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.

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During cardiopulmonary bypass (CPB), the perfusionist must be able to differentiate between: (1) a normal oxygenator with oxygen transfer reserve; (2) a normal oxygenator without O2 transfer reserve; and (3) a failing or suboptimal oxygenator. The purpose of this paper is to report on the use of the oxygen transfer slope, as well as other evaluation techniques previously described, which aided in the differential diagnosis of suboptimal oxygenator performance. We were able to determine the presence and extent of the dysfunction, follow the progression over time, and assess the effectiveness of our intervention. As a direct result of our ability to carefully monitor the oxygenator, replacement was not necessary despite severe dysfunction.

Sarns/3M Health Care has recently introduced the CDI 500 Blood Parameter Monitoring System. In addition to parameters previously available, this system now offers continuous monitoring of the patient’s oxygen consumption (VO2/min) and potassium concentration ([K+]). The purpose of this study was: (1) to compare the [K+] from the CDI 500 with the [K+] derived from our hospital’s laboratory; and (2) to compare the VO2/min from the CDI 500 with the results obtained utilizing the “gold-standard” Fick equation. The mean absolute difference in [K+] was 0.10 mEq/L with a mean percentage error of only 3.93%. The mean absolute difference in VO2/min was 18.78 ml O2/min, with a mean percentage error of 11.63%. We concluded that the [K+] correlated well and that 9.13% of the oxygen consumption percentage error was attributable to the exclusion of dissolved oxygen in the calculation used by the CDI 500, with the remaining 2.5% attributable to differences in technology. We recommended that future upgrades to the CDI 500 should include dissolved O2 when measuring oxygen consumption and consideration should be given to increasing the operating range for [K+].

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