LVAD Cannula Thermal Flow Sensing for Continuous Cardiac Output
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Solution Overview
Problem
Existing methods for measuring cardiac output in implantable left ventricular assist devices (LVADs) are inaccurate and limited to surgical settings, relying on dilution techniques or statistical assumptions, and there is a need for a more precise and continuous method to determine blood volume flow rates.
Innovation Solution
An implantable vascular support system incorporating a heating element and temperature sensors in the cannula to measure fluid volume flow rates using thermal anemometric principles, allowing for continuous and accurate measurement of pump flow rate (Qp) outside the operating room.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If statistical assumptions and pump characteristic curves are used to determine pump flow rate, then measurement can be performed without additional sensors, but measurement precision deteriorates due to errors in correlated Qp values
Solution Approach 1:
The patent replaces statistical and mechanical correlation methods with a thermal measurement system. A heating element integrated into the pump housing heats the blood, and temperature sensors measure the temperature difference to calculate flow rate using thermal principles, providing direct measurement instead of indirect correlation
Solution Approach 2:
The patent introduces thermal energy as an intermediary measurement mechanism. The heating element transfers thermal energy to the blood, and the temperature change serves as a mediator to determine flow rate, creating a new measurement pathway that is more precise than direct mechanical or statistical methods
2Measurement precision
If dilution techniques with transcutaneously inserted catheters are used to measure cardiac output, then measurement precision improves, but ease of operation deteriorates as measurements can only be performed during cardiac surgery
Solution Approach 1:
The patent merges the flow measurement function directly into the LVAD pump housing by integrating a heating element and temperature sensors. This combination eliminates the need for separate catheters and enables continuous measurement during normal device operation, making the system both precise and continuously operable
Solution Approach 2:
The LVAD pump itself performs the measurement function through its integrated heating element and temperature sensors. The pump's operational components are utilized to generate and measure thermal changes in the blood, allowing the device to self-monitor its flow rate without external measurement tools
3Measurement precision
If a heating element is positioned in the center of the blood stream for flow measurement, then measurement precision improves, but object-affected harmful factors worsen due to potential tissue damage
Solution Approach 1:
The patent extracts the heating element from the direct blood flow path and relocates it to the pump housing or cannula wall. This separation removes the harmful thermal source from contact with blood and surrounding tissues while preserving the measurement capability through thermal conduction to the blood
Solution Approach 2:
The pump housing or cannula wall serves as a thermal intermediary between the heating element and the blood. The heating element heats the housing material, which then transfers thermal energy to the blood through conduction, allowing measurement without direct heating element contact with blood or tissues
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 precise and continuous measurement of cardiac output (Qp) comparable to dilution catheters, preventing tissue damage and simplifying calibration, with the system being fully implantable and suitable for both minimally invasive and apical LVAD designs.
Implementation Method 1
b) Operating a heating element (5) that can cause a change in the fluid temperature in the cannula (4)
Implementation Method 2
a) Determining a fluid temperature parameter in the area of a cannula (4) of the support system (2)
Implementation Method 3
An implantable, i.e., arrangable in the human or animal body, vascular support system (2) with a temperature measuring device (3) in the area of a cannula (4) and with a heating element (5) that can cause a change in the fluid temperature in the cannula (4)
Data Source
Figure 1a~1b
Figure 2~3
Figure 4~5
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.