Dialysis Valve Using Nitinol Superelasticity to Control Blood Flow
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dialysis grafts often experience intimal hyperplasia and premature clotting due to high blood flow rates during dialysis, leading to graft occlusion, as flows above 300 cc per minute cause stenosis and thrombosis, while lower flows indicate impending thrombosis.
Innovation Solution
A dialysis valve with a braided nitinol structure capable of altering its diameter and length to control blood flow, using a bellows, balloon, or nitinol spring mechanism to manage fluid dynamics and prevent excessive blood flow between dialysis sessions, maintaining fluid containment and biocompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high blood flow rates (>300 cc/min) are maintained through the dialysis graft, then sufficient blood flow for successful dialysis runs is achieved, but intimal hyperplasia and stenosis occur in the outflow vein leading to graft occlusion
Solution Approach 1:
The patent applies a dynamic flow control mechanism that adjusts the graft lumen diameter based on dialysis session status. During dialysis, the graft maintains a larger diameter to allow high blood flow rates (>300 cc/min) necessary for successful treatment. Between sessions, the graft automatically constricts to a smaller diameter to reduce blood flow to below 300 cc/min, preventing intimalhyperplasia and stenosis in the outflow vein. This dynamic adaptation resolves the contradiction by making the blood flow rate variable rather than fixed.
2Object-affected harmful factors
If low blood flow rates (<300 cc/min) are maintained through the dialysis graft, then intimalhyperplasia and stenosis are prevented, but graft thrombosis occurs
Solution Approach 1:
The patent implements periodic flow rate modulation that alternates between high flow during dialysis sessions and low flow during inter-dialysis periods. The flow control mechanism is activated periodically to constrict the graft between sessions, reducing flow to prevent intimalhyperplasia while maintaining sufficient flow during actual dialysis to prevent thrombosis. This periodic action pattern ensures both protective effects and adequate perfusion at different times.
3Object-affected harmful factors
If the graft lumen is constricted to reduce blood flow, then intimalhyperplasia is prevented, but the graft cannot provide sufficient flow during dialysis
Solution Approach 1:
The flow control mechanism dynamically adjusts lumen diameter based on real-time or predetermined dialysis session status. During active dialysis, the mechanism opens the graft to allow high flow rates necessary for successful treatment. Between sessions, it automatically constricts to reduce flow and prevent stenosis. This dynamic response ensures the graft provides appropriate flow characteristics for each operational phase without manual intervention.
4Object-affected harmful factors
If a flow control mechanism is added to the dialysis graft, then blood flow can be regulated to prevent complications, but device complexity increases
Solution Approach 1:
The flow control mechanism is designed to operate autonomously without requiring external power sources, control systems, or manual operation. The valve or constriction device responds automatically to predefined triggers such as dialysis machine connection status or pressure differentials, self-regulating the graft flow based on operational conditions. This self-service capability reduces complexity by eliminating the need for complex control electronics, power supplies, or external actuation systems.
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 controlled blood flow reduces the risk of intimal hyperplasia and thrombosis by limiting arterial pressure, maintaining vascular access, and preventing graft occlusion, while allowing sufficient flow during dialysis, thus extending graft lifespan.
Implementation Method 1
when the bellows increases in length, the tube simultaneously increases in longitudinal dimension and at least a portion of the tube decreases in diameter
Implementation Method 2
A nitinol structure processed to exhibit superelasticity below normal human body temperature
Implementation Method 3
A balloon contacts the tube so that when the balloon is inflated at least a portion of the tube decreases in diameter
Data Source
AI summary
A dialysis valve includes a tube attached between an artery and a vein which, when elongated, simultaneously narrows in diameter at at least one location. The narrowed portion of the tube decreases the volume and velocity between the arterial and venous side of the patient to prevent damage or intimal hyperplasia on the venous side between dialysis treatments. When the valve is opened for dialysis, an unrestricted blood flow exists between the arterial and venous side, permitting a controlled, open blood flow during dialysis.