PULM3: Gas Transfer Efficiency And Hemocompatibility Assessment In Microfluidic Blood Oxygenators

Background: Microfluidic lung support technology is a promising alternative to standard ECMO due to geometry-driven enhancements of gas transfer efficiencies and physiologically-inspired designs that improve hemocompatibility. We report a microfluidic oxygenator prototype device, BLOx2-R1, that achieves high gas transfer at 100 mL/min blood flow per layer. This flow rate per layer is ten times higher than the largest capacity reported by other microfluidic oxygenators, and four times higher than devices previously reported by our group. Clinical translation of this microfluidic oxygenation technology requires high capacity in terms of blood flow rate per layer, in order to achieve practical scaling of the device. Methods: The device was designed to maintain control over shear stress, and performance modeled via computational dynamic simulations. Fabrication utilized high precision-machined metal master molds, silicone microreplication of vascular and oxygen layers, and an intervening gas permeable membrane. Oxygen transfer was evaluated at 100% oxygen concentration and blood flow rates of 0 – 150 mL/min, while monitoring oxygen partial pressures in the blood. In a 6 hour hemocompatibility test evaluating pressure drop, platelet count, and plasma-free hemoglobin, the device was assessed at 100 mL/min flow rate with heparinized swine donor blood (target ACT 180 – 220 seconds.) Results and Conclusion: BLOx2-R1 devices reached 4 volume percent oxygen transfer at 100 – 150 mL/min blood flow rates depending on oxygen back pressure (0 – 400 mmHg), translating to increasing the blood oxygen level from venous conditions to 95% oxygen saturation. In 6 hour studies, the device remained patent and blood pressure remained steady near 112 mmHg across the duration of the study. This blood pressure drop is an order of magnitude lower per unit blood flow rate than our earlier designs. This data shows that our microfluidic technology has the potential to benefit extracorporeal lung support technologies for acute lung injury. Sponsor Acknowledgement Statement: This work was supported by the U.S Army Medical Research and Development Command through the Congressional Directed medical Research Program, termed BLOx, under the award number W81XWH-19-1-0518. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the Department of the Army. Figure 1. The BLOx2-R1 design (left) supported efficient oxygen transfer up to 150 ml/min flow rates as a function of back pressure (right).