Studies in calf venous pump function utilizing a two-valve experimental model.
OBJECTIVE
to explore the hydrodynamic mechanisms involved in the regulation of ambulatory venous pressure.


METHODS
an experimental model of calf venous pump was constructed with collapsible tubes and valves.


METHODS
the model consisted of a conduit and a pump with an intervening competent valve. Another valve that could allow reflux into the pump was mounted above the pump.


METHODS
conduit pressure and recovery times were monitored under conditions of different degrees of ejection fraction and reflux into the pump. Model variables included using poorly compliant tubes for the pump, the conduit and for both the pump and conduit.


RESULTS
the latex tube exhibited a non-linear volume-pressure relationship and a bi-modal regimen of compliance. This bestowed pressure-buffering properties. Ambulatory venous hypertension resulted when reflux beyond buffering capacity occurred. Substituting less compliant PTFE for latex at the pump had a relatively minor effect on post-ejection pressure and recovery times. Using PTFE at the conduit had a profound but divergent effect on both of these parameters. Conduit capacitance reduction had a similar effect.


CONCLUSIONS
conduit elastance plays a significant role in the regulation of ambulatory venous pressure in this experimental model. The hydrodynamic principles illustrated by the model may enhance our understanding of the human calf venous pump.
Raju
S
S
Department of Surgery, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505, USA.
Hudson
C A
CA
Fredericks
R
R
Neglén
P
P
Greene
A B
AB
Meydrech
E F
EF
D001795:Blood Pressure Determination / Q000295:instrumentation*; D006801:Humans; D006874:Hydrostatic Pressure; D007840:Latex; D007866:Leg / Q000098:blood supply*; D008955:Models, Cardiovascular; D011138:Polytetrafluoroethylene; D014690:Venous Pressure
D007840:Latex; D011138:Polytetrafluoroethylene