Snapshot A 46-year-old woman is admitted to the medical intensive care unit with severe pancreatitis. During the first 72 hours of admission, she becomes confused with increased work of breathing. Her oxygen saturation is 82% and physical exam is remarkable for tachypnea, nasal flaring, and abdominal contractions. She is placed on mechanical ventilation. A chest radiograph demonstrates bilateral infiltrates with no evidence of cardiomegaly or pleural effusions. Introduction Definition a clinical syndrome characterized by inflammatory lung injury leading to acute hypoxemia and bilateral radiographic infiltrates Berlin Definition of ARDS acute onset (within 1 week of clinical insult or worsening respiratory status) bilateral infiltrates (without an alternative explanation) respiratory failure not caused by cardiac causes or volume overload hypoxemia ARDS severity mild PaO2/FiO2 is 200-300 moderate PaO2/FiO2 is 100-200 severe PaO2/FiO2 is < 100 Etiology Pneumonia (most common risk factor) Aspiration Pulmonary contusion Acute pancreatitis Sepsis Pathogenesis injury and inflammation to the alveoli increases pulmonary capillary permeability phases exudative immune-mediated destruction of the epithelial-interstitial-endothelial barrier allows fluid into the interstitium and airspace proliferative recovery of the destroyed barrier fibrotic impaired removal of alveolar collagen that was produced during the early injury process limits functional recovery impaired gas exchange Presentation Symptoms dyspnea Physical exam tachypnea tachycardia diffuse crackles Imaging Chest radiography indication initial imaging study in the workup of ARDS Differential Diffuse alveolar hemorrhage differentiating factor in addition to acute respiratory failure, patients also have an unexplained drop in their hemoglobin concentration Vaping-associated lung disease ground-glass opacities on imaging that can progress to ARDS DIAGNOSIS Making the diagnosis based on Berlin definition Treatment Approach to treatment the goal is to maintain gas exchange while avoiding ventilator-induced lung injury Interventional mechanical ventilation indication to maintain adequate gas exchange while minimizing lung injury low tidal volume low plateau pressures titrating up positive end-expiratory pressure (PEEP) PEEP protects against atelectrauma settings initial tidal volume to 8 mL/kg and reduce gradually to 6 mL/kg (low tidal volumes) want to achieve an inspiratory plateau airway pressure ≤ 30 cm H2O titrate PEEP to prevent tidal alveolar collapse initial respiratory rate to approximate baseline minute ventilation (≤ 35/min) oxygenation goal is a PaO2 of 55-80 mmHg pH goal is 7.30-7.45 Prognosis Severe ARDS has the worst mortality (45%) compared to mild and moderate