Acute Respiratory Distress Syndrome: Pathogenesis and clinical findings
Note: Acute respiratory distress syndrome is a clinical syndrome involving acute lung injury. It results in severe hypoxemia and bilateral airspace disease in the absence of elevated left-heart pressures.
Direct Lung Injury Causes include pneumonia and pulmonary sepsis (community-acquired, hospital-acquired, aspiration, viral), drowning, and chemical pneumonitis from aspiration or direct inhalational injury
v), Lung Tissue Inflammation
Exudative: Neutrophils migrate into the alveoli in response to inflammatory stimulus
Note: While the three phases of ARDS take place in sequence, all areas of the lung may not be in the same phase at the same time. For this reason, the processes can be thought of as overlapping.
Proliferative: Body attempts to heal damage. If it is not successful, the tissue transitions to the fibrotic phase
Neutrophil-containing ♦ pulmonary exudate interferes with surfactant function
Neutrophil infiltration and proinflammatory cytokines lead to tissue edema, dysfunction and subsequent destruction of pulmonary epithelium
Abbreviations: Pa02: Partial pressure of oxygen in arterial blood 5p02: Peripheral oxygen saturation. CXR: Chest radiograph.
Residual debris in alveoli are cleared by phagocytic cells
Restoration of alveolar epithelial cells.
Authors: David Olmstead Reviewers: Midas (Kening) Kang Usama Malik Kevin Solverson* * MD at time of publication
Indirect Lung Injury Causes include sepsis with a non-pulmonarysource, trauma, severe burns, transfusion-related acute lung injury (TRALI) and pancreatitis
Alveoli collapse in absence of working surfactant
Damaged epithelium impairs gas exchange
Pulmonary capillaries do not adequately absorb fluid
The body’s attempts to heal lung tissue result in deposition of hyaline membranes in the alveoli
Pulmonary —r÷ Edema
Impaired Gas Diffusion
1` useful surface area for gas exchange
Functional epithelium is able to absorb fluid back into circulation
4. Pa02, 4,Sp02
Bilateral Opacity on CXR
4. Pa02, J,SpO2
4, 02 Requirements
Clearing of CXR
Depression, Anxiety, PTSD
Fibrotic: Inadequate results in long-term damage Impaired healing pulmonary (rare) Function After Prolonged Illness Fibroblast activity leads to deposition of collagen in alveoli and alveolar capillaries Pulmonary Fibrosis Neuromuscular Cough/Dyspnea Weakness Nail Clubbing Pulmonary Hypertension Chronic Respiratory Fatigue Dysfunction