title: A two-stage rotary blood pump design with potentially lower blood trauma: a computational study.
abstract: OBJECTIVE
  In current rotary blood pumps, complications related to blood trauma due to shear stresses are still frequently observed clinically. Reducing the rotor tip speed might decrease blood trauma. Therefore, the aim of this project was to design a two-stage rotary blood pump leading to lower shear stresses.
  
  
  METHODS
  Using the principles of centrifugal pumps, two diagonal rotor stages were designed with an outer diameter of 22 mm. The first stage begins with a flow straightener and terminates with a diffusor, while a volute casing behind the second stage is utilized to guide fluid to the outlet. Both stages are combined into one rotating part which is pivoted by cup-socket ruby bearings. Details of the flow field were analyzed employing computational fluid dynamics (CFD). A functional model of the pump was fabricated and the pressure-flow dependency was experimentally assessed.
  
  
  RESULTS
  Measured pressure-flow performance of the developed pump indicated its ability to generate adequate pressure heads and flows with characteristic curves similar to centrifugal pumps. According to the CFD results, a pressure of 70 mmHg was produced at a flow rate of 5 L/min and a rotational speed of 3200 rpm. Circumferential velocities could be reduced to 3.7 m/s as compared to 6.2 m/s in a clinically used axial rotary blood pump. Flow fields were smooth with well-distributed pressure fields and comparatively few recirculation or vortices. Substantially smaller volumes were exposed to high shear stresses &gt;150 Pa.
  
  
  CONCLUSIONS
  Hence, blood trauma might be reduced with this design. Based on these encouraging results, future in vitro investigations to investigate actual blood damage are intended.
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Bente
authors.initials: B
authors.lastname: Thamsen
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Mevert
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Lommel
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Philip
authors.initials: P
authors.lastname: Preikschat
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Gaebler
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Deutsches Herzzentrum Berlin, Berlin - Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Krabatsch
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kertzscher
authors.affiliation: Department of Cardiothoracic and Vascular Surgery, Deutsches Herzzentrum Berlin, Berlin - Germany.
authors.forename: Ewald
authors.initials: E
authors.lastname: Hennig
authors.affiliation: Biofluid Mechanics Laboratory, Charité Universitätsmedizin Berlin, Berlin - Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Affeld
mesh_terms: D004867:Equipment Design; D004912:Erythrocytes; D006353:Heart-Assist Devices; D006461:Hemolysis / Q000502:physiology*; D006801:Humans; D057446:Hydrodynamics; D013314:Stress, Mechanical