Compressed Elastomeric AV Graft Structure for Puncture Sealing
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Solution Overview
Problem
Existing grafts for arteriovenous access suffer from significant fluid leakage at puncture sites after needle removal, despite the use of laminates with self-sealing materials.
Innovation Solution
A three-layer graft construction comprising an inner ePTFE layer, a middle self-sealing elastomeric layer under circumferential compression, and an outer ePTFE layer, with the elastomeric layer being compressed circumferentially to enhance sealing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laminate of graft material and elastomeric material is used, then self-sealing capability is improved, but fluid leakage at puncture sites persists
Solution Approach 1:
The patent applies parameter changes by subjecting the elastomeric material layer to circumferential compression, transforming its mechanical state to enhance sealing. The compression modifies the material's physical parameters (stress state, density) to enable effective puncture sealing while maintaining the laminate structure's self-sealing capability.
Solution Approach 2:
The patent utilizes composite materials by creating a laminate structure combining graft material (ePTFE) and elastomeric material (silicone or fluoroelastomer). This composite construction leverages the complementary properties of each material: the graft material provides structural integrity and puncture resistance, while the elastomeric material provides elasticity and sealing capability, together resolving the fluid leakage problem.
2Reliability
If the elastomeric layer is compressed circumferentially, then sealing effectiveness is improved, but graft wall thickness increases
Solution Approach 1:
The patent applies local quality by implementing circumferential compression specifically in the elastomeric material layer while maintaining the graft material layers at their original thickness. This localized compression enhances sealing effectiveness at the puncture site without requiring increased overall graft wall thickness, as the compression is confined to the specific functional layer needed for sealing.
3Reliability
If a three-layer laminate structure is used, then leak resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the graft wall into three distinct functional layers: an inner graft material layer, a middle elastomeric material layer, and an outer graft material layer. Each layer is manufactured separately with specific properties optimized for its function, then assembled into the complete laminate structure. This segmentation enables complex functionality (leak resistance through multiple sealing mechanisms) while maintaining manageable manufacturing complexity through modular construction.
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 graft significantly reduces fluid leakage at puncture sites by utilizing residual compressive stresses in the elastomeric layer, allowing for a thinner graft design with effective leak resistance and compatibility with delivery systems.
Implementation Method 1
the tubular form of the three-layer graft is everted to put substantially the entire wall thickness of the elastomeric material layer under circumferential compression
Implementation Method 2
utilizing residual compressive stresses in the elastomeric layer
Data Source
AI summary
Implantable grafts, particularly for arteriovenous access that may be punctured by an object such as a needle and, following removal of the object, will reseal the resulting hole to the extent of reducing fluid leakage through the graft at the puncture site to an amount less than would be typical for a conventional graft. More particularly, the grafts comprise three layers; an inner layer of implantable graft material such as ePTFE, a middle layer of self sealing elastomeric material such as silicone, and an outer layer of implantable graft material such as ePTFE. Following manufacture, the tubular form of the three-layer graft is everted to put substantially the entire wall thickness of the elastomeric material layer under circumferential compression.