Concurrent Impedance Plethysmograph Processing
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Solution Overview
Problem
Current impedance plethysmographs have inefficiencies in processing and waveform selection, leading to slow data acquisition and inclusion of distorted waveforms, resulting in reduced accuracy and incomplete use of cardiac cycles.
Innovation Solution
Implementing concurrent processing to store and extract ECG and impedance waveforms simultaneously, allowing for concurrent waveform extraction, selection, averaging, measurement, and display, and using template matching for improved waveform selection based on shape similarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sequential processing is used for waveform extraction, selection, averaging, measurement and display, then device complexity is reduced, but data acquisition speed decreases and only about 1 in 3 or 1 in 4 waveforms can be captured
Solution Approach 1:
The processing system is divided into multiple independent concurrent processes: waveform extraction process, waveform selection process, averaging process, measurement process, and display process. Each process operates independently on different aspects of the data stream, allowing simultaneous execution without interference, thereby achieving full waveform capture while maintaining manageable complexity through modular design
Solution Approach 2:
The patent transitions from sequential single-threaded processing to multi-threaded concurrent processing, adding a temporal dimension to the processing architecture. Multiple processing streams run in parallel across different time slices, effectively transforming the processing capacity from linear to multi-dimensional, enabling all waveforms to be captured and processed simultaneously
2Measurement precision
If simple amplitude-based waveform selection is used, then device complexity is reduced, but measurement precision decreases due to inclusion of distorted waveforms
Solution Approach 1:
A template matching mechanism is implemented where a reference waveform template is established from correctly identified waveforms. Each candidate waveform is compared against this template, and only those matching within a predefined similarity threshold are selected for averaging. This feedback-based selection process continuously refines waveform quality by using previously validated waveforms to guide future selections, significantly improving measurement precision while maintaining reasonable system complexity
Solution Approach 2:
The waveform selection criterion is changed from simple amplitude thresholds to a shape-based similarity parameter. By comparing the temporal pattern and morphology of waveforms against a reference template, the system can distinguish between valid waveforms and distorted ones even when amplitudes are similar, thereby improving selection accuracy without requiring complex hardware modifications
Data Source
AI summary
A system and method for measuring the impedance and impedance changes in a body segment are disclosed. By utilizing an ECG buffer, at least one plethysmograph buffer, and concurrently performing at least extraction of an ECG waveform stored in the ECG buffer and extraction of impedance waveforms stored in the at least one plethysmograph buffer, enhanced signal-to-noise ratios of output signals of impedance plethysmographs are achieved. In an embodiment, improved waveform selection using template matching is also achieved. With template matching, a new candidate waveform is compared in shape to the previous average waveform and may be accepted for current averaging based on the comparison.