Hypoxemic Respiratory Failure: Evidence, Indications, and Exclusions

ECMO is increasingly being used to manage severe ARDS with refractory hypoxemia and hypercapnia, and to facilitate lung-protective ventilation and minimize ventilator-associated lung injury. However, there is limited high-level evidence to support its use. Early randomized trials did not show a benefit, though these studies were hampered by high mortality rates, limited experience with ECMO, and antiquated technology. Since the advent of more advanced circuit components and increased experience with the use of this technology, survival rates with ECMO for ARDS have improved. There is only one randomized trial to date which used a more modern ECMO circuit. This trial, which has significant limitations, demonstrated a survival benefit from referral to a specialized center for consideration for ECMO. However, a prospective randomized trial comparing ECMO, using modern equipment, to standard-of-care mechanical ventilation has yet to be performed. There are no universally accepted guidelines for initiation of ECMO for ARDS, however suggested criteria include PaO(2) to FIO(2) ratio less than 80, uncompensated respiratory acidosis, and excessively high plateau airway pressures despite optimal ventilator management. Relative contraindications include prolonged ventilation at high airway pressures or high FIO(2), contraindications to anticoagulation, and concurrent severe, irreversible comorbidities.