Stylet for Percutaneous Catheter Radial Contraction
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Solution Overview
Problem
Conventional percutaneous cardiopulmonary support systems face challenges in minimizing the degree of invasion and pressure loss in extracorporeal circulation tubes, where small inner diameters increase pressure loss and flow rate decreases, while larger diameters increase the burden on the patient.
Innovation Solution
A stylet with an expandable expansion portion and a shaft portion that can extend axially, featuring an outer peripheral member with a matching inner diameter and an inner peripheral member that slides without friction, allowing the expansion portion to contract radially inward for minimally invasive insertion and expand post-insertion to reduce pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inner diameter of the catheter tube is increased to reduce pressure loss and increase blood flow rate, then the pressure loss decreases and blood flow rate increases, but the outer diameter increases which increases the degree of invasion on the patient's body
Solution Approach 1:
The catheter tube employs a dynamic structure where the expansion portion can change its radial dimension. During insertion, the expansion portion is contracted radially inward to minimize outer diameter and patient burden. After insertion, the expansion portion expands radially outward to increase inner diameter, reducing pressure loss and increasing blood flow rate. This dynamic transformation allows the catheter to adapt its dimensions to different operational phases.
Solution Approach 2:
The stylet is inserted into the catheter tube to mechanically control the expansion portion. The stylet's outer peripheral member fits within the shaft portion's inner diameter, and the inner peripheral member slides within the outer peripheral member's inner passage. This nested arrangement allows the stylet to transmit axial force to the expansion portion, enabling radial contraction during insertion and radial expansion after insertion, thus resolving the contradiction between minimized invasion and maximized flow capacity.
2Volume of moving object
If the shaft portion contracts radially inward during stylet insertion, then the catheter becomes more compact, but frictional resistance with the stylet increases preventing full insertion and complete contraction of the expansion portion
Solution Approach 1:
The stylet is divided into two distinct members: an outer peripheral member and an inner peripheral member. The outer peripheral member has an outer diameter matching the shaft portion's inner diameter, while the inner peripheral member slides within the outer peripheral member's inner passage. This segmentation allows the outer peripheral member to contact the shaft portion for radial contraction, while the inner peripheral member provides a low-friction sliding surface, preventing excessive friction and enabling complete stylet insertion and expansion portion contraction.
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 stylet enables minimally invasive insertion with reduced pressure loss and increased blood flow rate by allowing the expansion portion to contract radially inward during insertion and expand post-insertion, thereby minimizing patient burden and ensuring sufficient blood circulation.
Implementation Method 1
an inner passage defined by an inner periphery of the outer peripheral member in which the inner peripheral member is received, the inner peripheral member is slidable without frictional resistance
Data Source
AI summary
A catheter system insertable into a living body to convey blood has a catheter tube and a stylet. The catheter tube has an expansion portion, a shaft portion, and a lumen. The stylet includes an outer peripheral member that extends in an axial direction and has an outer diameter the same as an inner diameter of the shaft portion, an inner peripheral member provided with an exposed portion exposed from a distal end of the outer peripheral member and provided on an inner periphery of the outer peripheral member so as to be slidable with respect to the outer peripheral member, and a fitting stopper into which a fitting member on an outer periphery of a proximal end of the outer peripheral member is fittable. A region is formed in the fitting stopper in which the outer peripheral member and the fitting member are movable.