Acute Respiratory Distress Syndrome Direct Lung Injury: Aspiration Inhaled toxins Pneumonia Near drowning Pulmonary contusion Indirect Lung Injury: Sepsis Pancreatitis Trauma Systemic inflammatory response syndrome Pathophysiology: Injury: Damage to alveolar epithelium and endothelium Release of inflammatory mediators (IL-1, IL-6, TNF-α) Inflammation: Neutrophil recruitment Cytokine release Increased capillary permeability Fluid leaks into interstitium Alveolar Damage: Hypoxemia Alveolar collapse Loss of surfactant Thickening of alveolar membrane Decreased gas exchange Pulmonary Edema: Fluid in alveoli and interstitium Decreased lung compliance V/Q mismatch Hypoxemia Clinical Features: Dyspnea Tachypnea Tachycardia Hypoxia Decreased lung compliance Bilateral pulmonary infiltrates on chest X-ray Treatment: Oxygen therapy Mechanical ventilation Positive end-expiratory pressure (PEEP) Diuretics Corticosteroids Antibiotics Complications: Acute respiratory failure Multiple organ dysfunction syndrome Death Prognosis: Mortality rate is high (30-40%) Long-term pulmonary fibrosis Impaired lung function **Belli Cilia** **Acute Hypoxemic Respiratory Failure** * PaO2 < 60 mmHg * Rapid, shallow breathing * Diffuse infiltrates on CXR * Significant hypoxemia * P/F ratio <300 **Complications:** * **Pulmonary Hypertension:** * RVH * RHF * Pulmonary edema * Hypoxemia * Vasoconstriction * Increased PVR * Increased afterload * **Pulmonary Embolism:** * Pleuritic chest pain * Tachycardia * Tachypnea * Hypoxia * Decreased breath sounds * Hypoxemia * V/Q mismatch * Increased alveolar dead space * Air leak syndromes * Pneumothorax * Pneumomediastinum * **Acute Respiratory Distress Syndrome (ARDS):** * Usually on ventilator > 2 days * Refractory hypoxemia * Bilateral infiltrates on CXR * P/F ratio < 200 * Reduced lung compliance * High plateau pressures **Treatment:** * **Oxygen Therapy:** * High-flow oxygen therapy * Non-invasive ventilation * Invasive mechanical ventilation * **Positive End-Expiratory Pressure (PEEP):** * Improves oxygenation * Recruits collapsed alveoli * Reduces alveolar collapse * **Diuretics:** * To reduce pulmonary edema * **Corticosteroids:** * To reduce inflammation * **Inhaled Nitric Oxide (INO):** * To improve oxygenation * To reduce pulmonary vascular resistance * **Extracorporeal Membrane Oxygenation (ECMO):** * For severe ARDS * Provides oxygenation and CO2 removal * **Prone Position:** * Improves oxygenation * Reduces V/Q mismatch