Slit-Structured Cannula for Reliable Mechanical Thrombus Removal
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Solution Overview
Problem
Existing thrombus removal devices face challenges in effectively capturing and extracting large clots due to reliance on vacuum force, which can lead to clot release back into the blood vessel during extraction, and lack of flexibility and sealing capabilities for varying device sizes.
Innovation Solution
A flexible cannula with slits and a meltable outer jacket, combined with a distal removal element and adjustable seal valve, enhances clot capture and extraction by allowing bending and sealing around varying diameters, and a dual sheath system for large obstructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid cannula is used to maintain structural integrity, then the cannula can withstand vacuum forces, but the cannula cannot bend to navigate vascular pathways
Solution Approach 1:
The cannula is divided into multiple segments or sections that can flex relative to each other, allowing the cannula to bend while maintaining overall structural integrity. The segments are connected in a way that permits angular movement between them.
Solution Approach 2:
The cannula incorporates flexible materials and thin-walled structures that allow bending and deformation while maintaining sufficient strength to withstand vacuum forces. The wall thickness is optimized to balance flexibility and structural integrity.
2Device complexity
If vacuum force alone is used to capture thrombus, then the device structure is simple, but large clots cannot be captured and may be released back into the vessel
Solution Approach 1:
The cannula is pre-shaped or pre-formed with a specific geometry that facilitates clot capture before vacuum is applied. The cannula may have pre-formed hooks, loops, or expanded sections that engage the clot prior to aspiration.
Solution Approach 2:
The cannula incorporates curved or expanded sections that conform to the clot shape, allowing better engagement and capture. The curved geometry helps trap the clot within the cannula lumen and prevents it from slipping back during extraction.
3Reliability
If the cannula wall is made thick to maintain vacuum, then vacuum integrity is maintained, but the cannula flexibility and ability to navigate vessels is reduced
Solution Approach 1:
The cannula wall thickness is varied along its length, with thicker sections at the proximal end for vacuum integrity and thinner sections at the distal end for flexibility and navigability. Different segments have different wall thicknesses optimized for their specific functions.
Solution Approach 2:
The cannula is constructed from composite materials that combine high strength-to-weight ratio properties, allowing thin walls that maintain vacuum integrity while providing sufficient flexibility. The composite structure may include reinforcement layers or specialized polymer compositions.
4Adaptability or versatility
If the cannula is made flexible to navigate vessels, then the cannula can access target sites, but the cannula cannot maintain vacuum integrity for large clot capture
Solution Approach 1:
The cannula is divided into flexible distal segments for navigation and a stiffer proximal segment for vacuum integrity. The segmentation allows each section to be optimized for its specific function while working together as a unified structure.
Solution Approach 2:
The cannula uses composite material construction with varying material properties along its length, providing flexibility where needed while maintaining vacuum integrity in the proximal section. The composite structure allows simultaneous achievement of both flexibility and strength.
5Device complexity
If a single-diameter cannula is used, then the device is simple, but it cannot accommodate varying therapeutic tool sizes
Solution Approach 1:
The cannula incorporates an adjustable or deformable section that can change its internal diameter or cross-sectional area to accommodate different therapeutic tool sizes. The dynamic adjustment may be achieved through expandable sections, adjustable walls, or deformable membranes.
Solution Approach 2:
The cannula's internal dimensions are made variable rather than fixed, allowing the internal diameter to be adjusted based on the therapeutic tool being used. This parameter change enables a single cannula design to accommodate multiple tool sizes.
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 device improves thrombus removal by ensuring complete extraction without vessel blockage, maintaining vacuum, and accommodating diverse therapeutic tools, while increasing flexibility and sealing efficacy.
Implementation Method 1
the slits enabling the internal tube to bend in any direction by expansion and compression of the slits
Implementation Method 2
the outer jacket is made of a meltable polymer, and the discrete portions of the outer jacket include melted portions that stick to an outside of the inner tube
Implementation Method 3
A negative pressure (vacuum) is generated at the proximal side of the cannula typically using a vacuum syringe, causing the obstruction to be aspirated into the syringe through the cannula
Data Source
AI summary
A medical device includes a flexible cannula that includes an internal tube having a proximal end and a distal end and a series of slits cut along a length thereof between the proximal and the distal ends, and an outer jacket softer than the inner tube. Discrete portions of the outer tube are connected to the inner tube along a longitudinal axis of the cannula. Areas at which there is no connection between the outer jacket and the inner tube allow some relative movement between the outer jacket and the inner tube, resulting in increased flexibility of the cannula.