Differences Between Blood and a Newtonian Fluid on the Performance of a Hydrodynamic Bearing for Rotary Blood Pumps

Amaral, Felipe; Egger, Christina; Steinseifer, Ulrich; Schmitz‐Rode, Thomas

doi:10.1111/aor.12166

Cited by 8 publications

(8 citation statements)

References 17 publications

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“…Amaral et al. showed that the apparent viscosity in rotary blood pump gaps was lower than expected and assumes local changes in blood cell concentration to be the reason . To include cell exclusion effects is beyond the scope of this article, but this should be considered in future studies.…”

Section: Discussionmentioning

confidence: 98%

Multivariate Assessment of the Effect of Pump Design and Pump Gap Design Parameters on Blood Trauma

Graefe¹,

Henseler²,

Steinseifer³

2015

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Pump gaps are the most critical regions in a rotary blood pump when it comes to blood trauma in the form of hemolysis, protein destruction, and platelet activation. This study investigated six pump design parameters affecting the flow in a radial pump gap. A multivariate approach was employed to determine individual and quantitative parameter effects on blood trauma as well as parameter interactions. To consider the effect of shear stress and blood cell residence time, a validated numerical Lagrangian particle tracking approach was used. Based on the results, small-diameter pumps can be as blood compatible, if not more blood compatible, as large-diameter pumps as long as identical circumferential velocities and clearance gaps are maintained. Furthermore, the results indicate that an eccentric rotor position in the casing is not harmful and that a pressure difference generating washout flow and thereby reducing the cell residence time is of significant importance.

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Section: Discussionmentioning

confidence: 98%

Multivariate Assessment of the Effect of Pump Design and Pump Gap Design Parameters on Blood Trauma

Graefe¹,

Henseler²,

Steinseifer³

2015

Artificial Organs

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“…8, it was considered that the change of the gap flow did not affect plasma skimming in the SGB because there was no difference between mean HCT at the pressure head of 116 mm Hg and mean HCT at the pressure head of 140 mm Hg. Therefore, it is considered that this result indicated that the test rig of the SGB without the pump flow (21,22) will also be useful to evaluate plasma skimming in the SGB in the future. From the result of the present study, it is confirmed that plasma skimming occurred on the ridge region in the SGB of the blood pump.…”

Section: Discussionmentioning

confidence: 98%

“…Therefore, a partial cell exclusion of erythrocyte was considered, because the erythrocyte count decreased on the ridge region in the SGB with the narrow bearing gap. Amaral et al (22) also reported that the hydrodynamic force decreased when the bearing gap was narrow. In previous studies (21,22), it is reasonable to consider that the reduction of the hydrodynamic force in the SGB occurred due to the viscosity reduction, that is the decrease of hematocrit.…”

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confidence: 95%

“…Amaral et al (22) also reported that the hydrodynamic force decreased when the bearing gap was narrow. In previous studies (21,22), it is reasonable to consider that the reduction of the hydrodynamic force in the SGB occurred due to the viscosity reduction, that is the decrease of hematocrit. Therefore, these might be the first reports that plasma skimming occurs in the SGB.…”

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confidence: 95%

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Plasma Skimming in a Spiral Groove Bearing of a Centrifugal Blood Pump

et al. 2016

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Plasma skimming is a phenomenon in which discharge hematocrit is lower than feed hematocrit in microvessels. Plasma skimming has been investigated at a bearing gap in a spiral groove bearing (SGB), as this has the potential to prevent hemolysis in the SGB of a blood pump. However, it is not clear whether plasma skimming occurs in a blood pump with the SGB, because the hematocrit has not been obtained. The purpose of this study is to verify plasma skimming in an SGB of a centrifugal blood pump by developing a hematocrit measurement method in an SGB. Erythrocyte observation using a high-speed microscope and a bearing gap measurement using a laser confocal displacement meter was performed five times. In these tests, bovine blood as a working fluid was diluted with autologous plasma to adjust the hematocrit to 1.0%. A resistor was adjusted to achieve a pressure head of 100 mm Hg and a flow rate of 5.0 L/min at a rotational speed of 2800 rpm. Hematocrit on the ridge region in the SGB was measured using an image analysis based on motion image of erythrocytes, mean corpuscular volume, the measured bearing gap, and a cross-sectional area of erythrocyte. Mean hematocrit on the ridge region in the SGB was linearly reduced from 0.97 to 0.07% with the decreasing mean bearing gap from 38 to 21 μm when the rotational speed was changed from 2250 to 3000 rpm. A maximum plasma skimming efficiency of 93% was obtained with a gap of 21 μm. In conclusion, we succeeded in measuring the hematocrit on the ridge region in the SGB of the blood pump. Hematocrit decreased on the ridge region in the SGB and plasma skimming occurred with a bearing gap of less than 30 μm in the hydrodynamically levitated centrifugal blood pump.

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“…Amaral et al investigated suspension forces, flows and bearing torques of blood, and a Newtonian water glycerin mixture in a spiral groove hydrodynamic bearing. They found differences which can be explained by a lower apparent viscosity due to inhomogeneity of blood cell concentration .…”

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A Simple Method for the Investigation of Cell Separation Effects of Blood With Physiological Hematocrit Values

et al. 2014

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Even though the separation of blood into erythrocyte-rich and erythrocyte-poor areas is well known in physiological setups such as small vessels, it has recently come into focus in small gaps in cardiovascular applications. Studies show that separation effects occur, for example, in gaps in hydrodynamic bearings, where they can have a positive effect on hemolysis. Separation effects depend on the hematocrit value, but due to visualization issues, studies in small gaps used very low hematocrit values. In this study, a test setup and an evaluation method for the investigation of separation effects of blood with hematocrit values of 30, 45, and 60% were developed. The erythrocyte distribution was evaluated by means of gray scale value distribution. This principle is based on the fact that an erythrocyte-rich region is more opaque than an erythrocyte-poor region. The experimental setup is designed in a way that no further processes (e.g., fluorescence labeling) need to be carried out which might change the properties of the membrane of the erythrocytes, and therefore their flow properties. Additionally, the method is executable with basic laboratory equipment, which makes it applicable for many laboratories. To validate the feasibility of the method, the influence of the diameter and the flow rate on the migration of erythrocytes were studied in micro channels for three different physiological hematocrit values. Even though no individual cells were traced, plasma layer and areas of high erythrocyte concentration could be identified. Dependencies of the erythrocyte distribution on flow rate and channel diameter were validated. The influence of the hematocrit value was demonstrated as well and showed the hematocrit value to be a crucial factor when investigating cell separation. The experimental results were consistent with findings in the literature. As the developed method is suitable for physiological hematocrit values and easy to handle, it provides an optimal basis for cell separation studies in gap models with whole blood, for example, hydrodynamic bearings, where it can be used to optimize these devices.

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Differences Between Blood and a Newtonian Fluid on the Performance of a Hydrodynamic Bearing for Rotary Blood Pumps

Cited by 8 publications

References 17 publications

Multivariate Assessment of the Effect of Pump Design and Pump Gap Design Parameters on Blood Trauma

Multivariate Assessment of the Effect of Pump Design and Pump Gap Design Parameters on Blood Trauma

Plasma Skimming in a Spiral Groove Bearing of a Centrifugal Blood Pump

A Simple Method for the Investigation of Cell Separation Effects of Blood With Physiological Hematocrit Values

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