Pulsatile Fluid Delivery Piston Velocity Control
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Solution Overview
Problem
Current cardiopulmonary bypass systems during open-heart surgery struggle to produce a pulsatile flow while maintaining a user-specified average flow rate, which is essential for effective cardiac perfusion.
Innovation Solution
A dual or single chambered pumping apparatus using a piston mechanism to achieve pulsatile flow by cyclically alternating piston velocity, with a microprocessor controlling the flow rate and duty cycle to ensure a desired average flow rate is maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a roller or centrifugal pump is used to deliver fluid, then the average flow rate can be maintained, but the pulsatile flow component is insufficient for effective cardiac perfusion
Solution Approach 1:
The pump system dynamically adjusts the compression ratio of the piston over time, transitioning from a constant compression ratio (producing constant flow) to a variable compression ratio (producing pulsatile flow). The compression ratio is increased during the ejection phase and decreased during the filling phase, creating a pulsatile flow pattern that mimics natural cardiac function while maintaining the desired average flow rate.
Solution Approach 2:
The system implements periodic variation in piston compression ratio to generate pulsatile flow. The compression ratio is periodically increased and decreased in sync with the desired flow pattern, creating rhythmic pulses in fluid delivery that enhance cardiac perfusion while maintaining average flow rate through controlled periodic action.
2Productivity
If the piston compression ratio is increased to produce higher flow rate, then the average flow rate increases, but the pulsatile flow characteristics are reduced
Solution Approach 1:
The system dynamically adjusts the compression ratio of the piston over time, transitioning from a constant compression ratio (producing constant flow) to a variable compression ratio (producing pulsatile flow). The compression ratio is increased during the ejection phase and decreased during the filling phase, creating a pulsatile flow pattern that mimics natural cardiac function while maintaining the desired average flow rate.
Solution Approach 2:
The system changes the compression ratio parameter dynamically during the pump cycle. By varying the compression ratio from one phase to another (higher during ejection, lower during filling), the system achieves both high average flow rate and strong pulsatile characteristics, resolving the trade-off between flow rate and pulsatility.
3Device complexity
If a single chambered pump is used, then the device complexity is reduced, but the ability to produce pulsatile flow with desired characteristics is limited
Solution Approach 1:
The system dynamically adjusts the compression ratio of the piston over time, transitioning from a constant compression ratio (producing constant flow) to a variable compression ratio (producing pulsatile flow). The compression ratio is increased during the ejection phase and decreased during the filling phase, creating a pulsatile flow pattern that mimics natural cardiac function while maintaining the desired average flow rate.
Solution Approach 2:
The system implements periodic variation in piston compression ratio to generate pulsatile flow. The compression ratio is periodically increased and decreased in sync with the desired flow pattern, creating rhythmic pulses in fluid delivery that enhance cardiac perfusion while maintaining average flow rate through controlled periodic action.
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 system effectively delivers blood and cardioplegia solution in a pulsatile flow, simulating natural heart function, thereby enhancing cardiac perfusion and maintaining a consistent average flow rate, which is crucial for myocardial protection during surgery.
Implementation Method 1
a pumping action is achieved by compressing one of the chambers with a piston mechanism
Implementation Method 2
The DeBakey pump uses a pair of rollers to create a peristaltic action against a flexible tube
Data Source
AI summary
A system for delivering blood, cardioplegia solution, and other medications or fluids in a pulsatile flow pattern to a patient during cardiopulmonary bypass is disclosed. In a preferred embodiment, a pumping apparatus having at least one chamber is utilized in which a pumping action is achieved by compressing one of the chambers with a piston mechanism, while allowing the other chamber to fill with fluid via retracting its respective piston. The instantaneous flow rate of either of the chambers is determined by the speed of the piston. In a preferred embodiment, a pulsatile flow of fluid is achieved by cyclically alternating the velocity of the piston between two different speeds. A desired average flow rate and/or delivery pressure and/or constant pulse pressure is maintained by adjusting the alternating velocities at the desired frequency and duty cycle. The calculations necessary to obtain a desired average flow rate are performed by a microprocessor, which also controls the movement of the pistons.