Subcutaneous Vascular Access Assembly Bypassing Occlusions
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Solution Overview
Problem
Patients undergoing hemodialysis often face challenges in accessing a stable blood supply, particularly when peripheral venous access sites are exhausted, and existing vascular access methods may not effectively bypass central venous stenosis or occlusions.
Innovation Solution
A vascular access assembly comprising a first tubular conduit and a second tubular conduit, along with an expandable stent graft, is implanted subcutaneously to create an artificial blood flow path that bypasses occlusions, using nitinol for resistance to kinking and crush forces, and PTFE for self-sealing properties, allowing for fluid communication and therapeutic agent delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vascular access methods are used, then initial access is simpler, but reliability deteriorates when peripheral venous access sites are exhausted or central venous stenosis is present
Solution Approach 1:
The vascular access device is divided into multiple segments: a first tubular conduit for initial placement, a second tubular conduit for later connection, and an expandable stent graft for permanent fixation. This segmentation allows the system to progress from temporary to permanent access, improving reliability while managing complexity through staged implementation.
Solution Approach 2:
The first tubular conduit is implanted preliminarily to establish initial vascular access before the second conduit and stent graft are deployed. This preliminary action provides immediate access while preparing the pathway for the more reliable permanent implant, resolving the contradiction by providing both immediate and long-term solutions.
2Ease of operation
If the conduit is made flexible for ease of implantation, then ease of operation improves, but resistance to kinking and crush forces deteriorates
Solution Approach 1:
Different sections of the conduit system have different mechanical properties optimized for their specific functions. The first tubular conduit is highly flexible for ease of implantation through tissue tunnels, while the expandable stent graft portion provides rigid structural support to prevent kinking and crush forces once deployed in the vascular system.
Solution Approach 2:
The device combines multiple materials with complementary properties: flexible polymer materials for the tubular conduits that enable easy implantation, and nitinol or other metal alloy materials for the expandable stent graft that provide kink and crush resistance. This composite construction resolves the contradiction by integrating both flexibility and strength in different components.
3Reliability
If the stent graft is expanded to provide stable fixation, then reliability improves, but device complexity increases due to expansion mechanism
Solution Approach 1:
The expandable stent graft is designed to self-expand upon deployment, utilizing the elastic recovery properties of the nitinol material. The graft transitions from a compressed delivery state to an expanded functional state through its own inherent mechanical properties, eliminating the need for complex external expansion mechanisms and reducing overall device complexity while maintaining fixation stability.
Solution Approach 2:
The stent graft utilizes phase transformation properties of nitinol material, changing from an austenite phase (rigid, expanded state) to a martensite phase (flexible, compressed state) during delivery and deployment. This parameter change enables the graft to be compressed for implantation and then automatically expand to provide stable fixation, resolving the contradiction between reliability and complexity.
4Ease of operation
If the conduit wall is made thin for flexibility, then ease of operation improves, but self-sealing capability deteriorates
Solution Approach 1:
The conduit system employs different wall thicknesses in different sections: thinner walls in the first tubular conduit for flexibility and ease of implantation, and thicker walls in the second conduit and stent graft portions where self-sealing capability is critical for maintaining vascular access and preventing leakage.
Solution Approach 2:
The conduit incorporates composite wall structures with multiple layers having different properties: an inner layer with self-sealing characteristics for leak prevention, and outer layers providing flexibility and structural support. This composite construction allows the conduit to simultaneously achieve flexibility for ease of operation and self-sealing capability for reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The assembly provides a reliable, self-sealing, and kink-resistant artificial blood flow path that effectively bypasses occlusions, maintaining fluid communication and facilitating hemodialysis even when natural access sites are compromised.
Implementation Method 1
an expandable stent graft configured to transition from a compressed state to a deployed state
Implementation Method 2
The tubular conduit may be made from Dacron, PTFE, polyethylene, polypropylene, silicone, or other biocompatible materials and may include an embedded nitinol mesh
Implementation Method 3
PTFE for self-sealing properties
Data Source
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AI summary
Vascular access devices, assemblies, kits, and related methods are disclosed. A vascular access assembly may include a first tubular conduit, a second tubular conduit, and an expandable stent graft that is coupled adjacent to a peripheral end of the second tubular conduit. When implanted into the patient, vascular access assemblies may form a flow path that extends from an artery or an arteriovenous graft to a heart of a patient. The vascular access assembly, when implanted and assembled, may be a fully subcutaneous surgical implant.