Pediatric Circulatory Support

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The PediaFlow consortium is developing a mixed-flow turbodynamic (continuous flow) ventricular assist device utilizing a magnetically levitated impeller capable of producing 0.3-1.5 liters per minute (LPM) of blood flow for supporting infants and small children weighing 3-15 kg up to 6 months with minimal anticoagulation requirement and optimal biocompatibility. Over 20 design variations were initially considered, with three pump topologies selected for further design refinement and evaluation. The three designs, two centrifugal and one mixed-flow pumps, were judged based on a multi-component objective function which factored several criteria including anatomic fit, estimated biocompatibility, heat generation and transfer, magnetically levitated suspension robustness, and manufacturability. This evaluation led to selection of the mixed-flow configuration. The design was improved using computational fluid dynamics to minimize flow-induced blood damage via modification of the geometry of the predicted blood flow path. The housing was modified to improve surgical fixation. A transparent replica of the blood flow path was built to perform validation of the computer predictions by flow visualization analyses. Other ongoing efforts are focused on controller development, materials selection, biocompatible coating application, nanotechnology based infection control, cannula design, and overall assessment of hemodynamic performance and cellular biocompatibility. Fabrication and assembly of initial components (Figures 1, 2) produced a finalized first generation pump design (PediaFlow¿ GEN1) that is 51 mm in length and 28 mm in diameter with 5 mm diameter inlet and outlet conduits. The mass is approximately 100 grams. At a nominal flow rate of 0.5 LPM, generating 110 mm Hg pressure rise, and 8,000 RPM rotor speed, the shaft power is approximately 0.9 Watts leading to an overall efficiency estimate of 11%.