An Experimental Evaluation of the Capiox 1.6 and 5.4M<sup>2</sup> Membrane Oxygenators for Air Removal Efficiency in the Conventional and Inverted Positions

The purpose of this study was to evaluate the oxygen transfer performance of two membrane oxygenators: Bentley Univox and the Bard HF 5000. This evaluation was based on the comparison between: (1) the oxygen transfer slope; (2) the gas phase-arterial oxygen gradients; (3) the degree of blood shunting; (4) the maximum oxygen transfer; and (5) the diffusing capacity calculated for each membrane. The data were examined at both absolute values and relative to each device's membrane surface area. In absolute terms, the HF 5000 performed better than the Univox in each category. However, when surface area was taken into account, the Univox was clearly more efficient with regard to oxygen transfer. We conclude from this evaluation that the Univox does not offer a satisfactory oxygen transfer 'buffer' for larger, more metabolically active patients (297 ml/min for the Univox and 447 ml/min for the HF 5000). The trade-offs that were made between design and performance features, with the Univox, were unacceptable.

A comparison of two oxygen transfer strategies: Bentley Univox and the Bard HF 5000

Fried

Bell-Thomson

1992

Oxygen transfer performance of a new Sarns membrane oxygenator

Fried

Bell-Thomson

1992

Oxygen transfer performance of the SMO 2, a new hollow-fibre membrane oxygenator from Sarns/3M, was evaluated. The maximum oxygen transfer of the SMO 2 (504 ml 0 2/min) was 57% higher than that for the SMO. This was true even though the membrane surface area increased by only 11% (1.8 m 2 to 2.0 m 2). The average gas phase-arterial oxygen gradient and the average shunt fraction was decreased by 35% and 30% respectively. The diffusing capacity of the SMO 2 was increased by 74% over the SMO. The oxygen transfer performance compared favourably, not only to the SMO, but to five other previously evaluated membrane oxygenators. It performed better in each category regardless of whether the result was expressed in absolute terms or relative to membrane surface area.

A comparison of gaseous emboli release in five membrane oxygenators

Beckley

Shinko

Sites³

1997

The purpose of this study was to compare the air handling capability of five currently used membrane oxygenators: the Avecor Affinity, the Bentley SpiralGold, the Medtronic Maxima Plus, the Sarns Turbo and the Sorin Monolyth M. A circuit was constructed to include a hardshell venous reservoir and roller pump. Pressure monitoring sites and ultrasonic microbubble detection probes were located proximal and distal to the oxygenator. An air injection/infusion site was provided proximal to the roller pump inlet. Each circuit was primed with fresh anticoagulated bovine blood, adjusted to a haematocrit of 25% and maintained at 38 +/- 1 degree C. Three different bolus amounts of air (10, 20 and 40 cm3) were injected at three blood flow rates (3, 4.5 and 6 l/min). A 1-min infusion of air delivered at 1 ml/s was also administered at three blood flow rates (3, 4.5 and 6 l/min). The hardshell reservoir was also completely emptied at each flow rate to simulate a massive air infusion. At any given blood flow, outlet microbubble counts were usually higher with greater bolus amounts of air. When indexed to the inlet bubble counts, the following average percent microbubbles were released from the outlet: Turbo 25%, Affinity 7%, Monolyth 5%, Maxima 3% and SpiralGold 1%. With a constant air infusion of 1 ml/s, greater outlet microbubble counts were associated with higher blood flow rates. Again, when indexed to the inlet bubble counts, the following average percent microbubbles were released from the outlet: Turbo 44%, Affinity 25%, Maxima 19%, Monolyth 16% and SpiralGold 0%. All oxygenators deprimed when the hardshell reservoir was emptied and all shed microbubbles into the outlet blood except the SpiralGold. The results of this study indicate that air handling is not a simple function of blood flow pattern (i.e. top to bottom versus bottom to top), but also includes dynamics associated with oxygenator design, fibre arrangement and flow resistance.