The Design and Validation of a Dynamic Arteriovenous System Valve Mechanism

Master thesis (2021)

Authors

N.A. White Mechanical Engineering

Contributors

T. Horeman Medical Instruments & Bio-Inspired Technology - Mechanical, Maritime and Materials Engineering (supervisor 1)
Joris Rotmans Leiden University Medical Center (supervisor 2)
Faculty
Mechanical Engineering
Copyright: © 2021 Nick White
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Published Date

19-02-2021

Language

English

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Faculty

Mechanical Engineering

Abstract

Background: Patients suffering from end-stage renal disease (ESRD) often require haemodialysis to filter the blood of waste products. Currently, an arteriovenous fistula (AVF) or graft (AVG) is used in most cases to enable sufficient blood flow for haemodialysis, but these have been associated with a large number of undesirable patient outcomes. Most of these can be linked to the resulting constant high blood-flow and the anastomosis remaining in an open position. To counter this, an implantable Dynamic Arteriovenous System (DAS) that can regulate blood flow through an anastomosis is to be developed. For this, a valve mechanism is to be designed and validated, that converts a mechanical translation from an actuator into an opening and closing motion on a synthetic graft.
Objective: The goal of this research is to design a proof-of-concept DAS valve mechanism, and validate this ex vivo.
Method: A methodological approach was utilised to generate concepts for a DAS valve that can fully collapse and open a synthetic graft acting as anastomosis. A Harris profile with a set of grading criteria is set up to determine the optimal concept. This concept is assessed through means of a number of test setups, that includes force measurement during collapse and opening of the graft, traction, and lifetime.
Results: The result of the design study is a linkage mechanism utilising pinhole joints that converts the input into an (approximately) vertical translation on the top and bottom of the graft. A transmission ratio that approaches infinity when the graft is fully
collapsed is achieved, whilst allowing an infinite number of states to control flow when open. The majority of the requirements set are met, but the necessary input force, traction andmass require some optimisation to fulfil the criteria.
Conclusion: From this study it was concluded that the current design shows promise but a next design iteration is necessary to fully meet all design criteria. Future research should include the transmission of the actuator input to the valve and the assessment of foreign body response, which may require the development of a sealing method.