PPG Cardiac Stability Analysis via Amplitude and Pulse Period Variance
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Solution Overview
Problem
Current methods for determining cardiac stability often require invasive ECG systems and are not efficient in providing quick, inexpensive, and sensitive measurements of cardiac output and stroke volume.
Innovation Solution
A photoplethysmography (PPG) system that includes a sensor and monitor configured to analyze amplitude variance and pulse period variance of PPG signals to calculate cardiac stability ratio, allowing for non-invasive determination of cardiac stability without the need for ECG systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive ECG systems are used to determine cardiac stability, then measurement precision is improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The patent replaces the mechanical/electrical ECG system with an optical PPG system. The PPG sensor uses light absorption changes to detect blood volume variations, substituting the electrical field-based ECG method with an optical field-based method, thereby reducing system complexity while maintaining measurement capability
Solution Approach 2:
The patent uses PPG signal characteristics (amplitude and temporal variations) as a copy or proxy for direct cardiac output measurement. By analyzing the photoplethysmogram waveform properties, the system indirectly determines cardiac stability without requiring direct invasive measurement of cardiac parameters
2Measurement precision
If traditional SV calculation using echocardiogram is used, then measurement precision is improved, but use of energy and device complexity worsen
Solution Approach 1:
The patent substitutes the mechanical ultrasound-based echocardiogram system with an optical PPG system. The PPG sensor consumes significantly less power than ultrasound imaging equipment while providing sufficient measurement precision for cardiac stability assessment through optical detection of blood volume changes
3Ease of operation
If PPG system is used to determine cardiac stability, then ease of operation and use of energy are improved, but measurement precision may deteriorate
Solution Approach 1:
The patent employs feedback mechanisms by continuously monitoring PPG signal characteristics (amplitude variance and temporal variance) and using these measurements to calculate cardiac stability metrics. The system processes the PPG waveform data through algorithms that provide real-time feedback on cardiac stability, maintaining measurement precision through continuous adaptive monitoring
Solution Approach 2:
The patent analyzes changes in PPG signal parameters (amplitude and temporal characteristics) to determine cardiac stability. By monitoring how these parameters vary over time, the system extracts meaningful cardiac stability information from the PPG signal, maintaining measurement precision through parameter analysis rather than direct measurement
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
Enables quick, frequent, and sensitive determination of cardiac stability with minimal power consumption, providing a reliable indicator of cardiac health and potential conditions like hypovolemia.
Implementation Method 1
The PPG system performs a non-invasive, optical measurement that may be used to detect changes in blood volume within tissue, such as skin, of an individual
Data Source
AI summary
A PPG system includes a processor configured to receive a PPG signal from a PPG sensor, the PPG signal having a plurality of pulses each representing a heartbeat of a patient. The processor is also configured to determine an amplitude variance of the plurality of pulses over a time period, determine a pulse period variance of the PPG signal over the time period, determine a cardiac stability based on a ratio of the amplitude variance and the pulse period variance, and provide an indication of the cardiac stability via a display. The amplitude variance includes an average of squared differences of an amplitude of a peak of each pulse of the plurality of pulses from a mean amplitude of the plurality of pulses over the time period, and the mean amplitude includes an average of respective midpoints of each of the plurality of pulses over the time period.