Degree Candidacy: Master of Science in Mechanical Engineering
Date: Thursday, July 17, 2014
Time: 10:00 AM
Location: 132 EIB
Advisor: Dr. Richard Figliola
Committee Members: Dr. Donald Beasley and Dr. Naren Vyavahare
Title: Development of an In Vitro System for Evaluation of Prosthetic Vein Valves
Chronic venous insufficiency is a chronic disorder where venous pressure is not reduced during exercise. In a healthy individual, the vein valves and muscle pumps of the extremities combine to allow for a reduction in venous pressure during exercise. Consistent high pressure in the leg can lead to disability, pain, and ulcer formation. Typical causes of chronic venous insufficiency are venous reflux and acute venous obstruction. Research is under way to develop a prosthetic vein valve that can easily be implanted with a minimally invasive catheter procedure which addresses chronic venous insufficiency. This thesis discusses development of an in vitro test system in order to evaluate new prosthetic venous valves.
A lumped parameter model of the leg venous system is developed which can simulate venous pressure and flow during calf muscle action while standing. A table top representation of the lumped parameter model is constructed, and the system is tuned to have a physiological ankle pressure response during exercise. The effects of an ideal venous valve, a missing or incompetent venous valve, and an acute thrombosis are all used as baseline conditions to ensure a physiological response. During tuning, system parameters are adjusted in order to match physiological ambulatory venous pressures and pressure recovery times.
After the system has been tuned to have an accurate pressure response, based for all baseline test sections, ambulatory venous pressure and flow rate through each test section is in a physiological range. This is the first time physiological pressure response has been modeled for patients with chronic venous insufficiency, both due to high reflux and acute thrombosis. High reflux flow rate in the biological test section paired with an ambulatory venous pressure in the range sufficient to reduce risk of venous ulceration suggests that reflux flow rate may be an inappropriate parameter for in vitro evaluation of prosthetic valves when not paired with simulation of physiological pressure response.