Nested Catheter Assembly Reducing Outer Diameter and Kinking
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Solution Overview
Problem
Catheters with reduced thickness face challenges such as collapse, kinking, and difficulty in navigating bent blood vessels due to decreased strength, which can lead to tissue damage and increased resistance during insertion.
Innovation Solution
A catheter assembly featuring a shaft with an accommodation unit that decreases the outer diameter of the catheter's distal end, allowing it to be accommodated within the shaft, reducing tissue contact and enabling easier navigation through blood vessels while maintaining sufficient strength and minimizing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the catheter body thickness is decreased to reduce outer diameter for insertion into narrow blood vessels, then the catheter can be inserted into narrower vessels, but the catheter body strength is degraded causing collapse and kinking
Solution Approach 1:
The invention employs a nested structure where an inner catheter is inserted into an outer catheter. The inner catheter has a larger outer diameter than the outer catheter's inner diameter, creating a tight fit that provides structural support. This nested configuration allows the outer catheter to maintain a small outer diameter for vessel insertion while the inner catheter prevents collapse and kinking through its stiffer structure.
2Volume of moving object
If the catheter body thickness is decreased to reduce outer diameter, then the catheter can be inserted into narrow blood vessels, but the pushing performance is degraded making it difficult to thrust forward
Solution Approach 1:
The nested dual-catheter structure enables force transmission improvement. The inner catheter, being stiffer due to its larger diameter-to-thickness ratio, serves as a force transmission element that can effectively transmit pushing forces from the proximal end to the distal end. This allows operators to thrust the catheter assembly forward through bent or resistant vessel segments despite the outer catheter's thin construction.
3Volume of moving object
If the catheter body thickness is decreased to reduce outer diameter, then the catheter can be inserted into narrow blood vessels, but the distal portion becomes sharp causing damage to biological tissue
Solution Approach 1:
The nested configuration addresses the sharp distal end problem through geometric compensation. The inner catheter's larger outer diameter creates a stepped or tapered transition at the distal end, preventing the outer catheter's thin wall from forming a sharp point. This structural arrangement maintains tissue compatibility while preserving the outer catheter's small overall diameter for vessel access.
4Force
If a shaft is inserted into an outer catheter to prevent collapse and kinking, then the pushing performance is improved, but a step difference is formed at the distal portion causing tissue damage or turning inside out
Solution Approach 1:
The invention applies local quality modification at the distal end of the inner catheter. The distal end portion is designed with a smaller outer diameter than the main body, creating a smooth tapered transition that eliminates the step difference between inner and outer catheters. This localized geometric adjustment maintains the stiff force-transmitting structure in the proximal portion while ensuring tissue compatibility at the distal tip.
Solution Approach 2:
The solution addresses the step difference problem by introducing dimensional variation along the axial dimension. The inner catheter's distal end is tapered or reduced in diameter, creating a gradual transition in the radial dimension that smooths the interface with the outer catheter. This dimensional change eliminates the abrupt step that would otherwise cause tissue damage or catheter inversion during insertion.
Data Source
AI summary
A catheter assembly includes an outer catheter and an inner catheter. The inner catheter has an accommodation unit which can be positioned on a farther distal side than an outer catheter body in a state where an inner catheter body is inserted into the outer catheter body, extends in a proximal direction from the inner catheter body, and can accommodate an outer catheter distal portion so as to surround an outer circumference thereof in a state where the outer catheter distal portion formed at a distal end of the outer catheter body is reduced in diameter. The outer catheter distal portion can be separated from the accommodation unit and can expand in diameter by moving the inner catheter body in a distal end direction relatively with respect to the outer catheter body from a state of being accommodated in the accommodation unit.