Bioelectrical Impedance Measurement Using Preliminary Averaging
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Solution Overview
Problem
Existing cardiac output monitor systems require high power consumption due to the need for a large number of effective bits in analog-digital converters to accurately calculate cardiac output and pulmonary artery wedge pressure, which shortens the implantable medical instrument's operational time.
Innovation Solution
A bioelectrical impedance measuring apparatus that includes an impedance measuring unit, an amplification unit, and a control unit to modulate and demodulate currents, amplify voltages, and adjust inspection currents and correction voltages to keep the AD converter output within its dynamic range, allowing for precise impedance averaging and variation detection with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of effective bits are used in the AD converter to accurately detect impedance variations, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by performing impedance averaging before AD conversion. The impedance averaging unit calculates the average impedance value from multiple measurements prior to conversion, thereby reducing the dynamic range requirements and enabling the use of lower-resolution AD converters with fewer effective bits, which directly reduces power consumption while maintaining measurement accuracy
Solution Approach 2:
The patent introduces an intermediary component - the impedance averaging unit - that processes raw impedance signals before they reach the AD converter. This intermediary performs signal conditioning and averaging, transforming the input signal into a form that requires fewer bits for accurate representation, thus bridging the gap between high-precision measurement requirements and low-power conversion capabilities
2Measurement precision
If a large number of effective bits are used in the AD converter to accurately detect impedance variations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
By performing impedance averaging before AD conversion, the system reduces the complexity requirements of the AD converter. The preprocessing of impedance data eliminates the need for high-resolution conversion, allowing the use of simpler, lower-bit AD converters that are less complex in terms of circuit design, manufacturing, and integration
Solution Approach 2:
The impedance averaging unit serves as an intermediary that simplifies the overall system architecture. By handling the complex signal processing tasks before conversion, it allows the AD converter to be a simpler component, reducing the overall device complexity while maintaining the capability for precise impedance detection
3Duration of action of moving object
If power consumption is reduced by using fewer effective bits in the AD converter, then operational time is extended, but measurement precision deteriorates
Solution Approach 1:
The patent performs impedance averaging as a preliminary processing step before AD conversion. This preprocessing concentrates the signal energy and reduces noise, allowing lower-resolution converters to maintain adequate measurement precision. The averaging process ensures that even with fewer effective bits, the operational time is extended while measurement precision remains sufficient for clinical use
Solution Approach 2:
The patent changes the parameter of impedance representation by converting raw impedance values into averaged impedance values. This parameter transformation reduces the dynamic range and variability of the signal, enabling the use of lower-resolution AD converters that consume less power while still providing accurate enough measurements for cardiac output and pulmonary artery wedge pressure calculations
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
The apparatus achieves precise detection of bioelectrical impedance averages and variations while minimizing power consumption, even with AD converters having a small number of effective bits, thereby extending the operational time of implantable medical instruments.
Implementation Method 1
an impedance measuring unit for applying an inspection current to a living body and measuring an inspection voltage
Implementation Method 2
an amplification unit for amplifying the inspection voltage and outputting an amplified voltage within an input dynamic range of an AD converter
Implementation Method 3
AD converter having a small number of effective bits
Data Source
AI summary
A bioelectrical impedance measuring apparatus may include an impedance measuring unit configured to provide an inspection current based on a predetermined current to a living body, and obtain an inspection voltage corresponding to an impedance of the living body, an amplification unit configured to amplify the inspection voltage with reference to a correction voltage, an AD converter configured to AD-convert an output of the amplification unit, and a control unit configured to control the inspection current and the correction voltage based on an AD-converted result of the AD converter such that the output of the amplification unit is within an input dynamic range of the AD converter, and calculate an impedance average of the living body and an impedance variation of the living body based on the predetermined current, the correction voltage and the AD-converted result.