Hydraulic Catheter Actuator for Stent Deployment
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Solution Overview
Problem
Conventional self-expanding stent delivery systems require high force for sheath retraction, leading to potential incorrect placement and increased risk of stent migration due to full-length sheath design and static friction, making them inefficient and difficult to use, especially for longer stents.
Innovation Solution
A hydraulic delivery system with a catheter design featuring a movable outer tubular member and pressure chamber, utilizing fluid pressure to retract the sheath efficiently, reducing the force required for stent deployment and minimizing the risk of stent migration by limiting sheath extension to the distal end, and incorporating features like expandable seals and a spring mechanism for enhanced retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the outer sheath spans the full length of the catheter to prevent stent migration, then stent placement accuracy is improved, but the force required to retract the sheath increases substantially
Solution Approach 1:
The catheter is divided into distinct segments: a full-length outer sheath for migration prevention and a distal pressure chamber for localized actuation. The retraction force is applied locally at the distal end rather than along the entire length, reducing the total force required while maintaining the sheath's migration-preventing function throughout its length.
Solution Approach 2:
A pressure chamber is positioned at the distal end of the outer sheath, in fluid communication with the inner tubular member. Hydraulic or pneumatic pressure applied to the inner member transfers force to the distal end of the outer sheath, enabling controlled retraction with reduced input force compared to direct manual retraction of the entire sheath length.
2Ease of operation
If the outer sheath is pulled back in a 1-to-1 ratio with user input force, then operational simplicity is maintained, but large initial input force is required to overcome static friction and stent embedding
Solution Approach 1:
The pressure chamber system provides mechanical advantage through fluid pressure multiplication. A relatively small pressure applied to the inner tubular member generates sufficient force at the distal end of the outer sheath to overcome static friction and stent embedding, reducing the initial input force requirement while maintaining controlled retraction.
Solution Approach 2:
The system changes the force application parameter from direct linear pull (1-to-1 ratio) to pressurized fluid actuation. This parameter change allows for controlled force delivery that can overcome high static friction without requiring proportionally high user input force, enabling smoother initial retraction.
3Reliability
If a full-length outer sheath is used to constrain the stent, then stent migration is prevented, but the catheter profile and stiffness increase over the entire length
Solution Approach 1:
The catheter structure is segmented into a full-length outer sheath for migration prevention and a localized distal pressure chamber for actuation. This segmentation allows the sheath to maintain its migration-preventing function throughout its length while concentrating the active retraction mechanism at the distal end, optimizing the profile without sacrificing reliability.
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 hydraulic delivery system reduces the force needed for stent deployment, enhances precision in placement, and minimizes the risk of stent migration by using fluid pressure to retract the sheath efficiently, improving the overall efficiency and accuracy of stent delivery.
Implementation Method 1
A pressure chamber is defined by the proximal seal, the distal seal, the exterior surface of the inner tubular member and the interior surface of the outer tubular member, with the pressure chamber in fluid communication with the fluid flow port, wherein fluid introduced through the fluid flow port and into the pressure chamber applies a force on the proximal seal to urge the outer tubular member in a proximal direction.
Data Source
AI summary
Catheter for delivery of a medical device such as a stent or filter includes an inner tubular member and an outer tubular member movable relative to the inner tubular member. The outer tubular member is disposed at the distal end of the inner tubular member. The inner tubular member includes a fluid lumen defined therein, the fluid lumen having a fluid flow port directed to the exterior surface of the inner tubular member. A pressure chamber is defined by the inner tubular member, the outer tubular member, a proximal seal and a distal seal, and is in fluid communication with the fluid flow port, wherein fluid introduced through the fluid flow port and into the pressure chamber applies a force on the proximal seal to move the outer tubular member in a proximal direction allowing the medical device constrained by the outer tubular member to be released.