Studies of Extracorporeal Membrane Oxygenation (ECMO) for Neonatal Acute Respiratory Failure

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Conventional ECMO circuits with a roller pump are not always free from serious mechanical problems like venous collapse, air embolism, burst of the arterial line. A new, safer, and more practical ECMO circuit with an automatic blood pump was developed. Our neonatal ECMO circuit primed 65 ml consisted of blood pumps with 4 mm ball valves and a membrane oxygenator of 0.5 sq.m. Our pediatric ECMO circuit primed 120 ml with 6 mm valves and a membrane oxygenator of 0.8 sq.m. The pump could change output automatically in response to its filling and thereby did not produce excessive negative pressure.Our ECMO circuits had been extensively tested on a mock circulation system and used on dogs. No mechanical problem had been encountered in continuous driving on the mock circulation system for 21 days. Bypass flow changed automatically in response to venous return, but remained constant against changes in arterial pressure.Effect of ECMO using our automatic blood pumps on hemodynamics was studied on 50 dogs. During VA-ECMO mean pulmonary arterial pressure and right ventricular pressure decreased. When the flow increased more than 50 ml/kg/min, the aortic systolic pressure tended to decrease more significantly than the systolic left ventricular pressure. The endodiastric pressure in both right and left ventricles elevated at high bypass flow. These findings indicated that VA-ECMO of high frow caused ventricular strain.In conclusion, our automatic ECMO circuit is a safe and useful device treating small infants with acute respiratory failure but VA-ECMO flow should be kept as little as possible because of possible ill effects on the heart.