Ventricular Assist Device Impeller Flow Estimation
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Solution Overview
Problem
Existing ventricular assist devices (VADs) face challenges in accurately measuring blood flow rate due to the complexity and reliability issues associated with direct measurement methods, such as flow sensors, which can lead to imprecise estimations over time and potential thrombosis risks.
Innovation Solution
A blood pump system that estimates flow rate by measuring the thrust load applied to a rotating impeller using sensors that generate output indicative of the reaction force or displacement, allowing for more accurate flow rate estimation based on impeller rotational speed and thrust load, rather than relying solely on power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement components (flow sensor) are added to measure blood flow rate, then measurement precision is improved, but device complexity increases and reliability decreases
Solution Approach 1:
The patent extracts the flow measurement function from direct sensor-based measurement and relocates it to an indirect measurement approach using existing components (power sensor, rotational speed sensor) that are already present in the VAD system, thereby avoiding addition of complex flow sensor components while maintaining measurement capability
Solution Approach 2:
The patent introduces an intermediary calculation model that relates power consumption and rotational speed to flow rate through mathematical modeling, serving as a mediator between the easily measurable parameters (power, speed) and the desired flow rate parameter, eliminating the need for direct flow sensing
2Measurement precision
If flow sensor is placed in the flowpath to measure blood flow rate, then measurement precision is improved, but harmful factors increase due to thrombosis risk
Solution Approach 1:
The patent removes the flow sensor from the blood flow path entirely, extracting the measurement function from the fluid environment and implementing it through indirect electrical and mechanical parameter measurement, thereby eliminating the thrombosis hazard associated with sensor placement in the flowpath
Solution Approach 2:
The patent replaces the mechanical/sensor-based direct flow measurement system with an electrical and computational approach, substituting physical measurement components with electrical parameter sensing and mathematical modeling to eliminate contact between measurement devices and blood
3Measurement precision
If existing flow sensors are used to measure blood flow rate, then measurement capability is provided, but measurement precision deteriorates over time due to drift
Solution Approach 1:
The patent implements feedback through continuous monitoring of power consumption and rotational speed parameters, using these feedback signals in real-time calculations to determine flow rate, thereby maintaining measurement accuracy over time without suffering from sensor drift
Solution Approach 2:
The patent changes the measurement parameters from direct flow sensing to electrical and mechanical parameter sensing (power, speed), which are more stable over time and do not exhibit drift, thereby improving long-term measurement precision and stability
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
This method provides a more accurate estimation of blood flow rate and pressure drop across the pump, enhancing clinical monitoring and optimizing pump operation, while minimizing the risk of thrombosis and complexity.
Implementation Method 1
The motor stator is mounted to the housing and operable to magnetically rotate the impeller
Implementation Method 2
The sensor generates a sensor output indicative of a magnitude of the thrust load reacted by the support member
Data Source
AI summary
A circulation assist system measures impeller displacement for use in estimating a blood flow rate related parameter. A circulation assist system includes a blood pump and a controller. The blood pump includes an impeller magnetically supported within a blood flow channel. The blood pump includes one or more sensors configured to generate output indicative of displacement of the impeller along the blood flow channel induced by a blood-flow induced thrust load applied to the impeller. The controller is configured to process the output generated by the one or more sensors to determine the displacement of the impeller along the blood flow channel. The controller is configured to process the determined displacement of the impeller to estimate at least one of the thrust load applied to the impeller, a pressure differential of the blood impelled through the blood flow channel, and a flow rate of blood pumped by the blood pump.