Introducer Sheath Distal Tip Curvature Stress Distribution
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Solution Overview
Problem
Existing introducer sheaths with thin wall thickness tend to curl upward when puncturing skin or blood vessels, lacking configurations that prevent this issue while maintaining a small outer diameter and large inner diameter for catheter insertion.
Innovation Solution
The introducer sheath features a distal portion with a tapering outer diameter, including a concave portion bent radially inward and a convex portion bent radially outward in a quadratic or parabolic curve shape, which decentralizes stress and prevents curling by forming an acute angle and providing sufficient thickness, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the wall thickness of the introducer sheath is made small to reduce outer diameter and increase inner diameter, then the ease of catheter insertion is improved, but the distal portion becomes prone to curling upward during puncture
Solution Approach 1:
The distal portion is designed with a curved external shape including a concave portion bent radially inward and a convex portion bent radially outward in quadratic or parabolic curve shapes. This curvature distributes stress along the curved surfaces during puncture, preventing the distal portion from curling upward while maintaining thin wall thickness for easy catheter insertion.
Solution Approach 2:
The outer diameter of the distal portion is tapered to be smaller than the main body portion, and the wall thickness is optimized to be thin (0.5-2.0 mm) to reduce overall diameter and facilitate catheter passage. These parameter changes enable easy insertion while the curved shape compensates for the reduced structural rigidity.
2Ease of operation
If the outer diameter of the introducer sheath is reduced to facilitate puncture, then the ease of puncture is improved, but the inner diameter available for catheter insertion is reduced
Solution Approach 1:
The wall thickness of the distal portion is made thin (0.5-2.0 mm) to maximize the inner diameter available for catheter insertion. This parameter change allows the introducer sheath to have a small outer diameter for easy puncture while maintaining a sufficiently large inner diameter for catheter passage.
Solution Approach 2:
The wall thickness is made thin specifically in the distal portion where it needs to be flexible and small for puncture, while the main body portion can have a larger diameter. This local quality differentiation allows the distal portion to be easily inserted while providing adequate space for catheters in the main body.
3Adaptability or versatility
If the wall thickness of the distal portion is made thin to allow elongated bodies with large outer diameters to be inserted, then the adaptability is improved, but the distal portion curls upward when puncturing
Solution Approach 1:
The curved external shape with concave and convex portions distributes the puncture stress along the curved surfaces, preventing the distal portion from curling upward. This allows the wall thickness to be made thin for adaptability to different catheter sizes while maintaining stability during puncture.
Solution Approach 2:
The curved shape is pre-formed in the distal portion before use, creating a stress-distributing geometry that prevents curling during the actual puncture operation. This preliminary structural preparation enables thin-walled construction without compromising puncture stability.
Data Source
AI summary
An introducer sheath is provided with a sheath tube which is formed of a tubular member provided with a hollow portion through which an elongated body is freely inserted and includes a distal portion having a tapering outer diameter and a main body portion having a constant outer diameter. The distal portion of the sheath tube includes a concave portion which is bent radially inward from an end portion, through which an elongated body protrudes, in a concave shape in a cross section parallel to an axial direction, and a convex portion which is contiguous to the concave portion and is bent radially outward in a convex shape in a cross section parallel to the axial direction.