BackgroundExtracorporeal carbon dioxide removal (ECCO2R) uses an extracorporeal circuit to directly remove carbon dioxide from the blood either in lieu of mechanical ventilation or in combination with it. While the potential benefits of the technology are leading to increasing use, there are very real risks associated with it. Several studies demonstrated major bleeding and clotting complications, often associated with hemolysis and poorer outcomes in patients receiving ECCO2R. A better understanding of the risks originating specifically from the rotary blood pump component of the circuit is urgently needed.MethodsHigh-resolution computational fluid dynamics was used to calculate the hemodynamics and hemocompatibility of three current rotary blood pumps for various pump flow rates.ResultsThe hydraulic efficiency dramatically decreases to 5–10% if operating at blood flow rates below 1 L/min, the pump internal flow recirculation rate increases 6–12-fold in these flow ranges, and adverse effects are increased due to multiple exposures to high shear stress. The deleterious consequences include a steep increase in hemolysis and destruction of platelets.ConclusionsThe role of blood pumps in contributing to adverse effects at the lower blood flow rates used during ECCO2R is shown here to be significant. Current rotary blood pumps should be used with caution if operated at blood flow rates below 2 L/min, because of significant and high recirculation, shear stress, and hemolysis. There is a clear and urgent need to design dedicated blood pumps which are optimized for blood flow rates in the range of 0.5–1.5 L/min.

The artificial placenta as a fascinating treatment alternative for neonatal lung failure has been the subject of clinical research for over 50 years. Pumpless systems have been in use since 1986. However, inappropriate dimensioning of commercially available oxygenators has wasted some of the theoretical advantages of this concept. Disproportional shunt fractions can cause congestive heart failure. Blood priming of large oxygenators and circuits dilutes fetal hemoglobin (as the superior oxygen carrier), is potentially infectious, and causes inflammatory reactions. Flow demands of large extracorporeal circuits require cannula sizes that are not appropriate for use in preterm infants. NeonatOx, a tailored low-volume oxygenator for this purpose, has proven the feasibility of this principle before. We now report the advances in biological performance of a refined version of this specialized oxygenator.

Only a very small portion of end-stage organ failures can be treated by transplantation because of the shortage of donor organs. Although artificial long-term organ support such as ventricular assist devices provide therapeutic options serving as a bridge-to-transplantation or destination therapy for endstage heart failure, suitable long-term artificial lung systems are still at an early stage of development. Although a shortterm use of an extracorporeal lung support is feasible today, the currently available technical solutions do not permit the long-term use of lung replacement systems in terms of an implantable artificial lung. This is currently limited by a variety of factors: biocompatibility problems lead to clot formation within the system, especially in areas with unphysiological flow conditions. In addition, proteins, cells, and fibrin are deposited on the membranes, decreasing gas exchange performance and thus, limiting long-term use. Coordinated basic and translational scientific research to solve these problems is therefore necessary to enable the long-term use and implantation of an artificial lung. Strategies for improving the biocompatibility of foreign surfaces, for new anticoagulation regimes, for optimization of gas and blood flow, and for miniaturization of these systems must be found. These strategies must be validated by in vitro and in vivo tests, which remain to be developed. In addition, the influence of long-term support on the pathophysiology must be considered. These challenges require well-connected interdisciplinary teams from the natural and material sciences, engineering, and medicine, which take the necessary steps toward the development of an artificial implantable lung. ASAIO Journal XXX; XX:00-00.

Computational fluid dynamics (CFD) is used to simulate blood flow inside the fiber bundles of oxygenators. The results are interpreted in terms of flow distribution, e.g., stagnation and shunt areas. However, experimental measurements that provide such information on the local flow between the fibers are missing. A transparent model of an oxygenator was built to perform particle image velocimetry (PIV), to perform the experimental validation. The similitude theory was used to adjust the size of the PIV model to the minimal resolution of the PIV system used (scale factor 3.3). A standard flow of 80 mL/min was simulated with CFD for the real oxygenator and the equivalent flow of 711 mL/min, according to the similitude theory, was investigated with PIV. CFD predicts the global size of stagnation and shunt areas well, but underestimates the streamline length and changes in velocities due to the meandering flow around the real fibers in the PIV model. Symmetrical CFD simulation cannot consider asymmetries in the flow, due to manufacturing-related asymmetries in the fiber bundle. PIV could be useful for validation of CFD simulations; measurement quality however must be improved for a quantitative validation of CFD results and the investigation of flow effects such as tortuosity and anisotropic flow behavior.