Advanced Mechanical Ventilation - FINAL

Advanced Mechanical Ventilation - FINAL - John J. Marini...

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Unformatted text preview: John J. Marini John J. Marini Alain F. Broccard Alain F. Broccard University of Minnesota University of Minnesota Regions Hospital Regions Hospital Minneapolis / St. Paul Minneapolis / St. Paul USA USA Advanced Mechanical Advanced Mechanical Ventilation Ventilation Advanced Mechanical Ventilation Outline Advanced Mechanical Ventilation Outline Consequences of Elevated Alveolar Pressure Implications of Heterogeneous Lung Unit Inflation Adjuncts to Ventilation Prone Positioning Recruitment Maneuvers Difficult Management Problems Acute Lung Injury Severe Airflow Obstruction An Approach to Withdrawing Ventilator Support Advanced Modes for Implementing Ventilation Case Scenarios Consequences of Elevated Alveolar Pressure--1 Consequences of Elevated Alveolar Pressure--1 Mechanical ventilation expands the lungs and chest wall by pressurizing the airway during inflation. The stretched lungs and chest wall develop recoil tension that drives expiration. Positive pressure developed in the pleural space may have adverse effects on venous return, cardiac output and dead space creation. Stretching the lung refreshes the alveolar gas, but excessive stretch subjects the tissue to tensile stresses which may exceed the structural tolerance limits of this delicate membrane. Disrupted alveolar membranes allow gas to seep into the interstitial compartment, where it collects, and migrates toward regions with lower tissue pressures. Interstitial, mediastinal, and subcutaneous emphysema are frequently the consequences. Less commonly, pneumoperitoneum, pneumothorax, and tension cysts may form. Rarely, a communication between the high pressure gas pocket and the pulmonary veins generates systemic gas emboli. Partitioning of Alveolar Pressure is a Function of Lung Partitioning of Alveolar Pressure is a Function of Lung and Chest Wall Compliances and Chest Wall Compliances Lungs are smaller and pleural pressures are higher when the chest wall is stiff. Hemodynamic Effects of Lung Inflation Hemodynamic Effects of Lung Inflation Lung inflation by positive pressure causes Increased pleural pressure and impeded venous return Increased pulmonary vascular resistance Compression of the inferior vena cava Retardation of heart rate increases These effects are much less obvious in the presence of Adequate circulating volume Adequate vascular tone Spontaneous breathing efforts Preserved adrenergic responsiveness Hemodynamic Effects of Lung Inflation Hemodynamic Effects of Lung Inflation With Low Lung Compliance, High Levels of PEEP are Generally Well Tolerated. Effect of lung expansion on pulmonary vasculature . Capillaries that are embedded in the alveolar walls undergo compression even as interstitial vessels dilate. The net result is usually an increase in pulmonary vascular resistance, unless recruitment of collapsed units occurs. Conflicting Actions of Higher Airway Pressure Conflicting Actions of Higher Airway Pressure Lung Unit Recruitment and Maintenance of Aerated Volume...
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This note was uploaded on 12/27/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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Advanced Mechanical Ventilation - FINAL - John J. Marini...

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