title: Venous cannula performance assessment in a realistic caval tree model.
abstract: OBJECTIVE
  A new caval tree system was designed for realistic in vitro simulation. The objective of our study was to assess cannula performance for virtually wall-less versus standard percutaneous thin-walled venous cannulas in a setting of venous collapse in case of negative pressure.
  
  
  METHODS
  For a collapsible caval model, a very flexible plastic material was selected, and a model with nine afferent veins was designed according to the anatomy of the vena cava. A flow bench was built including a lower reservoir holding the caval tree, built by taking into account the main afferent vessels and their flow provided by a reservoir 6 cm above. A cannula was inserted in this caval tree and connected to a centrifugal pump that, in turn, was connected to a reservoir positioned 83 cm above the second lower reservoir (after-load = 60 mmHg). Using the same pre-load, the simulated venous drainage for cardiopulmonary bypass was realized using a 24 F wall-less cannula (Smartcanula) and 25 F percutaneous cannula (Biomedicus), and stepwise increased augmentation (1500 RPM, 2000 and 2500 RPM) of venous drainage.
  
  
  RESULTS
  For the thin wall and the wall-less cannulas, 36 pairs of flow and pressure measurements were realized for three different RPM values. The mean Q-values at 1500, 2000 and 2500 RPM were: 3.98 ± 0.01, 6.27 ± 0.02 and 9.81 ± 0.02 l/min for the wall-less cannula (P <0.0001), versus 2.74 ± 0.02, 3.06 ± 0.05, 6.78 ± 0.02 l/min for the thin-wall cannula (P <0.0001). The corresponding inlet pressure values were: -8.88 ± 0.01, -23.69 ± 0.81 and -70.22 ± 0.18 mmHg for the wall-less cannula (P <0.0001), versus -36.69 ± 1.88, -80.85 ± 1.71 and -101.83 ± 0.45 mmHg for the thin-wall cannula (P <0.0001). The thin-wall cannula showed mean Q-values 37% less and mean P values 26% more when compared with the wall-less cannula (P <0.0001).
  
  
  CONCLUSIONS
  Our in vitro water test was able to mimic a negative pressure situation, where the wall-less cannula design performs better compared with the traditional thin-wall cannula.
authors.affiliation: Cardiovascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland.
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.affiliation: Cardiovascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland saad.abdel-aayed@chuv.ch.
authors.forename: Saad
authors.initials: S
authors.lastname: Abdel-Sayed
authors.affiliation: Cardiovascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland.
authors.forename: Denis
authors.initials: D
authors.lastname: Berdajs
authors.affiliation: Cardiovascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland.
authors.forename: Enrico
authors.initials: E
authors.lastname: Ferrari
authors.affiliation: Cardiovascular Research, Department of Surgery and Anesthesiology, CHUV, Lausanne, Switzerland.
authors.forename: Ludwig K
authors.initials: LK
authors.lastname: von Segesser
mesh_terms: D001783:Blood Flow Velocity; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000295:instrumentation*; D002406:Catheterization, Peripheral / Q000009:adverse effects / Q000295:instrumentation*; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D008422:Materials Testing; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D012039:Regional Blood Flow; D062666:Vascular Access Devices; D014684:Venae Cavae / Q000033:anatomy & histology*; D014690:Venous Pressure
keywords: Atrial chatter; Cardiopulmonary bypass; Caval collapse; Venous cannula; Venous drainage