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Acute respiratory distress syndrome

Acute respiratory distress syndrome

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Acute respiratory distress syndrome

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  1. Acute respiratory distress syndrome Prof.M.K.Arora Dr.Lenin Dr.Prabhu www.anaesthesia.co.inanaesthesia.co.in@gmail.com

  2. History • Described by Ashbaugh et al in 1967 Acute respiratory distress in adults Ashbaugh DG et al .Lancet 1967 • “Adult respiratory distress syndrome” Term was coined by Petty TL, Ashbaugh DG. Chest 1971

  3. Other names • Adult hyaline-membrane disease • Adult respiratory insufficiency syndrome • High output respiratory failure • Congestive atelectasis • Hemorrhagic lung syndrome • Da Nang lung • Stiff-lung syndrome • Shock lung • White lung Taylor RW et al Res Medica 1983;1:17-21.

  4. Definition • Lung injury score • Modified lung injury score • NAECC Definition

  5. Definition • Three part expanded definition • Part 1- acute or chronic on course • Part 2- lung injury score • Part 3- associated risk factors such as sepsis, pneumonia, aspiration or major trauma Murray JF, Matthay MA 1988

  6. Lung injury score • Chest radiograph • Hypoxemia score • PEEP score • Respiratory compliance score

  7. CXR No consolidation ..0 Confined to 1 quadrant …………1 2 quadrant ……….2 3 quadrant ……….3 4 quadrant ……….4 PaO2/FiO2 >300……..0 225-299 …1 175-224 …2 100-174 …3 <100……..4 Lung injury score…

  8. PEEP (when mechanically ventilated) <5 cm H2O……..0 6-8 cm H2O ……1 9-11 cm H2O …..2 12-14 cm H2O ....3 >15 cm H2O …...4 Compliance (when available) >80 ml/ cm H2O …..0 60-79 ml/ cm H2O ...1 40-59 ml/ cm H2O …2 20-39 ml/ cm H2O …3 <19 ml/ cm H2O …...4 Lung injury score…

  9. Lung injury score… Add the sum of each component and divide by the number of components used 0- No lung injury 0.1-2.5 – Mild to moderate lung injury >2.5 – Severe lung injury (ARDS)

  10. Modified lung injury score • PaO2/FiO2 <174 • Bilateral infiltrates on chest x-ray

  11. NAECC Definition 1994,1998 • Onset- acute and persistent • Oxygenation criteria PaO2/FiO2≤ 300 for ALI PaO2/FiO2≤ 200 for ARDS • Exclusion criteria- PAOP ≥ 18 mmHg Clinical evidence of left atrial hypertension • Radiographic criteria- bilateral opacities consistent with pulmonary edema Bernard GR et al 1994

  12. Incidence

  13. Common Aspiration pneumonia Pneumonia Less common Inhalational injury Pulmonary contusion Fat emboli Near drowing Reperfusion injury Asso. clinical disorders-direct

  14. Common Sepsis Severe trauma Multiple fractures Multiple blood transfusion Less common Acute pancreatitis Cardiopulmonary bypass DIC Burns Head injury Asso. clinical disorders-indirect

  15. Risk factors predictive of mortality • Liver dysfunction/ cirrhosis • Sepsis • Non pulmonary organ dysfunction • Age > than 65 • Organ transplantation, HIV, active malignancy, chronic alcoholism, mechanim of lung injury

  16. Pathogenesis Lung injury • The pulmonary response to a broad range of injuries occuring either -directly to the lungs -or as the consequence of injury or inflammation at other sites in the body

  17. Acute Exudative Phase Exudative phase • Commencing within 24 hrs • 1-7 days • Diffuse alveolar damage • Diffuse Microvascular injury • Neutrophil infiltration • Edematous alveolar wall • Hyaline membrane

  18. Acute Exudative Phase • Basement membrane disruption • Type I pneumocytes destroyed • Type II pneumocytes preserved • Surfactant deficiency • inhibited by fibrin • decreased type II production • Microatelectasis/alveolar collapse • Self limited or progresses

  19. Proliferative phase • For 3-10 days • Type II pneumocyte • proliferate • differentiate into Type I cells • reline alveolar walls • Fibroblast proliferation • interstitial/alveolar fibrosis

  20. Fibrotic Phase • 1-2 weeks • Characterized by: • local fibrosis • vascular obliteration • Repair process: • resolution vs fibrosis

  21. Pathophysiology • Interstitial / alveolar edema • Severe hypoxemia • due to intra-pulmonary shunt • High ventilatory demands • high metabolic state • increased VD/VT • decreased lung compliance • Pulmonary HTN

  22. Clinical features- CHF & ARDS • Anxiety, dyspnea, tachypnea • Reduced lung volumes • Decreased lung compliance • ABG- respiratory alkalosis, hypoxemia • CXR

  23. Favour of ARDS • ARDS risk factors • PCWP • BALF is proteinaceous and inflammatory • Pathological findings

  24. Diagnosis • Based on clinical criteria • no diagnostic tests • Confirmatory tests: • PA catheter • PAWP = normal/reduced • [bronchial secretion protein]:[serum protein] • ratio > 70% - 80% • CT scan-heterogenous pattern with a predominance of infiltration in the dependent region

  25. Differential Diagnosis • Cardiogenic pulmonary edema • Bronchopneumonia • Hypersensitivity pneumonitis • Pulmonary hemorrhage • Acute interstitial pneumonia (Hamman-Rich Syndrome) www.anaesthesia.co.inanaesthesia.co.in@gmail.com