Stress Index to Individualize Mechanical Ventilation in ARDS

Inclusion Criteria: * Admitted to the Intensive Care Unit * Receiving invasive mechanical ventilation via endotracheal or tracheostomy tube * Presence of ARDS by Berlin Criteria (acute onset bilateral pulmonary infiltrates incompletely explained by left heart failure together with a PaO2/FiO2 of \<300 or SpO2/FiO2 \<315) Exclusion Criteria: * Inability to obtain surrogate consent * Presence of specified comorbidities: 1. pregnancy 2. pre-existing severe chronic obstructive pulmonary disease, defined as FEV1 documented \< 1L or baseline hypercapnia 3. cerebral edema 4. known intra-cranial abnormality 5. acute coronary syndrome * Endotracheal or tracheostomy cuff leak * Chest tube with persistent air leak * Severe hemodynamic instability (defined as attending judgment that the patient is unable to safely tolerate ventilator manipulations) * Presence of spontaneous respiratory activity as evidenced by examination of the ventilator waveform tracing * Intrinsic PEEP of \> 5 cmH2O * Assessment of study staff or patient's attending physician that the patient would not be a good study participant