Flexible Catheter Minimizes Tip Displacement During Chorionic Villus Sampling

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Solution Overview

Problem

Existing catheters for chorionic villus sampling face issues with tip displacement and membrane rupture due to the stiffness of the obturator, which affects precision and safety during the procedure.

Innovation Solution

A catheter design featuring a flexible plastic cannula and a flexible stainless steel obturator with a molded handle and steering guide for improved manipulation and placement, allowing for precise guidance and minimizing tip displacement upon withdrawal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a stiff obturator is used to maintain cannula support during insertion, then the cannula can be inserted easily, but the cannula tip deflects from the desired location when the obturator is withdrawn

Engineering Contradiction:

Improveease of insertionVSAvoidcannula tip position accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent changes the material parameter of the obturator from stiff (aluminum, stainless steel) to flexible (polymer, rubber), which allows the obturator to conform to the cannula shape during insertion but not cause deflection when removed. This parameter change resolves the contradiction between ease of insertion and tip position accuracy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite structure where a flexible obturator is placed within a flexible cannula. The flexible obturator provides support during insertion while the flexible cannula maintains its shape without deflection when the obturator is removed, resolving the contradiction between insertion ease and tip position precision.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If a stiff catheter is used to prevent cannula deflection, then tip position is maintained, but the catheter causes ruptures in patients' membranes

Engineering Contradiction:

Improvecannula tip position accuracyVSAvoidmembrane rupture risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the rigidity parameter of the entire catheter assembly by using flexible materials for both the cannula and obturator. This reduces the overall stiffness to a level that prevents membrane rupture while still maintaining sufficient support during insertion and accurate tip positioning.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs flexible materials (polymer, rubber) for the obturator and cannula, allowing the catheter to bend and conform to anatomical structures without causing membrane rupture, while still providing adequate support for precise tip placement.

Inventive Principle:

Principle #30Flexible shells and thin films

3Measurement precision

If a flexible obturator is used to prevent cannula deflection, then tip position is maintained, but the obturator cannot provide sufficient support during insertion

Engineering Contradiction:

Improvecannula tip position accuracyVSAvoidease of insertion

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent optimizes the flexibility parameter of the obturator to a specific range that provides sufficient support during insertion while preventing deflection when removed. The flexible material is chosen to have enough rigidity to support the cannula during insertion but not enough to cause deflection upon withdrawal.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a flexible obturator that can dynamically adapt its support characteristics during the procedure - providing support when needed during insertion, then allowing the cannula to maintain its shape independently when the obturator is removed, thus resolving the contradiction between insertion ease and tip position accuracy.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8323209B2Chorionic villus sampling catheter

Publication Date: 2012.12.04 WILLIAMS III JOHN

AI summary

A catheter with a guide wire and handle is provided for sampling an area of interest, such as chorionic villi. The catheter contains a cannula of flexible plastic that is non-pyrogenic and latex-free, and a flexible obturator with an elongate cylindrical handle. The cannula is echogenic and can be easily visualized with visualization or imaging device. In an embodiment, the catheter may be curved manually by the operator to conform to the patient's anatomy and it is inserted through the cervix into a pregnant uterus at 10-13 weeks gestation and placed into the developing placenta under ultrasound guidance and a guide mechanism provided on the handle. In this embodiment, once the catheter has been placed, the obturator is withdrawn and a sample of chorionic villi is removed by applying appropriate pressure to the proximal end of the cannula and slowly withdrawing the cannula from the uterine cavity.