Assessing Lung Inhomogeneity During Ventilation for Acute Hypoxemic Respiratory Failure

Inclusion Criteria: * Acute (≤7 days) hypoxemia with PaO2:FiO2 ratio less than or equal to 200 mm Hg * Oral endotracheal intubation and mechanical ventilation * Bilateral airspace opacities on chest radiograph or CT Exclusion Criteria: * Contraindication to EIT electrode placement (burns, chest wall bandaging limiting electrode placement) * Contraindication to esophageal catheter placement (recent upper GI surgery, actively bleeding esophageal varices) * Respiratory failure predominantly due to cardiogenic cause or fluid overload * Ongoing hemodynamic instability (requiring 2 vasopressor agents by continuous infusion AND rising vasopressor infusion rate requirements in the previous 8 hours) * Ongoing ventilatory instability (P/F \< 70 mm Hg, pH \< 7.2; ventilator driving pressures, PEEP, or FiO2 increasing by more than 25% in previous 30 minutes) * Intracranial hypertension (suspected or diagnosed by medical team) * Known or suspected pneumothorax recognized within previous 72 hours * Bronchopleural fistula * Bridge to lung transplant * Recent lung transplantation (within previous 6 weeks) * Attending physician deems the transient application of high airway pressures (\>40 cm H2O) to be unsafe