LVAD Controller Algorithm for Suction Management
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Solution Overview
Problem
Implantable blood pumps can create suction conditions within the ventricle when operated at excessive flow rates, leading to rapid decline in flow rate and inadequate circulatory assistance to the patient.
Innovation Solution
A controller for an implantable blood pump that adjusts the impeller speed based on detected suction events, reducing the speed to a first reduced speed if a predetermined amount of suction is detected within a specific time interval, and increasing the speed if suction events decrease to a predetermined level within a different time interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the VAD is operated at a flow rate in excess of an inflow rate of blood to the ventricle, then the pump provides sufficient circulatory assistance, but the VAD creates a suction condition within the ventricle causing the ventricle to collapse and flow rate to decline rapidly
Solution Approach 1:
The controller continuously monitors suction events and adjusts impeller speed based on detected suction conditions. When suction is detected, the controller reduces impeller speed to prevent ventricle collapse, and when suction is resolved, the controller increases speed to maintain adequate circulatory assistance. This closed-loop feedback control resolves the contradiction by dynamically adjusting flow rate based on real-time ventricle conditions.
Solution Approach 2:
The system transitions from a static fixed-speed operation to a dynamic variable-speed operation. The impeller speed is continuously adjusted based on detected suction events, allowing the pump to adapt its flow rate to match the varying inflow rate from the ventricle. This dynamic adjustment prevents both ventricle collapse and inadequate circulatory assistance.
2Reliability
If the flow rate through the pump is reduced to prevent suction, then the ventricle collapse is avoided, but the device will not provide sufficient circulatory assistance to the patient
Solution Approach 1:
The controller implements periodic monitoring of suction events at different time scales (short-term 1-second intervals and long-term 10-second intervals). This periodic detection allows the system to distinguish between transient and sustained suction conditions, adjusting impeller speed accordingly to maintain both ventricle function and adequate circulatory assistance.
Solution Approach 2:
The controller reduces impeller speed in advance when suction is detected, preventing ventricle collapse before it occurs. By proactively reducing speed rather than reacting after collapse, the system maintains both ventricle integrity and adequate flow to the patient.
3Reliability
If the controller reduces impeller speed to resolve suction, then ventricle collapse is prevented, but the response time and complexity of the control system increases
Solution Approach 1:
The control algorithm is segmented into distinct time intervals (1-second short-term interval and 10-second long-term interval) with different response thresholds. This segmentation simplifies the control logic by creating clear decision boundaries based on suction duration, making the algorithm more manageable while maintaining reliable suction resolution.
Solution Approach 2:
The controller changes the monitoring parameters (time intervals and suction thresholds) to optimize the balance between response accuracy and algorithm complexity. By using predetermined thresholds and fixed time intervals, the system achieves reliable suction detection without requiring complex real-time analysis.
Data Source
AI summary
A controller for an implantable blood pump, the implantable blood pump having an impeller. The controller includes processing circuitry configured to reduce a speed of the impeller from a set speed to a first reduced speed if a first predetermined amount of time of detected suction events occurs during a first time interval and increase the speed of the impeller from the first reduced speed if a second predetermined amount of time or less of detected suction events occur during a second time interval and a third predetermined amount of time or less of detected suction events.