title: Venous flow restriction: the role of vein wall motion in venous admixture.
abstract: OBJECTIVE
  There are wide differences in flow between vascular beds at rest, even more during stress. The hydrodynamic energy (Energy grade line or EGL) of venous outflows must also vary considerably between vascular beds. We explored the mechanism of venous admixture of differing energy flows using a mechanical model.
  
  
  METHODS
  The model simulated two venous flows coalescing at a venous junction and then flowing through collapsible venous pumps. Flow rates and pressures were monitored when the venous pumps were full (steady state) and when they were compressed and allowed to refill inducing wall motion (pump flow).
  
  
  RESULTS
  With increasing EGL differences between two coalescing venous flows, reduction or cessation (venous flow restriction) of the weaker flow occurred during steady state; higher base EGL of both flows ameliorated venous flow restriction and lower base EGL the opposite. Outflow obstruction favoured venous flow restriction. Pump action in the vicinity of the venous junction abolished venous flow restriction and maximized both venous flows.
  
  
  CONCLUSIONS
  The model suggests a pivotal role for vein wall motion in venous admixture and regional perfusion. Observations in the model are explained on the basis of network flow principles and collapsible tube mechanics.
authors.affiliation: River Oaks Hospital and University of Mississippi Medical Center, Jackson, MS 39232, USA.
authors.forename: S
authors.initials: S
authors.lastname: Raju
authors.forename: G
authors.initials: G
authors.lastname: Cruse
authors.forename: M
authors.initials: M
authors.lastname: Berry
authors.forename: S
authors.initials: S
authors.lastname: Owen
authors.forename: E F
authors.initials: EF
authors.lastname: Meydrech
authors.forename: P N
authors.initials: PN
authors.lastname: Neglen
mesh_terms: D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology; D001808:Blood Vessels / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009068:Movement / Q000502:physiology; D014159:Transducers; D014655:Vascular Resistance / Q000502:physiology*