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: air 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 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 properties. Ambulatory venous hypertension resulted when reflux beyond buffering capacity occurred. Substituting less compliant PTFE for lates 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 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 principles illustrated by the model may enhance our understanding of the human calf venous pump.