Respiration Measurement at Extremities Using AC-Modulation Isolation
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Solution Overview
Problem
Existing systems for measuring respiration rate at extremities, such as the wrist, face significant noise issues due to electromagnetic interference (EMI), leading to errors in determining the correct respiration rate.
Innovation Solution
The implementation of separate user-excitation contacts for AC modulation signals, addition of low-pass filters, capacitance between impedance-measuring contacts, and digital filtering to remove noise and DC components, allowing for accurate impedance measurement and respiration rate determination at extremities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurement is performed at extremities using AC modulation signals, then respiration rate can be determined, but electromagnetic interference causes significant noise and measurement errors
Solution Approach 1:
The patent divides the measurement system into separate functional components: excitation signal generation, impedance measurement, and signal processing. By segmenting the contacts into excitation contacts and measurement contacts, the system isolates the AC modulation signals from the impedance measurement path, reducing EMI impact on the respiration rate determination
Solution Approach 2:
The patent introduces low-pass filters as intermediary components between the impedance measurement contacts and the signal processing unit. These filters act as mediators that block high-frequency EMI noise while allowing the lower-frequency respiration signals to pass through, significantly reducing noise in the measurement
2Measurement precision
If low-pass filters and capacitance are added to reduce noise, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent extracts and removes the DC component from the impedance measurement signal through dedicated DC removal circuitry. By separating the DC offset removal function from the overall measurement system, the patent simplifies the filtering requirements for AC respiration signals while maintaining measurement accuracy
Solution Approach 2:
The patent employs automatic gain control and adaptive filtering algorithms that self-adjust based on the measured signal characteristics. These self-service features reduce the need for manual calibration and complex fixed-parameter circuit design, achieving high measurement accuracy with adaptable rather than overly complex hardware
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
Significantly reduces noise and improves the accuracy of respiration rate measurement at extremities by isolating modulation signals and using filtering techniques, resulting in a more reliable and precise determination of inhalation and exhalation phases.
Implementation Method 1
Some existing systems and methods for measuring a user's respiration rate rely on a change in the impedance of the user's chest. That change in impedance is caused by two aspects of a user's respiration: a change in the volume of gas in relation to the surrounding tissue; and a change in the electrical path length across the chest that is caused by the expansion of the chest.
Implementation Method 2
addition of low-pass filters, capacitance between impedance-measuring contacts, and digital filtering to remove noise and DC components
Data Source
AI summary
Systems and methods measure impedance across a user's chest during respiration to determine a rate of respiration. With AC-modulation contacts separated from impedance-measuring contacts, analog filtering to remove EMI, a bridging capacitor to remove DC noise, and digital filtering to further remove EMI, a user's respiration may be measured with the AC-modulation contacts and the impedance-measuring contacts placed at user extremities.