Show simple item record

dc.contributor.author
Boës, Stefan
dc.contributor.supervisor
Meboldt, Mirko
dc.contributor.supervisor
Kurtcuoglu, Vartan
dc.contributor.supervisor
Woodard, John Campbell
dc.date.accessioned
2019-01-07T10:52:40Z
dc.date.available
2019-01-07T09:39:27Z
dc.date.available
2019-01-07T10:52:40Z
dc.date.issued
2018
dc.identifier.uri
http://hdl.handle.net/20.500.11850/313914
dc.identifier.doi
10.3929/ethz-b-000313914
dc.description.abstract
Rotary blood pumps (RBPs) are implanted into patients with end-stage heart failure to support the left heart by pumping blood from the left ventricle to the aorta. Although the survival rate of patients supported with RBPs has increased substantially over the last decades, patients still suffer from a high incidence of adverse events such as infection, major bleeding or cerebral strokes. Many of these adverse events can be linked to the hemocompatibility of the RBP. And hemocompatibility, in turn, is closely related to the flow conditions in the RBP. The design of RBPs is based on the same principles as industrial turbomachinery. Whereas design rules and guidelines for turbomachinery design in industrial applications have been collected and refined over many decades, specific design knowledge for RBPs is rare and subjected to additional requirements different from industrial application. These requirements include the sufficient hemocompatibility of the pumps and the operation under dynamic conditions of the clinical application. Thus, this thesis aims to contribute to the design knowledge for RBPs in those two areas. The overall objective of this thesis is twofold: (I.) to model and compare the hydraulic behavior of RBPs under realistic pressure conditions of the cardiac cycle and (II.) to relate effects of typical RBP design parameters to indicators of hemocompatibility. In order to obtain repeatable and accurate in vitro experiments, a viscosity control was implemented into a mock circulation. The results of this thesis have implications for the design and testing of new RBPs, but also for the modeling and analysis procedures of existing RBPs. To investigate the hydraulic characteristics of implantable RBPs, an universal mathematical model of the static and dynamic hydraulic pump behavior was developed. This model was then used to systematically compare four current RBPs at clinically relevant, dynamic operating conditions. The model structure was based on principles of turbomachinery, including the low and backflow region, and it proved to be applicable to each of the investigated RBPs. The determined hydraulic behavior of the RBPs did not show any characteristic distinction between axial-flow and radial-flow pumps. For the simulated support conditions it was observed that the flow pulsatility varied greatly for the different RBPs and backflow occurred during partial support conditions for three out of the four RBPs. To investigate the influence of the design parameters of an RBP on hemocompatibility indicators, an RBP design was developed using industrial guidelines. Selected design parameters of this RBP design were varied systematically and the resulting effects on flow field and hydraulic performance were simulated using computational fluid dynamics. The flow fields were analyzed based on Eulerian and Lagrangian features, shear stress histograms and six indicators of hemocompatibility. Potentially damaging shear stress conditions were found for larger gap size and a higher number of blades. The extent of stagnation and recirculation zones was reduced with lower numbers of blades and a semi-open impeller, but it was increased with smaller clearance gaps. The Lagrangian hemolysis index showed a negative correlation with hydraulic efficiency and no correlation with the Eulerian threshold-based metric for hemolysis. In order to obtain repeatable and accurate in vitro experiments for the previously mentioned investigations, the control of the fluid viscosity was implemented in an existing mock circulation. This accounts for evaporation and temperature changes as well as for mimicking different viscosities of blood. The implemented viscosity control was then used for investigating an implantable RBP at different viscosities in the range of blood viscosities of patients with heart assist devices. For average support conditions, the influence on the measured head pressure was negligible, whereas the measured motor current deviated noticeably for higher speeds.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.title
Hydraulic Characteristics and Flow-field Related Hemocompatibility of Rotary Blood Pump Designs
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
ethz.size
159 p.
en_US
ethz.identifier.diss
25497
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02665 - Inst. f. Design, Mat. und Fabrikation::03943 - Meboldt, Mirko / Meboldt, Mirko
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02665 - Inst. f. Design, Mat. und Fabrikation::03943 - Meboldt, Mirko / Meboldt, Mirko
en_US
ethz.date.deposited
2019-01-07T09:39:35Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2019-01-07T10:52:51Z
ethz.rosetta.lastUpdated
2019-01-07T10:52:51Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.atitle=Hydraulic%20Characteristics%20and%20Flow-field%20Related%20Hemocompatibility%20of%20Rotary%20Blood%20Pump%20Designs&rft.date=2018&rft.au=Bo%C3%ABs,%20Stefan&rft.genre=unknown&rft.btitle=Hydraulic%20Characteristics%20and%20Flow-field%20Related%20Hemocompatibility%20of%20Rotary%20Blood%20Pump%20Designs
 Search via SFX

Files in this item

Thumbnail

Publication type

Show simple item record