Studies in calf venous pump function utilizing a two-valve experimental model.

OBJECTIVES

to explore the hydrodynamic mechanisms involved in the regulation of ambulatory venous pressure.

DESIGN

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

MATERIAL

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.

CONCLUSION

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.