Optical Sensor Tissue Oxygen Saturation Shock Reduction
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Solution Overview
Problem
Current implantable cardioverter defibrillators (ICDs) face challenges in distinguishing between hemodynamically stable and unstable arrhythmias, leading to unnecessary shock therapies and battery drain, due to the lack of precise oxygen saturation and hemoglobin volume fraction measurements.
Innovation Solution
An optical sensor system that uses multiple wavelengths to measure absolute tissue oxygen saturation and total hemoglobin volume fraction, providing calibrated data to differentiate between stable and unstable arrhythmias, thereby optimizing the delivery of shock therapies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an uncalibrated oxygen saturation index is used to detect arrhythmias, then the device can monitor patient hemodynamics, but the broad statistical distribution of responses reduces specificity in differentiating between hemodynamically stable and unstable arrhythmias
Solution Approach 1:
The patent transforms the uncalibrated oxygen saturation index into an absolute calibrated measurement by introducing calibration constants and accounting for optical path length variations. This parameter change enables precise differentiation between stable and unstable arrhythmias by providing absolute tissue oxygen saturation values rather than relative indices.
Solution Approach 2:
The patent introduces total hemoglobin concentration as an intermediary parameter to correct the oxygen saturation measurements. By measuring both the oxygen saturation index and total hemoglobin, the system can differentiate between changes due to oxygenation versus changes due to blood volume, thereby improving arrhythmia detection specificity.
2Reliability
If shock therapy is delivered for all detected arrhythmias, then life-threatening conditions are treated, but unnecessary shocks are delivered for hemodynamically stable arrhythmias causing patient discomfort and battery drain
Solution Approach 1:
The patent implements a feedback mechanism where absolute tissue oxygen saturation measurements continuously inform the decision-making process for shock delivery. The system monitors oxygen saturation trends and only triggers shock therapy when the measurements indicate hemodynamic instability, thereby avoiding unnecessary shocks for stable arrhythmias while maintaining reliable treatment for life-threatening conditions.
3Measurement precision
If multiple wavelengths are used to measure oxygen saturation and hemoglobin, then absolute calibrated tissue oxygenation data is obtained, but the device complexity increases
Solution Approach 1:
The patent designs the optical sensor system to perform multiple functions using the same hardware components. The same light sources and photodetectors used for measuring oxygen saturation are also utilized for measuring total hemoglobin concentration and determining optical path length. This multi-functionality approach achieves precise tissue oxygenation measurements without proportionally increasing device complexity.
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 effectively reduces unnecessary shock therapies by accurately distinguishing between hemodynamically stable and unstable arrhythmias, conserving battery life and improving patient comfort.
Implementation Method 1
an optical sensor detecting two or three light wavelengths for monitoring patient hemodynamics
Data Source
AI summary
An implantable medical device for detecting and treating an arrhythmia includes an optical sensor adapted for positioning adjacent to a blood-perfused tissue volume. In one embodiment for controlling arrhythmia therapies delivered by the device, the optical sensor is controlled to emit light in response to detecting an arrhythmia, detect light scattered by the volume of blood perfused tissue including measuring an optical sensor output signal corresponding to the intensity of scattered light for at least four spaced-apart wavelengths, and compute a volume-independent measure of tissue oxygen saturation from the detected light. The hemodynamic status of the arrhythmia is detected in response to the measure of tissue oxygen saturation.