Multi-objective CFD optimization of an intermediate diffuser stage for PediaFlow pediatric ventricular assist device

TL;DR

This study uses multi-objective CFD optimization to improve the design of a pediatric ventricular assist device, balancing pressure recovery and hemolysis, resulting in a more efficient and biocompatible pump.

Contribution

It introduces an automated CFD-driven shape optimization method for a pediatric VAD diffuser, achieving a Pareto front of optimal designs with reduced hemolysis and improved efficiency.

Findings

Fewer blades (2-3) outperform more blades in both pressure recovery and hemolysis.

Optimized two-blade diffuser operates at lower RPM, increasing efficiency and reducing hemolysis.

Critical design dependencies include blade length and wrap angle affecting performance and hemocompatibility.

Abstract

Background: Computational fluid dynamics (CFD) has become an essential design tool for ventricular assist devices (VADs), where the goal of maximizing performance often conflicts with biocompatibility. This tradeoff becomes even more pronounced in pediatric applications due to the stringent size constraints imposed by the smaller patient population. This study presents an automated CFD-driven shape optimization of a new intermediate diffuser stage for the PediaFlow pediatric VAD, positioned immediately downstream of the impeller to improve pressure recovery. Methods: We adopted a multi-objective optimization approach to maximize pressure recovery while minimizing hemolysis. The proposed diffuser stage was isolated from the rest of the flow domain, enabling efficient evaluation of over 450 design variants using Sobol sequence, which yielded a Pareto front of non-dominated solutions. The selected best candidate was further refined using local T-search algorithm. We then incorporated the optimized front diffuser into the full pump for CFD verification and in vitro validation. Results: We identified critical dependencies where longer blades increased pressure recovery but also hemolysis, while the wrap angle showed a strong parabolic relationship with pressure recovery but a monotonic relationship with hemolysis. Counterintuitively, configurations with fewer blades (2-3) consistently outperformed those with more blades (4-5) in both metrics. The optimized two-blade design enabled operation at lower pump speeds (14,000 vs 16,000 RPM), improving hydraulic efficiency from 26.3% to 32.5% and reducing hemolysis by 31%. Conclusion: This approach demonstrates that multi-objective CFD optimization can systematically explore complex design spaces while balancing competing priorities of performance and hemocompatibility for pediatric VADs.