Flexible-Bladder Windkessel Simulation for Reduced Air Infusion
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Solution Overview
Problem
Existing technologies fail to effectively simulate the Windkessel effect, which is crucial for maintaining physiological blood pressure and perfusion during extracorporeal heart perfusion, and often introduce unwanted air infusion into the coronary artery.
Innovation Solution
A Windkessel simulation apparatus comprising a flexible fluid container with a reactive squeezing mechanism that applies compressive pressure to mimic arterial compliance, connected to an ex vivo circulation system with a pulsatile pump and preload reservoir to manage fluid flow and pressure, reducing air infusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid container is used to deliver fluid to the heart, then fluid delivery is stable, but the Windkessel effect cannot be simulated and air infusion occurs
Solution Approach 1:
The patent employs a flexible bladder instead of a rigid container to deliver fluid to the heart. The bladder's elastic walls allow it to expand during filling and contract during emptying, simulating the Windkessel effect. This flexibility prevents air infusion while maintaining stable fluid delivery, as the compliant container absorbs pressure fluctuations and eliminates the need for high-pressure pulsatile pumping that would otherwise force air into the coronary arteries.
2Stability of the object's composition
If a pulsatile pump is used to deliver fluid, then blood pressure fluctuation is simulated, but air infusion into the coronary artery occurs
Solution Approach 1:
The patent introduces a flexible bladder as an intermediary between the pulsatile pump and the heart. The bladder absorbs the high-pressure pulsatile output from the pump and delivers a smoother, more physiological flow to the heart. This intermediary component transforms the pump's aggressive pulsatile flow into gentle pressure fluctuations that simulate natural blood pressure without forcing air into the coronary arteries.
3Adaptability or versatility
If a compliant container is used to simulate arterial compliance, then Windkessel effect is achieved, but device complexity increases
Solution Approach 1:
The patent employs a self-service mechanism where the flexible bladder's inherent elasticity provides the compliance needed to simulate arterial walls. The squeezing mechanism utilizes the bladder's own elastic recoil to drive fluid delivery, eliminating the need for complex external actuators or control systems. The system essentially uses the container's material properties to perform the compliance simulation function, reducing overall device complexity.
4Productivity
If high compressive pressure is applied to the flexible container, then fluid is driven toward the heart effectively, but the container may deform excessively
Solution Approach 1:
The patent employs a dynamic squeezing mechanism that adjusts compressive pressure throughout the cardiac cycle. During systole, higher compression drives fluid into the heart; during diastole, compression is reduced to allow the bladder to refill. This dynamic pressure modulation maintains fluid delivery efficiency while preventing excessive deformation that would occur with constant high compression. The mechanism adapts its force application to match the physiological requirements of each phase of the cardiac cycle.
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 apparatus simulates the Windkessel effect, providing adjustable compliance and reducing air infusion, thus maintaining physiologic metabolic conditions and perfusion of the heart under various loading states.
Implementation Method 1
a reactive squeezing mechanism configured to receive the flexible fluid container and to apply compressive pressure to its exterior in response to an increase in fluid within the flexible fluid container
Implementation Method 2
The reactive squeezing mechanism may comprise a back surface, a front plate, and a set of elastic members configured to compress the front plate and back surface together, such that the elastic members provide the compressive pressure
Implementation Method 3
The Windkessel effect is the effect on arterial blood pressure due to the elastic compliance of arteries. Arteries fill with blood and distend during systole, and then recoil during diastole, effectively acting as a hydraulic capacitor
Implementation Method 4
The flexible fluid container may comprise an air elimination port oriented upwards such that it enables air to escape the flexible fluid container
Implementation Method 5
The back surface may be heated
Implementation Method 6
the pump is a pulsatile pump synchronized to the heart in a counter-pulse fashion
Implementation Method 7
a preload reservoir having a positive head height above the heart, and have the heart in a loaded state, where fluid flows from the oxygenator to the preload reservoir, and then to the left atrium of the heart
Data Source
AI summary
A Windkessel simulation apparatus includes a flexible fluid container that cyclically fills with a perfusate fluid, such as blood, and helps deliver the perfusate fluid to a heart, by means of an elastic reactive squeezing mechanism that applies compressive force proportional to the pressure in the flexible fluid container. The apparatus acts as a hydraulic capacitor, similarly to how arteries act in the body-inflating during systole, and squeezing during diastole. In this way, the apparatus may help simulate a natural circulatory system for an organ, such as an ex vivo heart.