Research of flow dynamics and occlusion condition in roller pump systems used for ventricular assist

Abstract

Roller pumps have been widely used in the ventricular assist field for many years, while the significant hemolysis caused by its mechanical stress is still a fundamental problem. Although the usual under‐occlusion setting was considered as an effective method to reduce the hemolysis rate, its nonocclusive condition of the whole process may cause serious backflow results, which exactly places many restrictions on this method. In this study, the simulation experiments based on computational fluid dynamics (CFD) is conducted, and the occlusion angle is proposed and used to explore a more reliable adjustment form of the occlusion condition. The parameterized geometry of a roller pump is established based on the occlusion angle and other parameters. In order to simulate the motion of the roller, the dynamic mesh mode is introduced to the CFD model, and the analytic formulations used to determine the boundary position are derived. In the whole operation process of the roller pump, four feature positions of the rollers were focused and extracted, and the flow characteristics and the shear stress distribution at these positions were demonstrated. It was found that the entry and exit of the rollers could cause clear shear stress peak, especially when one roller entered, the peak got extremely high. Furthermore, the roller pumps with different occlusion angles were compared, and the results showed that decreasing the occlusion angle could lead to a notable decrease in the amplitude and range of high shear stress and the hemolysis index with a small loss of the occlusion duration. It can be concluded that appropriately decreasing the occlusion angle may be an effective method to alleviate the hemolysis which should be given more attention.

Suppression of flow pulsations and energy consumption of a drug delivery roller pump based on a novel tube design

“…Similar trends were predicted elsewhere. [7][8][9][10] More specifically, the outlet flow rate starts being reduced from φ = 130°(Tube B) or 150°(Tube A and C) till φ = 50°(Tube A) or 70°(Tube B and C). Higher deceleration rates occur in the interval φ = 0°to φ = 50°for Tube A and B, and from φ = 30°to φ = 70°for Tube C. The higher flow rate reduction is attributed to the increase of the tube volume during the disengagement phase, so that eventually a smaller fluid mass is discharged at the pump outlet.…”

“…The issue of blood damage has been studied by several groups using computational fluid mechanics (CFD) and making the assumption that the flow is two dimensional. [7][8][9] The CFD treatment of the flow in a peristaltic pump needs a lot of computational resources in order to capture the details of the three dimensional (3D) flow field, and in particular, the region around the moving stenosis. Moreover, it has to be stressed that there is no CFD code nowadays that can solve the flow if the tube is deeply occluded due to singularities which appear when the computational cells touch each other at the occluded part of the tube.…”

A method of parameter estimation for cardiovascular hemodynamics based on deep learning and its application to personalize a reduced‐order model

“…Related models of hemodynamics have achieved great effects in a variety of applications, including cardiac output (CO) monitoring, 5,6 aneurysm diagnosis, 7 calculation of coronary fractional flow reserve (FFR), 8 and evaluation of artificial assistive devices. 9 It is believed that using these models can help improve the prediction of cardiovascular activities, and more importantly, it provides a convincing mechanism explanation for this prediction. 10 Especially, hemodynamic mathematical modeling usually contains three different scales, which have led to three typical models respectively, including 0-dimensional (0-D) model, 11 1-dimensional (1-D) model, 12 and 3-dimensional (3-D) model.…”

“…Among these models, cardiovascular hemodynamic modeling has become one of the most active areas, considering its close relationship with clinical routine monitoring. Related models of hemodynamics have achieved great effects in a variety of applications, including cardiac output (CO) monitoring, 5,6 aneurysm diagnosis, 7 calculation of coronary fractional flow reserve (FFR), 8 and evaluation of artificial assistive devices 9 . It is believed that using these models can help improve the prediction of cardiovascular activities, and more importantly, it provides a convincing mechanism explanation for this prediction 10 .…”

Roller pump reverse flow-directed dynamic occlusiveness: towards precision in perfusion

“…A significant variable, possibly impacting this phenomenon, is the degree of pump occlusion. Despite its known association with haemolysis, inadequate occlusion (both tight occlusive and non-occlusive settings) remains an unaddressed issue, with no international standards for adjusting occlusiveness [ 3 ]. The actual flow delivered by the master RP is a function of several aspects of CPB management, including device-related, disposable-related, patient-related, or procedure-related factors, such as pump model, tubing material (silicone or PVC) and diameter, temperature, blood viscosity, oxygenator model, design and pressure drop, the use of vacuum-assisted venous drainage and the choice between continuous or pulsatile flow.…”