Clinical evaluation of the Medtronic Maxima Plus membrane oxygenator

The purpose of this study was to clinically evaluate the degree of improvement, if any, in the oxygen transfer performance of the recently released Medtronic Maxima Plus membrane oxygenator. The outside diameter of the hollow fibres was reduced, increasing the membrane surface area from 2.0 m2 to 2.3 m2 without altering the polycarbonate housing. Maximum extrapolated oxygen transfer of the Maxima Plus (444 ml O2/minute) was increased 23.68% when compared to the Maxima (359 ml O2/minute). When expressed per metre squared of membrane surface area, the Maxima Plus had an increase of 13.5 ml O2/m2/minute (7.24%) over the Maxima. Pressure drop across the Maxima Plus was within 3.5 mmHg of the Maxima over the range of clinical blood flows indicating that the fibre bundle packing density was not significantly altered. Oxygen transfer consistency, expressed as a function of the standard deviation of oxygenator performance index values, was not significantly different for the two oxygenators. We concluded that the improvement in total oxygen transfer was due to an increase in membrane surface area as well as enhanced transfer efficiency per metre squared. We believe that the improved oxygen transfer performance was accomplished without impacting significantly upon the other attributes of the oxygenator (e.g., pressure drop, consistency, priming volume).