In the earlier NHLBI trial, ECMO was implemented with a veno-arterial shunt which approximated 90 percent of the baseline cardiac output. Ventilation of the lungs was continued with reduced function of inspiration oxygen. Thus, the lungs were deprived of the principle source of blood supply while continuously exposed to potentially injurious ventilatory pressures and gas composition. The present patient trial used a new form of therapy developed by Dr. Gattinoni and co-workers in Milan, Italy with the collaboration of Dr. Kolobow at the National Institutes of Health in Bethesda. The authors reported a 77 percent survival rate for the new therapy. In Step 1 of the new therapy, the patient was initially ventilated with pressure-controlled, inverted ratio ventilation. If the patient did not improve, Step 2 using extracorporeal perfusion was performed with a veno-venous shunt in contrast to a veno-arterial shunt. The veno-venous shunt preserved pulmonary blood flow whereas the veno-arterial shunt diminished it. Step 3 was reserved for those patients who did not meet the therapeutic criteria of Step 2. They underwent low frequency positive-pressure ventilation and extracorporeal CO2 removal involving veno-venous bypass via the internal jugular and femoral or bilateral saphenous veins.