Pulse Oximetry Waveform Correction for Intravascular Volume
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Solution Overview
Problem
Accurate estimation of intravascular blood volume and fluid responsiveness is challenging, especially in critically ill patients, due to the invasive nature of existing methods and the influence of respiratory and other patient parameters on pulse oximetry waveform measurements.
Innovation Solution
A system that adjusts pulse oximetry waveform measurements to account for variations in respiratory and other patient parameters using a ventilator-controlled respiratory system, incorporating sensors for respiratory and patient parameters to provide a more accurate estimate of intravascular volume and fluid responsiveness, enabling non-invasive monitoring and potential for closed-loop fluid therapy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive arterial line is inserted to obtain accurate pulse pressure waveform, then measurement precision of intravascular volume is improved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The patent replaces the mechanical invasive arterial line system with an optical pulse oximetry system. The pulse oximeter uses light absorption measurements through a non-invasive sensor to obtain plethysmographic waveforms, eliminating the need for arterial puncture and line insertion while providing sufficient data for intravascular volume assessment when combined with respiratory parameter corrections
Solution Approach 2:
The patent introduces respiratory parameters (tidal volume, respiratory rate, positive end-expiratory pressure) as intermediary variables that mediate between the non-invasive pulse oximetry measurement and the intravascular volume assessment. By measuring and correcting for respiratory influences on the plethysmographic waveform, the system bridges the gap between simple optical measurement and accurate volume estimation
2Ease of operation
If pulse oximetry waveform measurements are used to estimate intravascular volume, then ease of operation is improved, but measurement precision deteriorates due to respiratory parameter influences
Solution Approach 1:
The patent implements a feedback mechanism where respiratory parameters are continuously measured and used to adjust the interpretation of pulse oximetry waveforms. The system monitors tidal volume, respiratory rate, and PEEP levels, then uses these measurements to correct the plethysmographic waveform analysis, ensuring that respiratory variations do not falsely indicate intravascular volume changes
Solution Approach 2:
The patent changes the analysis parameters of the pulse oximetry waveform by incorporating respiratory phase information. Instead of analyzing the waveform in isolation, the system adjusts its analysis based on the respiratory cycle phase, tidal volume magnitude, and PEEP level, transforming the raw optical signal into an accurate volume assessment that accounts for respiratory mechanics
3Measurement precision
If respiratory parameters are measured and used to adjust pulse oximetry measurements, then measurement precision of intravascular volume is improved, but device complexity increases
Solution Approach 1:
The patent makes the pulse oximeter multi-functional by enabling it to perform both its traditional oxygen saturation monitoring function and intravascular volume assessment. The same optical sensor and processor that measure SpO2 also analyze the plethysmographic waveform and, when combined with respiratory parameters from the ventilator, provide volume estimation without requiring separate dedicated sensors or devices
Solution Approach 2:
The patent merges the pulse oximetry system with the ventilator monitoring system. By integrating the respiratory parameter data from the ventilator with the pulse oximetry waveform analysis, the system creates a unified monitoring platform that simultaneously tracks respiratory mechanics and intravascular volume status, reducing overall system complexity compared to using separate independent systems
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 allows for more accurate and rapid assessment of intravascular volume, enabling informed decisions on fluid therapy and earlier intervention, with the potential for improved patient outcomes by correcting plethysmographic waveform variability for respiratory influences and other clinical conditions.
Implementation Method 1
optical pulse oximetry sensor that transmits two or more wavelengths of light, most commonly red and near infrared wavelengths, through a patient's tissue and that photoelectrically detects the absorption and/or scattering of the transmitted light in such tissue
Implementation Method 2
photoelectrically detects the absorption and/or scattering of the transmitted light in such tissue
Data Source
AI summary
Embodiments of the present invention relate to a system and method for determining a physiologic parameter of a patient. Specifically, embodiments of the present invention include methods and systems for correcting a pulse oximetry plethysmographic waveform variability measurement based on parameters that may influence the waveform variability. The corrected measurement may be used to estimate intravascular blood volume and/or fluid responsiveness of a patient.