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PART IX. Diffuse Alveolar Disease. Chapter 27 Acute Respiratory Distress Syndrome. Figure 27-1. Adult respiratory distress syndrome. Anatomic Alterations of the Lungs. Interstitial and intra-alveolar edema and hemorrhage Alveolar consolidation Intra-alveolar hyaline membrane
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PART IX Diffuse Alveolar Disease
Chapter 27 Acute Respiratory Distress Syndrome Figure 27-1. Adult respiratory distress syndrome.
Anatomic Alterations of the Lungs • Interstitial and intra-alveolar edema and hemorrhage • Alveolar consolidation • Intra-alveolar hyaline membrane • Pulmonary surfactant deficiency or abnormality • Atelectasis
Other Names Used to Identify ARDS • Adult respiratory distress syndrome • Adult hyaline membrane disease • Capillary leak syndrome • Congestion atelectasis • Da Nang lung • Hemorrhagic pulmonary edema • Noncardiac pulmonary edema • Oxygen pneumonitis • Oxygen toxicity
Etiology: Multitude of Factors In alphabetical order, some of the better-known causes • Aspiration • Central nervous system disease • Cardiopulmonary bypass • Congestive heart failure • Disseminated intravascular coagulation • Drug overdose • Fat or air emboli • Infections • Inhalation of toxins and irritants
Etiology: Multitude of Factors In alphabetical order, some of the better-known causes • Inhalation of toxins and irritants • Immunologic reaction • Massive blood transfusions • Nonthoracic trauma • Oxygen toxicity • Pulmonary ischemia • Radiation-induced lung injury • Shock (hypovolemia) • Burns • Thoracic trauma
Overview of the Cardiopulmonary Clinical Manifestations Associated with ACUTE RESPIRATORY DISTRESS SYNDROME The following clinical manifestations result from the pathophysiologic mechanisms caused (or activated) by Atelectasis (see Figure 9-7), Alveolar Consolidation (see Figure 9-8), and Increased Alveolar-Capillary Membrane Thickness (see Figure 9-9)—the major anatomic alterations of the lungs associated with ARDS (see Figure 27-1).
Figure 9-9. Increased alveolar-capillary membrane thickness clinical scenario.
Clinical Data Obtained at the Patient’s Bedside Vital signs • Increased respiratory rate • Increased heart rate, cardiac output, blood pressure
Clinical Data Obtained at the Patient’s Bedside • Substernal/intercostal retractions • Cyanosis • Chest assessment findings • Dull percussion note • Bronchial breath sounds • Crackles
Figure 2-11. A short, dull, or flat percussion note is typically produced over areas of alveolar consolidation.
Figure 2-16. Auscultation of bronchial breath sounds over a consolidated lung unit.
Clinical Data Obtained from Laboratory Tests and Special Procedures
Pulmonary Function Study: Expiratory Maneuver Findings FVC FEVT FEF25%-75% FEF200-1200 N or N or N PEFRMVV FEF50% FEV1% N N or N N or
Pulmonary Function Study: Lung Volume and Capacity Findings VT RV FRC TLC N or VC IC ERV RV/TLC% N
Arterial Blood Gases Mild to Moderate ARDS • Acute alveolar hyperventilation with hypoxemia pH PaCO2 HCO3- PaO2 (Slightly)
Time and Progression of Disease Disease Onset Alveolar Hyperventilation 100 90 Point at which PaO2 declines enough to stimulate peripheral oxygen receptors 80 70 60 PaO2 PaO2 or PaCO2 50 40 30 PaCO2 20 10 0 Figure 4-2. PaO2 and PaCO2 trends during acute alveolar hyperventilation.
Arterial Blood Gases Severe ARDS • Acute chronic ventilatory failure with hypoxemia pH PaCO2 HCO3- PaO2 (Slightly)
Time and Progression of Disease Disease Onset Alveolar Hyperventilation Acute Ventilatory Failure 100 Point at which disease becomes severe and patient begins to become fatigued 90 Point at which PaO2 declines enough to stimulate peripheral oxygen receptors 80 70 PaCO2 Pa02 or PaC02 60 50 40 30 PaO2 20 10 0 Figure 4-7. PaO2 and PaCO2 trends during acute ventilatory failure.
Oxygenation Indices QS/QT DO2 VO2 C(a-v)O2 Normal Normal O2ER SvO2
Hemodynamic Indices (Severe ARDS) CVP RAP PAPCWP CO SV SVICI RVSWI LVSWI PVRSVR
Radiologic Findings Chest radiograph • Increased density • Ground-glass appearance
Figure 27-2. Chest X-ray of a patient with moderately severe ARDS.
General Management of ARDS Respiratory care treatment protocols • Oxygen therapy protocol • Hyperinflation therapy protocol • Mechanical ventilation protocol
General Management of ARDS Common ARDS mechanical ventilation strategy: • Low-tidal volumes and high respiratory rates • 4 to 8 mL/kg • Ventilatory rates as high as 35 breaths per minute • PEEP and/or CPAP—to offset atelectasis
General Management of ARDS The therapeutic goals of low-tidal volume ventilation • Decrease high transpulmonary pressure • Reduce overdistention of the lungs • Decrease barotrauma
General Management of ARDS Medications and procedures commonly prescribed by the physician • Antibiotics • Diuretics • Corticosteroids