Emission of Micro-Bubbles in Bubble (BO) and Membrane-Oxygenators (MO): A Comparative Investigation

Summary

By means of Doppler-sonography, the emission of gas-bubbles in the arterial line was investigated in 10 in-vitro and 30 in-vivo experiments employing as oxygenators, two bubble (BOI + BOII), and two membrane oxygenators (MOI + MOII). It became evident that the occurrence of micro-bubbles was more frequent and greater in bubble oxygenators during extracorporeal circulation than in membrane oxygenators. Lowering blood levels and increasing gas-perfusion rates in the oxygenator reservoirs resulted in increased registration of micro-bubbles in the bubble oxygenators. When these parameters were similarly changed in the membrane oxygenators, there were no micro-bubbles produced, due to the absence of direct blood/gas contact. Observation of micro-bubbles in the arterial line of membrane oxygenators occurred during simultaneous injection of fluids into the venous line and during increased cardiotomy suction as was the case in MOII, meaning bubbles escaped through the membrane oxygenator. Just as in MOII, the membrane in MOI is not a perfect gas-filter. Prevention of gas-emboli could be achieved through insertion of a de-foamer and additional filters. By keeping blood volume at safe levels as prescribed by the producer, we observed no micro-bubbles in the arterial-line during this investigation.