title: Flow characteristics of the Hemopump: an experimental in vitro study.
abstract: BACKGROUND
  The Hemopump (DLP/Medtronic) has been in clinical use for about 7 years. There is still no adequate way of determining actual output from the three available pump systems in the clinical situation. If the pump is completely stopped during weaning from the device, there is a possibility of back-leakage through the pump, endangering the patient from regurgitation into the left ventricle. It can also make it more difficult to judge the recovery of heart function because of a volume load of the left ventricle. The aim of this study was to evaluate in a standardized, experimental in vitro model the output from three different-sized Hemopump catheters at various pressure levels and to quantify the back-flow through the pumps.
  
  
  METHODS
  The Hemopump models were tested in an in vitro study regarding total outflow at various speeds at three pressure levels. The back-flow through the pumps was also measured with the pumps at a complete stop.
  
  
  RESULTS
  The outflow from the Hemopumps ranged from 0.4 to 4.5 L/min, depending on which pump and speed were used. Variations in total output, depending on speed and various pressure settings, could be up to 0.4 L/min. Back-flow through the pump into the left ventricle may be as great as 1.6 L/min.
  
  
  CONCLUSIONS
  The flow outputs from the different Hemopump models were reproducible over time and were closely related to the resistance of the model. The Hemopump, if not running, can induce substantial regurgitation through the pump into the left ventricle.
authors.affiliation: Department of Cardiothoracic Anesthesiology, Linköping Heart Center, University of Linköping, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Wulff
authors.forename: U
authors.initials: U
authors.lastname: Lönn
authors.forename: K Y
authors.initials: KY
authors.lastname: Keck
authors.forename: B
authors.initials: B
authors.lastname: Wranne
authors.forename: P
authors.initials: P
authors.lastname: Ask
authors.forename: B
authors.initials: B
authors.lastname: Peterzén
authors.forename: H
authors.initials: H
authors.lastname: Casimir-Ahn
mesh_terms: D001783:Blood Flow Velocity; D004867:Equipment Design; D006353:Heart-Assist Devices; D006439:Hemodynamics; D006801:Humans; D008955:Models, Cardiovascular