LVAD Cannula Thermal Anemometry for Accurate Pump Flow Sensing
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Solution Overview
Problem
Existing methods for determining heart-time volume (QHTV) in implanted left-heart support systems (LVAD) are inaccurate and limited to surgical scenarios, relying on dilution methods or statistical assumptions, which are error-prone and difficult to implement outside cardiac surgery.
Innovation Solution
A method utilizing thermally anemometric principles with integrated heating elements and temperature sensors in the cannula of the support system to measure fluid volume flow (Qp) by determining fluid temperature parameters and operating heating elements to calculate Qp, employing constant current, constant temperature, or pulse response methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dilution methods are used to determine heart-time volume, then measurement can be performed during cardiac surgery, but the method is limited to surgical scenarios and requires catheter insertion
Solution Approach 1:
The patent replaces the mechanical catheter-based dilution method with a thermal anemometry system that uses heating elements and temperature sensors integrated into the LVAD cannula. This substitution enables continuous measurement outside surgical scenarios without requiring catheter insertion, resolving the contradiction between measurement precision and adaptability.
Solution Approach 2:
The LVAD system performs self-measurement of pump volume flow using integrated thermal sensors and heating elements. The system uses its own operational parameters (power consumption, temperature differential) to determine flow, eliminating the need for external catheter-based measurement systems and enabling continuous monitoring during daily use.
2Device complexity
If statistical assumptions and pump characteristic maps are used to determine pump volume flow, then measurement can be performed without flow sensors, but the correlated Qp values are error-prone
Solution Approach 1:
The patent replaces statistical correlation methods with direct thermal measurement. By using heating elements and temperature sensors to directly measure the thermal field in the blood flow, the system obtains accurate pump volume flow values without relying on statistical assumptions or pump characteristic maps, thereby improving measurement precision while maintaining reasonable system complexity.
Solution Approach 2:
The patent introduces temperature as an intermediary parameter to measure pump volume flow. Instead of directly measuring flow or using statistical correlations, the system uses temperature differential and thermal field characteristics as an intermediary to indirectly and accurately determine pump volume flow, resolving the contradiction between device complexity and measurement precision.
3Measurement precision
If flow sensors are included to increase measurement quality of pump volume flow, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the heating element serve dual functions: as a thermal stimulus for measurement and as part of the thermal field being measured. The same heating element that warms the blood also serves as a reference for temperature differential measurement, reducing the need for separate sensors and minimizing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent combines the heating element and temperature sensing functionality into an integrated thermal measurement system. By merging the thermal stimulus and measurement functions within the cannula structure, the system achieves accurate pump volume flow measurement without requiring separate flow sensors, thereby improving measurement quality while controlling device complexity.
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
Enables continuous and precise measurement of Qp outside surgical scenarios with comparable quality to dilution catheters, preventing tissue damage and simplifying calibration, and allowing rapid diagnosis of suction issues.
Implementation Method 1
operating a heating element which can bring about a change in a fluid temperature in the cannula
Implementation Method 2
determining a fluid temperature parameter in the region of a cannula of the support system
Data Source
AI summary
The invention relates to a method for determining a fluid volume flow (1) through an implanted vascular support system (2), comprising the following steps: a) determining a fluid temperature parameter in the region of a cannula (4) of the support system (2), b) operating a heating element (5) which can bring about a change in a fluid temperature in the cannula (4), c) determining the fluid volume flow (1) using at least the fluid temperature parameter or the change thereof and at least one heating element operating parameter or the change thereof. The invention also relates to a vascular support system.