • a) oppression both frequency and depth of breath; • b) breath temporarity is stoped (preterminal pause); • c) on background of stop there are some single, more and more low respiratory movements (gasping-breath). • It is explained that after a paralysis of respiratory centre neurons caudal part of medulla oblongata are excited . They also give some respiratory movements before the complete stop of breath

33. The chronic respiratory insufficiency • The chronic respiratory insufficiencyis characterized by slower increase of hypoxemia and hypercapnia, and they do not reach such degree, as of acute insufficiency due to inclusion of compensatory mechanisms (erythrocytosis, increase of hemoglobin in erytrocytes) • It is known, that the external breath is provided with three processes – ventilating lung, diffusion of gases (О2 and CO2) through alveolar wall and perfusion of blood throughlung capillaries. The disorder of any of these processes can serve as the reason of respiratory insufficiency. • In pathogenesis is distinguishedtwo forms of respiratoryinsufficiency – ventilation and alveolar-respiratory

34. Pathogenetic classification of respiratory insufficiency • Ventilative • Diffusive • Perfusive • Combined

35. Ventilative respiratoryinsufficiency • Obstructive • Restrictive • Dysregulative (disorder of central regulation of breath)

36. Ventilative respiratory insufficiency • The essence of ventilative insufficiency is that in thealveolars for unit time enter less air than in norm. This state is called alveolarhypoventilation. Outlung reasonsof ventilative insufficiency: • Disturbance of respiratory centre function a) effects of medical drugs; b) cerebral-brain traumas with epidural or subduralhematoma; c) malignant tumors of brain; d) absceses of brain, meningitis; e) disorder of brain circulation blood. • Disorder of the motoneurons function of spinal cord, which innervation respiratory muscles (tumor of spinal cord, syringomyelia, poliomyelitis).

37. Ventilative respiratory insufficiency • Disorder of innervation of breathing muscles: а) lesion of nerves – due to avitaminosis, inflammation, trauma; b) blockade of impulses transfer in nervous – muscular synapses – myasthenia, action of myorelaxantes; c) lesion of respiratory muscles-myositis, dystrophies, periodic paralysis, hypocaliemia, hypophosphoremia. • Limitation of thorax mobility: a) inherent or ecquired deformation of ribs and vertebral; b)ossification of costales cartilages; c) grown of preular parts, ascites, meteorism, obesity; d) pain due to neuralgia of intercostales nerves. • Disorder of thorax integrity and pleural cavity (pneumothorax).

38. Obstructive insufficiency • Obstruction of respiratory ways is narrowing their lumen and increase of resistance to movement of air • The damage can be located in upper respiratory ways (with diameter of 2 mm and more) and in lower respiratory ways (diameter – up to 2 mm)

39. Obstructive respiratory insufficiency • Upper respiratory ways is understood cavity of mouth, nasal passage, pharynges, larynges, trachea, large bronchus. • Obstructionit may be is causedinternal and externals mechanical trauma. • Internal traumamost frequently it arises as complication of trachea-intubation, less often – after operation on larynges. • External mechanical trauma – fractures of lower jaw, cervical cartilages, larynges cartilages, epiglossus, trachea, damage of tongue basis, mouth, neck. • The mechanism of obstruction is spasm, edema also paralysis of voice slot, damage or off set of larynges cartilages, hematoma, edema of mucous membrane or serrounding tissues.

40. Internal trauma a) Burns and inhalating of poisoning gases. In these cases develops edema of mucous upper respiratory paths. b) Bleeding in respiratory waysis observed after operation on head and neck, after tonsillectomy, tracheostomy. Sometimes bleeding happens spontaneously, for example from nose. The bleeding especially is dangerous when the patient is in coma or in narcosis, that is when the drainage of respiratory paths is impossible. c)Aspiration of foreign body is observed in children in the age from 6 months to 4 years more often. In the adult aspiration of foreign body occurs, usually, during take food, especially in state of alcoholic intoxication. d) Obstruction lower respiratory ways – necrotic Ludvig`s angina (suprogenis necrotic flegmona of oral bottom cavity of an infectious origin), subpharynges abscess, which is caused aerobic and anaerobic microflora, аngioneurotic edema, which develops as response on allergen and is accompanied nettle-rash, asthma, rhinitis.

41. Obstruction of lower respiratory ways • a) liquidaspiration – vomit mass, blood, water; • b)allergy response mainly on medical preparations – antibiotics and protein substitutes. • It develops immediately, during 30 minutes and appears hardly expressed laryngo- and bronchospasm.

