3 Respirationexternal respiration（pulmonary ventilation and gas exchange in lung）transport of gasinternal respiration
4 respiratory insufficiency Respiratory failureconcept and classificationrespiratory insufficiencyThe 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.
5 2. respiratory failure normal reference values ： Respiratory failure is a syndrome in which the respiratorysystem fails in one or both of its gas exchange functions:oxygenation and carbon dioxide elimination.In practice, respiratory failure is defined as a PaO2 valueof 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
6 3．classification （1）according to PaCO2 ■ hypoxemic (Group Ⅰ) respiratory failurea PaO2 of less than 60 mm Hg with a normal or low PaCO2.Cause of: Edema, Vascular disease, Chest Wall.■ hypercapnic (Group Ⅱ ) respiratory failurea PaO2 low 60 mm Hg and PaCO2 of more than 50 mm Hg.Cause of: Airway obstruction, Neuromuscular disease.
7 （2）according to pathogenic mechanism ■ ventilatory disorders■ gas exchange disorders（3）according to primary site■ central respiratory failure■ peripheral respiratory failure（4）according to duration■ acute respiratory failure■ chronic respiratory failure
8 ventilatory disorders gas exchange disorders ventilation-perfusion etiology and pathogenesis【classification of respiration failure mechanism】ventilatory disordersgas exchange disordersrespiratory failureobstructive ventilatorydisordersrestrictive ventilatorydiffusion disordersventilation-perfusionmismatching
9 Ⅰ. ventilatory disorders 1. restrictive ventilatory disordersRestrictive hypoventilation is caused by the diseases that affect the distensibility of the alveolar.
11 Respiratory movement ↓ alveolar distensibility ▲ Disorders of the respiratory musclesRespiratory movement ↓Depression of CNSdamage of CNSdrug overdoseRespiratorymovementdisorderneuro-muscular disordersdecreased strength, myasthenia gravishypoxia, acidosisalveolar distensibilityRestrictiveventilatorydisordersrespiratory failure
12 deformity of thorax , fracture of several ribs, tension ▲ decreased lung compliance● decrease of pulmonary surfactants and increase ofsurface tension force● diffuse interstitial fibrosis▲ decreased thoracic compliance of lungdeformity of thorax , fracture of several ribs, tensionpneumothorax, thickened constrictive pleural layer.
13 2. obstructive ventilatory disorders 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.■ etiologyasthma, emphysema, chronic bronchitis, and bronchiectasis.
14 three depression sign 1） central airway obstruction defined as airway obstruction between the glottis and the carinathree depression sign■Obstruction is located in theairway outside the thorax：inspiratory dysnea+■Obstruction is located in theairway inside the thorax：expiratory dysneaexpire inspire
15 equal pressure point (EPP) 2） peripheral airway obstructionsmaller 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 ,bingdingeffect of attachments of the surroundinglung parenchyma.equal pressure point (EPP)In forced expiration, the point where intrapleural pressure and alveolar pressure are equal.
16 Peripheral airway obstruction may be caused by: specific chemical mediators (such as histamine, leukotrienes, prostaglandins ), other substances released during inflammatory and allergic responses.forced expirationEPP 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.
17 3. The alteration of blood gas 1）Low PaO2 ： PaO2 < 60mmHg2）PaCO2 change：A. hypoventilation：high PaCO2.R=40/50 mmHg=0.8；B. part hypoventilation: Low PaO2 and normal or low PaCO2.
18 Ⅱ. gas-exchanging dysfunction 1. diffusion disordersThe 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.
19 1） etiology of diffusion disorders ■ reduction of diffusion membrane areaAbnormalities of diffusion may not cause arterial hypoxia inpersons at rest unless they are extremely severe.(total: 80 mm2; at rest: 30~40 mm2)Causes: emphysema, pneumonia, lobectomy■ increase of diffusion membrane thicknessedema, fibrosis, capillary vessel dilatation■ decreased time of blood contacts with alveolar
20 2. ventilation/perfusion imbalance The dysfunction of gas exchange can arise secondary to ventilation /perfusion mismatching.VA Q VA/ QTop L/min L/minMiddle L/min L/minBottom L/min L/min
21 · · · 1) type and cause of ventilation-perfusion-mismatching (1) decreased ratio of VA/Qunderventilated in relation to their perfusionasthma, chronic bronchitis, obstructive emphysema, fibrosis, edemaVA/ Q↓ part alveolar ventilatory ↓functional shunt↑>30% respiratory failure
22 · · poor perfusion in relation to their ventilation with air (2) increased ratio of VA/Qpoor perfusion in relation to their ventilation with airpulmonary artery embolization, DIC in lung, vessels contract, pulmonary arteritis,dead space like ventilation VA/Q↑ poor perfusion↓respiratory failure
23 Pulmonary A-V shunt open↑ 3）increased of anatomical shuntRight-to-left shunts or anatomic shunt▲ increased of anatomical shuntbronchiectasisanatomic shunt↑Pulmonary A-V shunt open↑true shunt↑Respiratoryfailurepulmonary consolidation,Atelectasisanatomical-like shunt▲ increased of结
24 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.
25 [etiology] shock from any cause, multisystem trauma, infection including bacterial and nonbacterial pneumonia,inhaled toxic substances,overdose of some drug,acute pancreatitis.
26 [ pathogenesis of ARDS] 1．direct injury of damage factor2．indirect injury of inflammation medium
27 [Mechanisms of respiratory failure] ARDS[Mechanisms of respiratory failure]1. diffusion disordersdamage of alveolar-capillary membrane increased permeabilitydiffusion disorders2. ventilatory disorders▲edema, type Ⅱalveolar epithelial cells damage decreased lung volumeairway obstruction obstructive ventilatory restrictive ventilatorydisorders disorders▲inflammation medium bronchia spasm respiratory failure3．VA/Q mismatching• •
28 Effects of respiratory failure Acid-base disturbances & disorders of electrolyte balanceAlteration of the respiratory systemperipheral chemoreceptor■ PaO2↓＜60mmHg respiratory center(+) respiratory movement↑＜30mmHg respiratory center (-) respiratory movement ↓■ PaCO2↑ central chemoreceptor (+) respiratory movement↑＞80mmHg respiratory center (-) respiratory movement ↓
29 3. Alteration of the respiratory system ■ compensatory reactionPaO2<60 mmHg，PaCO2 increase cardiovascular center(+)increase in cardiac output : increase in stroke volume and heart rateredistribution of blood flow■ injurious changesPaO2< 40 mmHg，PaCO2> 80 mmHg cardiovascular center(-)rate slow, decreased blood pressurecardiac output decreasepulmonary hypertension
30 blood resistance↑ co pulmonale ■ co pulmonale ■PaO2↓blood resistance↑pulmonary vasoconstrictionRBC↑ blood viscosity ↑StenosisPulmonary vascular wallthickening and hardeningco pulmonaleafterload to right ventricle↑chronic pulmonary hypertension■pulmonary arterial embolism, capillary damage■ Hypoxia, acidosis myocardial systolicand diastolic function(-)■difficulty breathing Restricted diastolic
31 4. Alteration of the nervous system 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 andconfusion 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 thatmay occur if blood levels of carbon dioxide increase to 80 mm Hg or higher.