<prompt> Which of the following defines ARDS ae?Pao2Fio2 300Acute onsetPCWP 18 mm HgBilateral alveolar infiltrates  <response>: Ans. c. PCWP18mmHgACUTE RESPIRATORY DISTRESS SYNDROMERespiratory failure with refractory hypoxemia, lung compliance, and non-cardiogenic pulmonary edema with a PaO2 FiO2 ratio300.Pathogenesis is thought to be dependent on endothelial injury. Common triggers include sepsis, pneumonia, aspiration, multiple blood transfusions, inhaledingested toxins, and trauma. Overall mortality is 30-40.HISTORYPEPresents with acute-onset 12-48 hours tachypnea, dyspnea, and tachycardia - fever, cyanosis, labored breathing, diffuse high-pitched rales, and hypoxemia in the setting of one of the systemic inflammatory causes or exposure.Additional Findings are as FollowsPhase 1 acute injury: Normal physical examination; possible respiratory alkalosis.Phase 2 6-48 hours: Hyperventilation, hypocapnia, widening A-a gradient.Phase 3: Acute respiratory failure, tachypnea, dyspnea, lung compliance, scattered rales, and diffuse chest opacity on CXR see Fig. 1.AP CXR showing a diffuse alveolar filling pattern deg to ARDSPhase 4: Severe hypoxemia unresponsive to therapy; intrapulmonary shunting; metabolic and respiratory acidosis.DIAGNOSISThe criteria for ARDS diagnosis according to the Berlin definition are as follows:Acute onset 1week of respiratory distress.A PaO2 FiO2 ratio300with PEEPCPAP5cmH2O,Bilateral pulmonary infiltrates on CXR.Respiratory failure not completely explained by heart failure.TREATMENTTreat the underlying disease and maintain adequate perfusion to prevent end-organ damage.Mechanical ventilation with low tidal volumes 4-6 cckg of ideal body weight to minimize ventilator-induced lung injury,Use PEEP to recruit collapsed alveoli, and titrate PEEP and Fi02 to achieve adequate oxygenation.Goal oxygenation is PaO,55mmHgorSaO2 88. 