Implantable Tissue Perfusion Sensing Using Multi-Wavelength Optical Compensation
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Solution Overview
Problem
Current implantable cardiac devices face challenges in effectively monitoring cardiovascular status without invasive procedures, as non-invasive sensors are prone to interference from spurious electrical signals caused by muscle movement and other factors.
Innovation Solution
A tissue perfusion sensing system using at least two light sources with different wavelengths to measure changes in tissue oxygenation and blood volume, compensating for noise sources like mechanical noise and tissue encapsulation, allowing for reliable detection of cardiac events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-invasive sensors are used to monitor cardiovascular status, then patient comfort and ease of operation are improved, but measurement precision deteriorates due to interference from spurious electrical signals caused by muscle movement
Solution Approach 1:
The patent introduces tissue perfusion sensing as an intermediary measurement method. Instead of directly measuring electrical cardiac signals that are prone to noise interference, the system measures optical properties of tissue (blood volume, oxygenation) that correlate with cardiac events. This intermediary approach allows non-invasive monitoring while avoiding the spurious electrical signals from muscle movement.
Solution Approach 2:
The patent replaces electrical sensing mechanisms with optical sensing mechanisms. By using light sources and photodetectors to measure tissue perfusion characteristics rather than electrical electrodes to detect cardiac potentials, the system eliminates susceptibility to electrical noise from muscle movement while maintaining the ability to detect cardiac events through optical changes in tissue.
2Measurement precision
If multiple light sources with different wavelengths are used to measure tissue perfusion, then measurement precision is improved by compensating for noise sources, but device complexity increases
Solution Approach 1:
The patent segments the measurement process into multiple wavelength channels, each targeting specific tissue characteristics. By dividing the optical spectrum into distinct wavelength bands (e.g., red, infrared) and assigning each to measure specific parameters (blood volume, oxygenation), the system achieves comprehensive tissue perfusion assessment while managing complexity through modular wavelength-specific detection.
Solution Approach 2:
The patent utilizes changes in optical parameters (wavelength, absorption coefficient) to extract multiple tissue characteristics. By measuring light absorption at different wavelengths, the system can distinguish between various tissue components (oxygenated blood, deoxygenated blood, non-hemoglobin chromophores) and compensate for noise sources, achieving high measurement precision without requiring complex hardware for each parameter.
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 system provides accurate monitoring of tissue perfusion, enabling implantable medical devices to determine appropriate actions, such as defibrillation, by distinguishing between perfusion changes and noise artifacts, thus improving cardiac event detection and management.
Implementation Method 1
a first light source provides light at a first wavelength... a second light source provides light at a second wavelength... where light absorption in the tissue is dependent upon the oxygen content of the tissue and the volume of blood in the tissue
Data Source
AI summary
A medical device for sensing cardiac events that includes a plurality of light sources capable of emitting light at a plurality of wavelengths, and a detector to detect the emitted light. A processor determines a plurality of light measurements in response to the emitted light detected by the detector, updates, for each of the plurality of wavelengths, a first normalization coefficient and a second normalization coefficient in response to the detected emitted light, and adjusts the determined plurality of light measurements in response to the first normalization coefficient and the second normalization coefficient.