Oxygen transfer performance of the Sorin Monolyth membrane oxygenator was evaluated. Similar to previous oxygen transfer performance studies conducted at this institution, our purpose was sixfold: (1) to construct an oxygen transfer slope (OTS); (2) to find the maximum extrapolated oxygen transfer; (3) to calculate the oxygenator performance index (OPI); (4) to generate a shunt fraction line; (5) to determine the percentage of predicted shunt (POPS); and (6) to compare the Monolyth's performance to several previously studied membrane oxygenators. From the OTS, the maximum extrapolated oxygen transfer was 346.4 ml O2/min. This absolute value was the lowest of the four oxygenators compared. When maximum oxygen transfer was compared relative to membrane surface area, the Monolyth ranked third (157.5 ml O2/min). The Monolyth produced a relatively narrow range for the OPI (81.64-130.47%) and had the lowest standard deviation (SD) in this group. The Monolyth exhibited higher shunt fractions over the range of clinical blood flows when compared to our three previously studied oxygenators. The range of POPS values (71.65-128.77%) was relatively narrow and the SD was the lowest of the four. We concluded from our evaluation that the Monolyth had relatively low top end oxygen transfer capabilities, but provided very consistent and predictable oxygen transfer performance.

We believe we have fulfilled the five objectives outlined in the introductory section to this text. Unquestionably, the clinical perfusionist will be confronted with a set of conditions that do not match the very specific values proposed for our in vitro performance testing. The in vitro results for a particular brand of oxygenator can serve as a 'performance baseline', predicting oxygen transfer performance under standard conditions. It is encumbant upon the clinical perfusionist to assess the impact that each variable (i.e. Hb, blood flow and SvO2) will have on the overall oxygen transfer performance. Table 5 illustrates how increases or decreases in each of these three variables can influence the resulting VO2/minute. The clinical perfusionist must manipulate these variables in order to satisfy the oxygen transfer demand created by the patient on CPB. In order for the in vitro performance testing to be helpful in the clinical environment, the perfusionist must: (1) be familiar with the results and the conditions under which they were achieved; and (2) be able to assess and interpret how their current set of conditions on cardiopulmonary bypass will impact on the oxygenator's performance. Example Brand Y membrane oxygenator is being used clinically on a patient weighing 115 kg and consuming 320 ml O2/minute. According to Table 4, this VO2/minute exceeds the 277.2 ml O2/minute achieved during its in vitro performance test.(ABSTRACT TRUNCATED AT 250 WORDS)

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).

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