Antithrombogenic Properties of a Monopivot Magnetic Suspension Centrifugal Pump for Circulatory Assist

Numerical simulation of the leakage flow of the hydrodynamically levitated centrifugal blood pump for extracorporeal mechanical circulatory support systems

Extracorporeal centrifugal pumps are widely used in various forms of mechanical circulatory support, including extracorporeal membrane oxygenation and ventricular assist device. A durable centrifugal pump was developed by implementing a new hydrodynamic bearing design that prevents the impeller from touching to the casing wall and provides sufficient washout through the pump to prevent thrombus formation in the pump. The hydrodynamic bearings of the pump are composed of dual annular paths located on both sides of the impeller. Computational fluid dynamics analyses were performed on the flow field inside the pump to estimate the leakage flow through the gap and its impact on the pump efficiency and biocompatibility. The calculations were performed for motor speeds from 3000 to 5000 rpm and flow rates from 1.0 to 9.0 L/min. The leakage flow increased linearly with increasing pressure head of the pump, and the total leakage flow ranged from 2.0 to 27.3% of the total flow. The average wall shear stresses in the casing bottom ranged from 10.6 to 40.9 Pa. The leakage flow of the centrifugal pump with the hydrodynamically levitated impeller had a measurable impact on hydraulic energy losses while enhancing the washout flow to achieve good anti-thrombogenicity.

Impact of volute design features on hemodynamic performance and hemocompatibility of centrifugal blood pumps used in ECMO

BACKGROUND

The centrifugal blood pump volute has a significant impact on its hemodynamic performance hemocompatibility. Previous studies about the effect of volute design features on the performance of blood pumps are relatively few.

METHODS

In the present study, the computational fluid dynamics (CFD) method was utilized to evaluate the impact of volute design factors, including spiral start position, volute tongue radius, inlet height, size, shape and diffuser pipe angle on the hemolysis index and thrombogenic potential of the centrifugal blood pump.

RESULTS

Correlation analysis shows that flow losses affect the hemocompatibility of the blood pump by influencing shear stress and residence time. The closer the spiral start position of the volute, the better the hydraulic performance and hemocompatibility of the blood pump. Too large or too small volute inlet heights can worsen hydraulic performance and hemolysis, and higher volute inlet height can increase the thrombogenic potential. Small volute sizes exacerbate hemolysis and large volute sizes increase the thrombogenic risk, but volute size does not affect hydraulic performance. When the diffuser pipe is tangent to the base circle of the volute, the best hydraulic performance and hemolysis performance of the blood pump is achieved, but the thrombogenic potential is increased. The trapezoid volute has poor hydraulic performance and hemocompatibility. The round volute has the best hydraulic and hemolysis performance, but the thrombogenic potential is higher than that of the rectangle volute.

CONCLUSION

This study found that the hemolysis index shows a significant correlation with spiral start position, volute size, and diffuser pipe angle. Thrombogenic potential exhibits a good correlation with all the studied volute design features. The flow losses affect the hemocompatibility of the blood pump by influencing shear stress and residence time. The finding of this study can be used to guide the optimization of blood pump for improving the hemodynamic performance and hemocompatibility.

Cell adhesion on phase-separated surface of block copolymer composed of poly(2-methacryloyloxyethyl phosphorylcholine) and poly(dimethylsiloxane)

We investigated the morphological effect of phase-separated block copolymer surfaces composed of poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) (PMPC) and poly(dimethylsiloxane) (PDMS) on protein adsorption and cell adhesion behavior. We observed three different types of phase-separated surface morphologies by TEM and AFM. The elemental composition of phosphorus on the surface increases with the PMPC composition. Furthermore, the polymer surface formed by a block copolymer-containing a higher MPC unit composition shows a slightly lower static water contact angle. This result indicates that the elemental surface ratio of the surface depends on the MPC composition in the block copolymer. Protein adsorption tests revealed that only hydrophobic PDMS domains showed selective protein adsorption. Cell adhesion tests revealed that the number of adhered cells increased with increasing hydrophobic PDMS domain size of block copolymers in serum-containing media. In contrast, no cells adhered onto block copolymer surfaces in serum-free media, whereas a large amount of adhered cells were observed on the hydrophobic PDMS surface. This result indicates that segregated hydrophobic domains on a biocompatible PMPC surface strongly affect serum protein adsorption, thereby promoting considerable cell adhesion, although the surface is hydrophilic. Thus, both the composition of MPC units and the segregated hydrophobic surface morphology are important considerations in biomaterial surface design.