Characterization of the Ejector Pump Performance for the Assisted Bidirectional Glenn Procedure

Dongjie Jia,Mahdi Esmaily

doi:10.3390/fluids7010031

Abstract

This study introduces an algebraic model informed by computational fluid dynamics (CFD) simulations to investigate the performance of the assisted bidirectional Glenn (ABG) operation on a broad range of conditions. The performance of this operation, as measured by the superior vena cava (SVC) pressure, depends on the nozzle area in its ejector pump and the patient’s pulmonary vascular resistance (PVR). Using the developed algebraic model to explore this two-dimensional parameter space shows that the ejector pump can create a pressure difference between the pulmonary artery and the SVC as high as 5 mmHg. The lowest SVC pressure is produced at a nozzle area that decreases linearly with the PVR such that, at PVR =4.2 (Wood units-m2), there is no added benefit in utilizing the ejector pump effect (optimal nozzle area is zero, corresponding to the bidirectional Glenn circulation). At PVR =2 (Wood units-m2), the SVC pressure can be lowered to less than 4 mmHg by using an optimal nozzle area of ≈2.5 mm2. Regardless of the PVR, adding a 2 mm2 nozzle to the baseline bidirectional Glenn boosts the oxygen saturation and delivery by at least 15%. The SVC pressure for that 2 mm2 nozzle remains below 14 mmHg for all PVRs less than 7 Wood units-m2. The mechanical efficiency of the optimal designs consistently remains below 30%, indicating the potential for improvement in the future. A good agreement is observed between the algebraic model and high-fidelity CFD simulations.

Highlights

Infants born with a single ventricle undergo three stages of palliation to survive, starting with the first stage performed within a few days after birth
We developed a multi-fidelity approach that utilizes the computational fluid dynamics (CFD) simulations to tune an algebraic model, which in turn is used to predict the performance of the assisted bidirectional Glenn (ABG) circulation over a wide range of nozzle areas, Anozzle, and pulmonary vascular resistance (PVR)
pulmonary arteries (PA) pressure, PPA, which are the same parameters used to calculate the constants in the algebraic model

Summary

Introduction

Infants born with a single ventricle undergo three stages of palliation to survive, starting with the first stage performed within a few days after birth. This procedure establishes a systemic-to-pulmonary shunt, such as the modified Blalock–Taussig shunt (mBTS) [1,2], to create a parallel circulation between the systemic and pulmonary beds. The third stage operation, the Fontan procedure, further connects the inferior vena cava to the pulmonary arteries, after which the pulmonary and systemic circulations are placed in series [5,6]. The long-term mortality rate among single-ventricle patients remains high, owing to single ventricle failure, SVC syndrome, underdeveloped or unevenly developed pulmonary arteries, and other complications resulting from the first and second stage operations [7,8]

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Discussion

Conclusion