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Respiratory Failure

Respiratory Failure. external respiration （ pulmonary ventilation and gas exchange in lung ） transport of gas internal respiration. Respiration. Respiratory failure. concept and classification. respiratory insufficiency

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Respiratory Failure

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  1. Respiratory Failure

  2. external respiration（pulmonary ventilation and gas exchange in lung） • transport of gas • internal respiration Respiration

  3. Respiratory failure concept and classification • respiratory insufficiency • The condition in which the lungs can not take in sufficient oxygen or expel sufficient carbon dioxide to meet the needs of the cells of the body. Also called pulmonary insufficiency.

  4. 2. respiratory failure Respiratory failure is a syndrome in which the respiratory system fails in one or both of its gas exchange functions: oxygenation and carbon dioxide elimination. In practice, respiratory failure is defined as a PaO2 value of less than 60 mm Hg while breathing air or a PaCO2 of more than 50 mm Hg. normal reference values： PaO2< 60mmHg（8kPa） with or without PaCO2 > 50mmHg（6.67kPa） RFI = PaO2/FiO2 ≤ 300

  5. 3．classification （1）according to PaCO2 ■hypoxemic (Group Ⅰ) respiratory failure a PaO2 of less than 60 mm Hg with a normal or low PaCO2. Cause of: Edema, Vascular disease, Chest Wall. ■hypercapnic (Group Ⅱ ) respiratory failure a PaO2 low 60 mm Hg andPaCO2 of more than 50 mm Hg. Cause of: Airway obstruction, Neuromuscular disease.

  6. （2）according to pathogenic mechanism ■ ventilatory disorders ■ gas exchange disorders （3）according to primary site ■ centralrespiratory failure ■ peripheral respiratory failure （4）according to duration ■ acute respiratory failure ■ chronic respiratory failure

  7. respiratory failure ventilatory disorders gas exchange disorders obstructive ventilatory disorders restrictive ventilatory disorders diffusion disorders ventilation-perfusion mismatching etiology and pathogenesis 【classification of respiration failure mechanism】

  8. Ⅰ. ventilatory disorders 1. restrictive ventilatory disorders Restrictive hypoventilation is caused by the diseases that affect the distensibility of the alveolar.

  9. Respiratory movement forced breathing

  10. damage of CNS drug overdose Depression of CNS Respiratory movement ↓ neuro-muscular disorders Respiratory movement disorder decreased strength, myasthenia gravis hypoxia, acidosis alveolar distensibility Restrictive ventilatory disorders respiratory failure ▲ Disorders of the respiratory muscles

  11. ▲decreased lung compliance ●decrease of pulmonary surfactantsand increase of surface tension force ● diffuse interstitial fibrosis ▲decreased thoracic compliance of lung deformity of thorax , fracture of several ribs, tension pneumothorax, thickened constrictive pleural layer.

  12. 原因和机制 2. obstructive ventilatory disorders ■ obstructive ventilatory disorders are caused by the diseases which share the common characterestic of causing enough narrowing within the tracheobronchial tree to increase resistance to the flow of air. ■ etiology asthma, emphysema, chronic bronchitis, and bronchiectasis.

  13. ■Obstruction is located in the airway outside the thorax： inspiratory dysnea ■Obstruction is located in the airway inside the thorax： expiratory dysnea three depression sign 1） central airway obstruction defined as airway obstruction between the glottis and the carina + expire inspire

  14. 2） peripheral airway obstruction smaller airways less than 2 mm in diameter. Determinants of airway closure are the intrinsic caliber of peripheral airways. Smooth muscle tone, thickness of the wall, mechanical properties of the surface film, and secretions in the lumen ,bingding effect of attachments of the surrounding lung parenchyma. equal pressure point (EPP) In forced expiration, the point where intrapleural pressure and alveolar pressure are equal.

  15. Peripheral airway obstruction may be caused by: specific chemical mediators (such as histamine, leukotrienes, prostaglandins ), other substances released during inflammatory and allergic responses. forced expiration EPP moves distally as expiration progresses because as air leaves the alveolar unit, the pressure in the alveolar decreases hence the pressure in the airway decreases as well.

  16. 3. The alteration of blood gas 1）Low PaO2： PaO2 < 60mmHg 2）PaCO2 change： A. hypoventilation：high PaCO2. R=40/50 mmHg=0.8； B. part hypoventilation: Low PaO2 and normal or low PaCO2.

  17. Ⅱ. gas-exchanging dysfunction 1. diffusion disorders The diffusion impairment is characterized by a disruption in the exchange of O2 or CO2 or both across the alveolar-capillary membrane. Causes: reduction and/or thicken of alveolar-capillary membrane or reduction of the diffuse time.

