EXPERIMENTAL PLATFORM SIMULATING THE MECHANICAL EFFECTS OF DIAPHRAGMATIC MOTION ON INFERIOR VENA CAVA COLLAPSIBILITY

Open Access
Author:
Crompton, Philip Edward
Area of Honors:
Biomedical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Keefe B Manning, Thesis Supervisor
  • Justin Lee Brown, Honors Advisor
Keywords:
  • IVC filter
  • IVC collapse
  • diaphragmatic motion
  • inferior vena cava
Abstract:
Recurrent pulmonary embolism (PE) is common with an annual 300,000-600,000 cases in the United States and is often preventatively treated with inferior vena cava (IVC) filters when patients are ineligible for anticoagulant therapy. IVC filters have been plagued with issues, including fracture and migration of filter parts, puncture of the vessel wall, and further thrombogenesis, all of which are intuitively impacted by filter hemodynamics. While several experimental and computational studies have been performed on filter hemodynamics, none of taken into account the effects of diaphragmatic compression during breathing on the IVC. The goal of this study is to simulate the dynamic effects of diaphragmatic motion on IVC collapse experimentally, with validation provided through a computational model. To this end, a silicone model of typical IVC dimensions between the renal and iliac veins was placed in an acrylic chamber. A rigid track carrying a roller was placed on this chamber. Two stepper motors enabled the roller move in two dimensions, both compressing the vessel to an appropriate IVC collapsibility index (cIVC) and moving along its length for an appropriate total diaphragmatic excursion (TDE). Four conditions analogous to rest (2.0 lpm, 12 breaths/min, 15 % cIVC), light exercise (4.3 lpm, 16 breaths/min, 40% cIVC), heavy exercise (6.5 lpm, 20 breaths/min, 75% cIVC), and Valsalva maneuver (2.0 lpm, stationary, 30% cIVC) were tested. Additionally, a computational study was performed on a straight section of IVC with a stationary “roller” centered at a single point under the same conditions. IVC elliptical cross-section axes were measured for five data sets at each condition to ensure repeatability and major axis strain values calculated under minor axis compression in both experimental and computational results. Similar trends and low percent differences were found between the experimental and computational data, suggesting partial validation of the experimental platform and supporting its ability to reproduce in vivo IVC geometric deformations for future studies of IVC filter performance and hemodynamics.