42. Obstructive respiratory insufficiency • chronic unspecific diseases of lung • chronic bronchitis • emphysema • bronchoectasis • bronchial astma

43. EMPHYSEMA • Emphysemais an illness, in which rupture interalveolar septums and lungs capillaries. By basis it is considered degraded collagen and elastic fibres of proteolytic enzymes, which areproduced phagocytes under influence of the external factors – microorganisms, dust particles, tobacco smoke. • In etiology of emphysema some role is attached importance of hereditary predisposition due to synthesis of defective collagen and elasthyne, insufficient synthesis of proteolytic enzymes inhibitors. • The mechanism of obstruction due to emphysema Walls of bronchioles very thin and pliable. The lumen them is supported transpulmonaris more pressure. The more elasticity lung, the should be transpulmonaris more pressure to overcome elastic recoil. Bronchioles for want of that will be in an extended state. When the elasticity lung is reduced, it is enough for their stretch low transpulmonaris pressure. The force, which acts on walls bronchioles from within, decreases and also their lumen is narrowed. The decrease of lumen conducts to sharp increase of resistance to movement of air. As a result of it the breath is difficulty. But even more exhalation is difficulty. For want of emphysema it becomes active. The pressure in pleural cavity increases, and bronchioles are compressed from the outside of lungs fabric. With the cource of time bronchioles compress completely, and the exhalation becomes impossible. Air becomes isolated in alveoles.

44. The mechanism of obstruction dueto bronchial asthma • a) аccumulation of viscous glasslike mucus in bronchus. It is connected with hypertrophy of mucous glands and hyperproduction by them mucus (hypercrinia). The viscous mucus is difficultly discharge and congest (mucostasis). The important role in the mechanism of mucostasis plays hyperplasia of goblet cells, which substitudecells of ciliated epithelium. • b) edemaof mucous, spasm of smooth bronchusmuscules. • c)increased reactivity of bronchial muscles on specific and unspecific stimulus. The highest degree hyperreactivity is observed at once time or after an attack. Strong stimulus, which provokes bronchoconstriction in the patients of bronchial asthma, is the physical load.

45. Restrictive insufficiency • This form of respiratory insufficiency arises, when the extensibility lung is reduced, that is when it not capable easily to be straightened. • To carry out a breath, it is necessary to increase transpulmonary pressure, and it can be made at the expense of increase of respiratory muscles action

46. Restrictive insufficiency a) inflammation and lung edema. b) arterial, venous hyperemia and swelling of interstitial tissue the alveoles is compressed the outside and completely are not straightened. c) lung fibrose, that is growth up rough fibrose connective tissue on place perished elements of parenchyma, elastic fibres and capillaries. d) disturbance of surfactant system. Under surfactant is understood surface-active substances, which reduce a surface tension in an alveole. Influencing on a surface tension, surfactant regulates elastic recoil of lung. As the major function it is necessary to consider prevention of alveolares collapse. It acts as the antistick factor, providing stability of alveole.

47. The deficiency of surfactant • Insufficient synthesis it or excessive remove from a surface of alveoles. The insufficient synthesis is characterized for illness of hyaline membranes in newborn, for want of which destroy intraalveolares septum and in alveoles is stored hyaline with epithelial cells and blood form elements. • Ecquired decrease of surfactant is observed due to asphyxia, acidosis, pneumonia, pollution of air. The defect of surfactant predetermines high surface tension of alveoles and high resistance lung for want of expansion by their inhaled air. • Besides, by cause of restrictive insufficency may be аthelectasis( fall of alveoles and stopping of their ventilation), рneumothorax, deformation of thorax, paralysis of respiratory muscles.

48. Disregulative respiratory insufficiency • Respiratory center dysfunction a) hypoxia b) hypoglycemia c) brain trauma d) compression (edema, tumor, hematoma) e) disorder of brain circulation f) intoxication (narcotic, muscarine, toxic metabolic product) g) inflammation and dystrohpy • Disorder of impulse transmission to the respiratory muscle

49. Disorder of the central regulation of breath • Influence of reflex and humoral factors • Direct influences on the respiratory centre changes function. • Those disorders of breath regulation, which limit alveolar ventilation, can serve as the reason of respiratory insufficiency.

50. Breath disturbances of central genesis. • Bradypnea – rare breath. It can arise reflexly in case of arterial pressure increase(reflex from baroreceptors of aorta and carotide bodies), and also due to hyperoxia (reflex from hemoreceptors of the same zones). • The deep and rare breath arises due to narrowing of upper respiratory ways. It is namedstenotic. • The reason of the bradypnea is a direct lesion of neurons of respiratory centre due tolongtime hypoxia, under influence of narcotic, due to organic changes in a brain (inflammation, insult) or functional disorders of the central nervous system (neurosis, hysteria)