Regional Oximetry Sensor Ensemble Averaging for Pulse Separation
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Solution Overview
Problem
Regional oximetry sensors face challenges in accurately distinguishing between arterial and venous pulses due to low signal-to-noise ratios, particularly when placed on body locations with weak arterial pulses, such as the forehead, making it difficult to separately determine arterial and venous oxygen saturation.
Innovation Solution
The implementation of ensemble averaging techniques using a trigger signal synchronized with cardiac or respiratory cycles to improve the signal-to-noise ratio by combining similar pulses and assigning weights to them, allowing for the determination of arterial and venous oxygen saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a regional oximetry sensor is placed on body locations with weak arterial pulses (such as the forehead), then the sensor can be positioned on accessible and clinically relevant sites, but the signal-to-noise ratio deteriorates making it difficult to distinguish arterial and venous pulses
Solution Approach 1:
The patent applies periodic action by using ensemble averaging of pulses synchronized to the cardiac cycle. The system identifies periodic arterial pulses caused by heartbeats and venous pulses caused by respiratory cycles, then averages multiple periods of these periodic signals to enhance the signal-to-noise ratio and enable separate determination of arterial and venous oxygen saturation even at sensor locations with weak arterial pulses
Solution Approach 2:
The patent applies preliminary action by first identifying and isolating arterial and venous pulses from the composite PPG signal before performing oxygen saturation calculations. The system uses preliminary signal processing steps including bandpass filtering to separate arterial and venous components, and preliminary identification of pulse waveforms to determine their respective characteristics before final measurement
2Area of stationary object
If the emitter-detector spacing of the regional oximetry sensor is increased to capture more tissue signal, then the measurement coverage is improved, but the ability to separately determine arterial and venous oxygen saturation deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the composite PPG signal into separate arterial and venous components through bandpass filtering and frequency analysis. The system segments the signal based on the different frequency characteristics of arterial pulses (higher frequency from cardiac cycle) and venous pulses (lower frequency from respiratory cycle), allowing separate determination of arterial and venous oxygen saturation despite using a single sensor with extended emitter-detector spacing
3Measurement precision
If ensemble averaging is applied to improve signal-to-noise ratio, then the accuracy of pulse identification is improved, but the processing time and computational complexity increase
Solution Approach 1:
The patent applies partial action by performing ensemble averaging on selected pulse waveforms that meet specific criteria rather than processing all possible signals. The system selectively applies averaging to identified arterial and venous pulses that exhibit characteristic waveform features, reducing unnecessary computational overhead while maintaining measurement accuracy for valid pulses
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 approach enhances the accuracy of oxygen saturation measurements by effectively isolating and averaging arterial and venous pulses, improving the signal quality and enabling precise determination of physiological parameters like regional arterial, venous, and mixed oxygen saturations.
Implementation Method 1
a non-invasive sensor that passes light through a portion of a patient's blood perfused tissue and photo-electrically senses the absorption and scattering of light in such tissue
Data Source
AI summary
A method may include receiving, at a processor, a first electromagnetic radiation signal and a second electromagnetic radiation signal from a regional oximetry sensor having two or more detectors and two or more emitters. The method may also include receiving, at the processor, a trigger signal that has a frequency corresponding to a periodic physical activity of a patient. Additionally, the method may include generating, via the processor, one or more ensemble averaged signals based at least in part on the first and second electromagnetic radiation signals and the trigger signal. Further, the method may include calculating, via the processor, a regional oxygen saturation value based at least in part on the one or more ensemble averaged signals and displaying, via a display, the regional oxygen saturation value.