PPG Sensor Stroke Volume Calculation via Slope Transit Time
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Solution Overview
Problem
Current systems for determining stroke volume require multiple sensors and additional monitoring systems, making them complex and less efficient, and are influenced by respiratory effects and pulse transit times.
Innovation Solution
A photoplethysmogram (PPG) system that uses a single sensor to analyze the slope transit time of the PPG signal, calculating stroke volume independently of pulse transit times and respiratory effects, without the need for additional monitoring systems like ECG.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors and additional monitoring systems like ECG are used to determine stroke volume, then measurement precision may be improved, but device complexity increases
Solution Approach 1:
The PPG sensor is designed to perform multiple functions: it measures both pulse rate and stroke volume using a single sensor platform, eliminating the need for separate ECG systems and reducing overall system complexity while maintaining measurement accuracy
Solution Approach 2:
The invention extracts and isolates the specific waveform characteristic (slope transit time of the upslope) that directly correlates with stroke volume, separating this measurement from traditional methods that require multiple sensors and complex signal processing from multiple monitoring systems
2Measurement precision
If traditional PPG systems measure pulse transit times from ECG and PPG signals, then stroke volume can be determined, but the measurement is influenced by respiratory effects and pulse transit times
Solution Approach 1:
The invention extracts only the slope transit time characteristic from the PPG waveform, isolating the measurement from confounding factors such as respiratory effects and pulse transit time variations that affect traditional methods
Solution Approach 2:
The invention changes the measurement parameter from pulse transit time (which is affected by respiratory effects) to slope transit time of the upslope (which directly reflects ventricular ejection characteristics and is independent of respiratory variations)
3Device complexity
If a single PPG sensor is used to determine stroke volume, then device complexity is reduced, but measurement precision may be compromised
Solution Approach 1:
The invention changes the analyzed parameter from traditional pulse transit time to the slope transit time of the upslope, which contains direct information about ventricular ejection and allows accurate stroke volume determination using only a single PPG sensor
Solution Approach 2:
The invention focuses on analyzing only the specific portion of the PPG waveform (the upslope region) that contains the necessary stroke volume information, rather than requiring complete waveform analysis from multiple sensors
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 and simple determination of stroke volume, reducing complexity and improving accuracy by focusing on temporal components of the PPG waveform, thus providing a more reliable measurement.
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 for determining a stroke volume of a patient includes a PPG sensor configured to be secured to an anatomical portion of the patient. The PPG sensor is configured to sense a physiological characteristic of the patient. The PPG system may include a monitor operatively connected to the PPG sensor. The monitor receives a PPG signal from the PPG sensor. The monitor includes a pulse trending module determining a slope transit time of an upslope of a primary peak of the PPG signal. The pulse trending module determines a stroke volume of the patient as a function of the slope transit time.