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

Objectives: to explore the hydrodynamic mechanisms involved in the regulati on of ambulatory venous pressure. Design: air experimental model of calf venous pump was constructed with col lapsible tubes and valves. Material: the model consisted of a conduit and a pump with an intervening c ompetent valve. Another valve that could allow reflux into the pump was mou nted above the pump. Methods: conduit pressure and recovery times were monitored under condition s of different degrees of ejection fraction and reflux into the pump.Model variables included using poorly compliant tribes for the pump, the conduit and for both the pump and conduit. Results: the Index tube exhibited a non-linear volume-pressure relationship and a bi-modal regimen of compliance. This bestowed pressure-buffering pro perties. Ambulatory venous hypertension resulted when reflux beyond bufferi ng capacity occurred. Substituting less compliant PTFE for lates at the pum p had a relatively minor effect on post-ejection pressure and recovery time s. Using PTFE at the conduit had a profound but divergent effect on both of these parameters. Conduit capactiance reduction tmd a similar effect. Conclusion: conduit elastance plays a significant role in the regulation of ambulatory venous pressure in this experimental model. The hydrodynamic pr inciples illustrated by the model may enhance our understanding of the huma n calf venous pump.