Cardiac-Impedance Signal Calibration for Low-Power Fluid Status Detection
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Solution Overview
Problem
Existing implantable medical devices face a high power burden when performing frequent impedance measurements for fluid status monitoring, which depletes the limited power supply quickly, reducing the device's functional life.
Innovation Solution
Combining cardiac electrical signals with impedance measurements to reduce power consumption, using cardiac electrical signal amplitudes in conjunction with impedance measurements to generate a fluid status signal, allowing for more frequent and efficient monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurements are performed frequently for fluid status monitoring, then monitoring precision is improved, but power consumption increases
Solution Approach 1:
The patent combines impedance measurements with cardiac electrical signal analysis to create a unified fluid status monitoring system. By merging these two measurement approaches, the system achieves comprehensive fluid status monitoring while reducing overall power consumption compared to using impedance measurements alone.
Solution Approach 2:
The system implements periodic impedance measurements calibrated by cardiac electrical signals. Instead of continuous impedance monitoring, the device uses periodic impedance measurements that are referenced against cardiac electrical signal amplitudes, reducing power consumption while maintaining monitoring precision.
2Reliability
If impedance measurements are performed frequently for fluid status monitoring, then reliability is improved, but device operational life decreases
Solution Approach 1:
The patent merges impedance measurement functionality with cardiac electrical signal processing to create a dual-purpose system. This combination allows the device to maintain reliable fluid status monitoring through periodic impedance measurements while using cardiac signals for continuous monitoring, thereby extending device operational life.
Solution Approach 2:
The system uses the patient's own cardiac electrical signals as a reference for calibrating impedance measurements. This self-service approach eliminates the need for external calibration equipment and reduces the frequency of full impedance measurements, thereby extending device operational life while maintaining reliability.
3Measurement precision
If drive current signals are used for impedance measurements, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The system employs periodic drive current signals for impedance measurements rather than continuous signals. The drive current is applied in periodic bursts synchronized with cardiac cycles, allowing precise impedance measurement while minimizing overall power consumption.
Solution Approach 2:
The system changes the amplitude and duration parameters of drive current signals based on cardiac electrical signal detection. By adjusting drive current parameters dynamically according to cardiac activity, the system maintains measurement precision while optimizing power consumption.
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 enables frequent and power-efficient monitoring of fluid status by reducing the reliance on external drive current signals, extending the device's operational life and improving monitoring frequency.
Implementation Method 1
Impedance of body tissues exposed to an applied electrical current (or voltage signal) produces a voltage potential (or induced current) across an electrode vector.
Implementation Method 2
The known current and recorded voltage is related to the tissue impedance according to Ohm's Law.
Data Source
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AI summary
A medical device is configured to generate fluid status signal data of a patient by determining impedance metrics from an impedance signal, determining cardiac electrical signal amplitudes from a cardiac electrical signal and determining a calibration relationship between the impedance metrics and cardiac electrical signal amplitudes. The medical device generates a fluid status signal data by adjusting cardiac electrical signal amplitudes according to the determined calibration relationship. The fluid status signal data may be displayed or monitored for detecting a change in the patient's fluid status.