Introducer Sheath with Encapsulated Reinforcing Coil
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Solution Overview
Problem
Introducer sheaths used to deliver medical devices to bodily passageways often kink when traversing tortuous pathways, especially in smaller vessels, due to insufficient flexibility and thin-wall construction, which reduces their effectiveness and limits access to target sites.
Innovation Solution
A flexible introducer sheath is formed with a thin-walled inner liner of fluoropolymer, a reinforcing coil, and an outer jacket of heat-formable material, where the coil is encapsulated within the bonded inner and outer polymeric layers to enhance kink resistance and maintain a low cross-sectional profile, and the sheath has varying stiffness along its length for improved trackability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the sheath is formed with thin-wall construction to enable entry into narrow vessels, then the ability to enter narrow vessels is improved, but the sheath exhibits increased propensity to kink and reduced trackability
Solution Approach 1:
The sheath combines multiple materials with different properties: an inner liner (fluoropolymer) for low friction, a reinforcing member (coil) for kink resistance, and an outer jacket (heat-formable material) for structural support. This composite structure allows the sheath to maintain thin walls for narrow vessel access while incorporating discrete reinforcement elements to prevent kinking.
Solution Approach 2:
The reinforcing member is positioned specifically within the sheath wall structure, providing localized reinforcement only where needed for kink resistance. The inner liner and outer jacket maintain their respective functions (lubrication and structural integrity) without being uniformly thickened, allowing the sheath to remain flexible and suitable for narrow vessels while resisting kinks at critical locations.
2Reliability
If the sheath wall thickness is increased to improve kink resistance and trackability, then the level of kink resistance is improved, but the ability to enter narrow vessels is limited and the lumen diameter is reduced
Solution Approach 1:
Instead of uniformly increasing wall thickness, the invention uses a composite structure with an inner liner, reinforcing member, and outer jacket. This allows the sheath to achieve enhanced kink resistance through the reinforcing member and outer jacket while keeping the overall wall construction efficient and the outer diameter minimized for narrow vessel access.
Solution Approach 2:
The sheath wall is segmented into distinct functional layers: the inner liner for lubrication, the reinforcing member for kink resistance, and the outer jacket for structural support. This segmentation allows each layer to be optimized for its specific function without requiring uniform thickening of the entire wall, thereby maintaining a smaller outer diameter.
3Ease of operation
If the sheath is made more flexible at the distal end to enable proper positioning in tortuous pathways, then the flexibility for positioning is improved, but the trackability through tortuous areas is reduced
Solution Approach 1:
The sheath is constructed with varying properties along its length, with the distal end having greater flexibility for navigation and positioning while the proximal end maintains sufficient stiffness for trackability and support. The reinforcing member and jacket construction can be varied axially to achieve this gradient, allowing the distal portion to conform to tortuous anatomy while the proximal portion provides stability.
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 sheath effectively navigates tortuous anatomy without kinking, maintaining a low profile and allowing access to previously difficult-to-reach areas while ensuring secure bonding and minimal increase in outer diameter.
Implementation Method 1
The heat-formable material is heat shrunk onto the PTFE outer surface by enveloping it in a heat shrink tube, and heating the entire assembly until the material melts
Implementation Method 2
heating the entire assembly until the material melts. As the heat-formable material melts, it flows between the spacings of the coil turns, and bonds to the outer diameter of the PTFE layer
Data Source
Figure 1~2
Figure 3
AI summary
An introducer sheath. (10) and a method for making the sheath. The sheath includes a f luoropolymer liner (31) having a passageway extending longitudinally therethrough. An inner jacket (35) is positioned longitudinally over the liner, and the inner surface of the inner jacket is bonded to the outer surface of the liner. An outer jacket (44) is positioned longitudinally over the inner jacket, and the inner surface of the outer jacket is bonded to the outer surface of the inner jacket. A reinforcing coil (40) is encapsulated within the inner jacket and the outer jacket.