Noninvasive CVP Measurement via Forehead PPG and Adaptive Filtering
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Solution Overview
Problem
Current methods for measuring central venous pressure (CVP) are invasive, prone to complications, and not suitable for routine monitoring, especially since they often require central venous catheter insertion, which can lead to infections and other issues.
Innovation Solution
A sensor system integrating photoplethysmography (PPG) with pressure transducers and accelerometers to non-invasively measure CVP and respiratory effort, capable of being integrated into devices like APAP, CPAP, and VPAP, using adaptive filtering and signal processing to extract venous pressure changes from surface measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If central venous catheter insertion is used to measure CVP, then measurement precision is improved, but object-affected harmful factors worsen due to infections and complications
Solution Approach 1:
The patent replaces the mechanical/invasive catheter-based measurement system with an optical measurement system using photoplethysmography. The PPG sensor detects venous pressure changes through light absorption changes in the forehead veins, eliminating the need for catheter insertion while maintaining measurement capability through non-invasive optical detection
Solution Approach 2:
The patent uses the forehead veins as an intermediary medium to indirectly measure central venous pressure. By detecting venous pressure changes in the accessible forehead veins and correlating them with CVP through signal processing, the system avoids direct catheter insertion into central veins while still obtaining accurate CVP measurements
2Measurement precision
If central venous catheter insertion is used to measure CVP, then measurement precision is improved, but device complexity worsens due to invasive procedure requirements
Solution Approach 1:
The patent replaces the complex invasive catheter insertion procedure with a simple optical sensor placement on the forehead. The measurement system uses light emission and detection through the skin and veins, eliminating all procedural complexity associated with sterile catheter insertion, vein selection, and catheter maintenance
Solution Approach 2:
The patent utilizes the body's own venous system as the measurement medium. The forehead veins naturally provide access to venous pressure information, and the system leverages this existing physiological structure without requiring external invasive intervention, simplifying the overall measurement approach
3Object-affected harmful factors
If photoplethysmography with pressure transducers is used, then object-affected harmful factors are reduced by eliminating invasive procedures, but measurement precision may worsen due to signal extraction challenges
Solution Approach 1:
The patent employs adaptive filtering that continuously adjusts based on the detected signal characteristics. The system analyzes the PPG signal in real-time, identifies venous pressure-related components, and adjusts filtering parameters to optimize extraction accuracy, ensuring precise CVP measurement from the non-invasive optical signal
Solution Approach 2:
The patent extracts the specific venous pressure signal component from the complex PPG signal through adaptive filtering and signal processing. By isolating the relevant physiological information from noise and other signal components, the system achieves accurate CVP measurement despite the non-invasive measurement approach
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 accurate, non-invasive monitoring of CVP and respiratory effort, reducing complications associated with invasive methods and providing real-time data for improved patient management and treatment efficacy.
Implementation Method 1
A sensor system integrating photoplethysmography (PPG) with pressure transducers and accelerometers to non-invasively measure CVP and respiratory effort
Data Source
AI summary
Photoplethysmography (PPG) is obtained using one red (e.g., 660 nm) and one infrared (e.g., 880 to 940 nm) light emitting diode with a single photo diode in combination with a pressure transducer thereby allowing both CVP and SpO2 to be measured simultaneously. The system also includes sensors capable of measuring position, angle and/or movement of the sensor or patient. Once the PPG signal is acquired, high pass adaptive and/or notch filtering can be used with one element of the filter from the red and infrared signals used to measure the arterial changes needed to compute SpO2 and the other element of the signal can be used to measure CVP changes.