title: The role of venous valves in pressure shielding.
abstract: BACKGROUND
  It is widely accepted that venous valves play an important role in reducing the pressure applied to the veins under dynamic load conditions, such as the act of standing up. This understanding is, however, qualitative and not quantitative. The purpose of this paper is to quantify the pressure shielding effect and its variation with a number of system parameters.
  
  
  METHODS
  A one-dimensional mathematical model of a collapsible tube, with the facility to introduce valves at any position, was used. The model has been exercised to compute transient pressure and flow distributions along the vein under the action of an imposed gravity field (standing up).
  
  
  RESULTS
  A quantitative evaluation of the effect of a valve, or valves, on the shielding of the vein from peak transient pressure effects was undertaken. The model used reported that a valve decreased the dynamic pressures applied to a vein when gravity is applied by a considerable amount.
  
  
  CONCLUSIONS
  The model has the potential to increase understanding of dynamic physical effects in venous physiology, and ultimately might be used as part of an interventional planning tool.
authors.affiliation: Academic Unit of Medical Physics, School of Medicine and Biomedical Sciences, The University of Sheffield, Sheffield, UK. c.zervides@hotmail.co.uk
authors.forename: Constantinos
authors.initials: C
authors.lastname: Zervides
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Narracott
authors.forename: Patricia V
authors.initials: PV
authors.lastname: Lawford
authors.forename: David R
authors.initials: DR
authors.lastname: Hose
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003198:Computer Simulation; D004548:Elasticity; D006112:Gravitation; D006801:Humans; D008955:Models, Cardiovascular; D033081:Shear Strength; D013314:Stress, Mechanical; D014680:Veins / Q000502:physiology*