  18. 1） etiology of diffusion disorders ■ reduction of diffusion membrane area Abnormalities of diffusion may not cause arterial hypoxia in persons at rest unless they are extremely severe. (total: 80 mm2; at rest: 30~40 mm2) Causes: emphysema, pneumonia, lobectomy ■ increase of diffusion membrane thickness edema, fibrosis, capillary vessel dilatation ■ decreased time of blood contacts with alveolar

  19. · · · · VA Q VA/ Q Top 1.2L/min 0.4L/min 3.0 Middle 1.8L/min 2.0L/min 0.9 Bottom 2.1L/min 3.4L/min 0.6 2. ventilation/perfusion imbalance The dysfunction of gas exchange can arise secondary to ventilation /perfusion mismatching.

  20. · · 1)type and cause of ventilation-perfusion-mismatching (1) decreasedratio of VA/Q underventilated in relation to their perfusion asthma, chronic bronchitis, obstructive emphysema, fibrosis, edema VA/ Q↓ part alveolar ventilatory ↓ functional shunt↑>30% respiratory failure · ·

  21. · · pulmonary artery embolization, DIC in lung, vessels contract, pulmonary arteritis, dead space like ventilation VA/Q↑ poor perfusion↓ respiratory failure · · (2) increased ratio of VA/Q poor perfusion in relation to their ventilation with air

  22. bronchiectasis anatomic shunt↑ Pulmonary A-V shunt open↑ ▲ increased of anatomical-like shunt pulmonary consolidation,Atelectasis true shunt↑ Respiratory failure anatomical-like shunt 3）increased of anatomical shunt Right-to-left shunts or anatomic shunt ▲increased of anatomical shunt

  23. Ⅲ. Acute respiratory distress syndrome（ARDS） [concept] ARDS is a clinical description of severe lung injury characterized by increased permeability of alveolar-capillary membranes, development of protein-rich pulmonary edema, marked hypoxemia refractory to increase in inspired oxygen concentration, and the absence of left ventricular failure.

  24. [etiology] • shock from any cause, • multisystem trauma, • infection including bacterial and nonbacterial pneumonia, • inhaled toxic substances, • overdose of some drug, • acute pancreatitis.

  25. [ pathogenesis of ARDS] 1．direct injury of damage factor 2．indirect injury of inflammation medium

  26. 2. ventilatory disorders ▲edema, type Ⅱalveolar epithelial cells damage decreased lung volume airway obstruction obstructive ventilatory restrictive ventilatory disorders disorders ▲inflammation mediumbronchia spasmrespiratory failure • • 3．VA/Q mismatching ARDS [Mechanisms of respiratory failure] 1. diffusion disorders damage of alveolar-capillary membrane increased permeability diffusion disorders

  27. peripheral chemoreceptor ■PaO2↓＜60mmHgrespiratory center(+) respiratory movement↑ ＜30mmHg respiratory center (-) respiratory movement ↓ ■PaCO2↑ central chemoreceptor (+) respiratory movement↑ ＞80mmHg respiratory center (-) respiratory movement ↓ Effects of respiratory failure • Acid-base disturbances & disorders of electrolyte balance • Alteration of the respiratory system

  28. 3. Alteration of the respiratory system • ■ compensatory reaction • PaO2<60 mmHg，PaCO2 increase cardiovascular center(+) • increase in cardiac output : increase in stroke volume and heart rate • redistribution of blood flow • ■ injurious changes • PaO2< 40 mmHg，PaCO2> 80 mmHg cardiovascular center(-) • rate slow, decreased blood pressure • cardiac output decrease • pulmonary hypertension

  29. pulmonary vasoconstriction RBC↑ blood viscosity ↑ ■PaO2↓ Pulmonary vascular wall thickening and hardening blood resistance↑ Stenosis chronic pulmonary hypertension ■pulmonary arterial embolism, capillary damage afterload to right ventricle↑ ■Hypoxia, acidosis myocardial systolic and diastolic function(-) ■difficulty breathing Restricted diastolic co pulmonale ■co pulmonale

  30. 功能和代谢 4. Alteration of the nervous system (1) Hypoxia: the nervous system is very sensible to oxygen lack. < 40~50 mmHg, serious but reversible deterioration in cerebral function ( orientation, arithmetic tasks, memory) occurs, and restlessness and confusion are common. < 30 mmHg, loss of consciousness results. < 20 mmHg, irreversible damage of neural cells. (2) Hypercapnia: CO2 nacosis. a condition of confusion, tremors, convulsions, and possible coma that may occur if blood levels of carbon dioxide increase to 80 mm Hg or higher.

  31. [pulmonary encephalopathy] ■ cerebrovascular injury PaCO2↑, acidosisCerebral vasodilation Cerebral blood flow↑ hypoxia vascular endothelial damage extracellular brain edema edema on brain cell Vascular compression Increased cerebral anoxia Intracranial pressure↑ ■ Brain cell injury CSF pH↓＜7.25 EEG slow or stop GABA↑ pulmonary encephalopathy lysosomal membrane stability↓ lysosomal enzyme release nerve cell necrosis

  32. 4. Alteration of the renal function 5. Alteration of the digestive system

  33. Thanks for attention

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