Comparison of hollow-fiber membrane oxygenators with different perfusion modes during normothermic and hypothermic CPB in a simulated neonatal model

Purpose: The objectives of this investigation were (1) to compare two hollow-fiber membrane oxygenators (Capiox Baby RX versus Lilliput 1-D901) in terms of pressure drops and surplus hemodynamic energy (SHE) during normothermic and hypothermic cardiopulmonary bypass (CPB) in a simulated neonatal model; and (2) to evaluate pulsatile and non-pulsatile perfusion modes for each oxygenator in terms of SHE levels. Methods: In a simulated patient, CPB was initiated at a constant pump flow rate of 500 ml./min. The circuit was primed with fresh bovine blood. After 5 min of normothermic CPB, the pseudo-patient was cooled down to 25 degrees C for 10 min followed by 30 min of hypothermic CPB. The pseudo-patient then underwent 10 min of rewarming and 5 min of normothermic CPB. At each experimental site (pre- and post-oxygenator and pre-aortic cannula), SHE was calculated using the following formula (SHE (ergs/ cm(3)) = 1332 [((integral fpdt)/(integral fdt)) - mean arterial pressure]) (f = pump flow and p = pressure). A linear mixed-effects model that accounts for the correlation among repeated measurements was fit to the data to assess differences in SHE between oxygenators, pumps, and sites. Tukey's multiple comparison procedure was used to adjust p-values for post-hoc pairwise comparisons. Results: The pressure drops in the Capiox group compared to the Lilliput group were significantly lower during hypothermic non-pulsatile (21.3 +/- 0.5 versus 50.7 +/- 0.9 mmHg, p < 0.001) and pulsatile (22 +/- 0.0 versus 53.3 +/- 0.5 mmHg, p < 0.001) perfusion, respectively. Surplus hemodynamic energy levels were significantly higher in the pulsatile group compared to the non-pulsatile group, with Capiox (1655 +/- 92 versus 10 008 +/- 1370 ergs/cm(3), p < 0.001) or Lilliput (1506 +/- 112 versus 7531 +/- 483 ergs/cm(3), p < 0.001) oxygenators. During normothermic CPB, both oxygenators had patterns similar to those observed under hypothermic conditions. Conclusions: The Capiox oxygenator had a significantly lower pressure drop in both pulsatile and non-pulsatile perfusion modes. For each oxygenator, the SHE levels were significantly higher in the pulsatile mode.