Inclusion Criteria:  Age ≥ 18 years Endotracheal mechanical ventilation for ≤ 5 days Early moderate-severe ARDS (Berlin Definition) - all of the following conditions for ≤ 48 hours i. PaO2/FiO2 ≤200 with PEEP > 5 cmH2O ii. bilateral opacities not fully explained by effusions, lobar/lung collapse, or nodules iii. respiratory failure not fully explained by cardiac failure or fluid overload iv. within one week of a known insult of new or worsening respiratory symptoms  ARDS severity criterion - either 1 of:  PaO2/FiO2 ≤ 150 mm Hg, on PEEP ≥ 10 cm H2O and FiO2 ≥ 0.5  Exclusion Criteria:  Currently receiving any form of ECMO (e.g., venovenous, venoarterial, or hybrid configuration) Chronic hypercapnic respiratory failure defined as PaCO2 > 60 mmHg in the outpatient setting Home mechanical ventilation (non-invasive ventilation or via tracheotomy), not CPAP Actual body weight exceeding 1 kg per centimeter of height Severe hypoxemia with PaO2/FiO2 < 80 mmHg Expected mechanical ventilation duration < 48 hours Treating team is in the process of moving to a palliative mode of care Moribund patient not expected to survive 24 hours despite ongoing life-sustaining therapies Confirmed diffuse alveolar hemorrhage from vasculitis Contraindications to limited anticoagulation (e.g., active GI bleeding, bleeding diathesis) Pregnancy - due to unknown effects of PaCO2 changes on placental blood flow