OBJECTIVE To determine whether modifications of the original design of a double-lumen, venovenous, extracorporeal membrane oxygenation (ECMO) catheter would reduce recirculation and improve oxygenation during venovenous ECMO. METHODS Prospective, interventional study. METHODS The animal research laboratory at The Children's National Medical Center. METHODS Six newborn lambs, 1 to 7 days old and weighing 4.7 +/- 0.9 kg. METHODS Animals were anesthetized, intubated and ventilated. The ductus arteriosus was ligated. Femoral artery and vein, cephalic jugular vein, and pulmonary artery catheters were placed. After systemic heparinization, the test catheter (with venous drainage holes moved away from the arterial return holes) was placed in the right internal jugular vein and advanced into the right atrium. The animal was placed on ECMO and stabilized, with the ventilator settings decreased to a peak inspiratory pressure of 15 cm H2O, peak positive end-expiratory pressure of 5 cm H2O, respiratory rate of 15 breaths/min, and an FIO2 of 0.21. ECMO flows were increased in 100-mL increments from 200 to 600 mL/min, with measurements taken 15 mins after each change. The test catheter was removed, the double-lumen, venovenous ECMO catheter was placed, and the studies were repeated. RESULTS Heart rate, mean arterial pressure, PaO2, jugular cerebral oxygen saturation, pulmonary artery oxygen saturation, mixed venous oxygen saturation, and postmembrane circuit pressures were measured at each study period. The test catheter improved oxygenation significantly, with higher systemic PaO2, higher pulmonary artery and cerebral oxygen saturations, and lower mixed venous oxygen saturations (indicating less recirculation). With the test catheter, PaO2 levels ranged from 62 +/- 6 torr (8.3 +/- 0.8 kPa) to 112 +/- 12 torr (14.9 +/- 1.6 kPa), compared with 46 +/- 4 torr (6.1 +/- 0.5 kPa) to 59 +/- 2 torr (7.9 +/- 0.3 kPa) for the double-lumen, venovenous ECMO catheter (p < or = .001). These findings indicate that at all flow rates studied, less recirculation occurred with the test catheter than with the double-lumen, venovenous ECMO catheter. CONCLUSIONS These findings indicate that the redesign of the double-lumen, venovenous ECMO catheter, as outlined in this study, resulted in a significant reduction of recirculation, thereby resulting in a significant improvement in oxygenation while on venovenous ECMO. This newly designed catheter makes venovenous ECMO more effective, and represents a design that could be used for pediatric and/or adult ECMO.