Volume Responsiveness Indicator via Envelope Curve Fitting
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Solution Overview
Problem
Current methods for determining a patient's volume responsiveness, such as systolic pressure variation (SPV) and pulse pressure variation (PPV), are prone to errors due to artefacts and arrhythmias, and require reliable measurement of blood pressure values at each heart beat, which is not feasible with oscillometric non-invasive blood pressure measurement methods.
Innovation Solution
A method involving the measurement of pulse signals, determination of envelope curves, and fitting functions to exclude ventilation-induced heart-lung interactions, followed by calculation of an indicator for volume responsiveness based on these functions, which can be implemented using oscillometric non-invasive blood pressure measurement without requiring constant measurement conditions or single heart beat blood pressure values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methods (SPV, PPV) are used to determine volume responsiveness, then an indicator can be obtained, but the measurement is prone to errors due to artefacts and arrhythmias
Solution Approach 1:
The patent extracts and removes the harmful components (artefacts and arrhythmias) from the pulse signal through signal processing techniques. By separating the respiratory-induced pulse variations from other signal components, the method isolates the clinically relevant information while eliminating sources of error, thereby improving both measurement precision and reliability
Solution Approach 2:
The patent introduces an intermediary processing stage (signal analysis and filtering) between the raw pulse signal measurement and the final volume responsiveness indicator. This intermediary layer processes the signal to remove artefacts and arrhythmias, allowing accurate determination of volume responsiveness even in the presence of these interfering factors
2Measurement precision
If blood pressure values at each heart beat are measured, then accurate volume responsiveness assessment is possible, but this requires invasive methods or constant measurement conditions
Solution Approach 1:
The patent replaces the need for invasive blood pressure measurement or complex constant-condition monitoring with a simpler oscillometric pulse signal measurement. By using signal processing on the oscillometric waveform, the method achieves accurate volume responsiveness assessment without requiring invasive procedures or strict control of measurement conditions
Solution Approach 2:
The patent uses the oscillometric pulse signal as a surrogate or copy that contains sufficient information to determine volume responsiveness without needing direct blood pressure measurements at each heart beat. The envelope curve and its derivatives provide the necessary information from this indirect measurement
Data Source
AI summary
The invention refers to a method of determining an indicator that is representative for a patient's volume responsiveness, comprising the following steps: (i) measuring a sequence of pulse signals of a patient; (ii) determining an envelope(signal)-curve based on the sequence of measured pulse signals; (iii) determining a fit(envelope(signal))-function based on the previously determined envelope(signal)-curve, the fit(envelope(signal))-function representing an idealised curve progression of the envelope(signal)-curve without comprising pulse variations caused by ventilation or respiration induced heart-lung interaction; (iv) determining respiratory pulse variation signals corresponding to the pulse variations caused by ventilation or respiration induced heart-lung interaction; (v) determining an envelope(respiration)-curve based on the previously determined respiratory pulse variation signals; (vi) determining a fit(envelope(respiration))-function based on the previously determined envelope(respiration)-curve, the fit(envelope(respiration))-function representing an idealised curve progression of the envelope(respiration)-curve; (vii) determining the indicator that is representative for the patient's volume responsiveness based on the fit(envelope(signal))-function and the fit(envelope(respiration))-function. The invention also relates to a logic unit and a system, both for determining an indicator representative for the patient's volume responsiveness.