Pulse Pressure Variation Calculation Using Baseline Extraction
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Solution Overview
Problem
Existing algorithms for determining pulse pressure variation (PPV) are unreliable due to baseline changes, irregular heartbeats, and varying phases between cardiac and ventilation cycles, leading to falsely elevated or diminished values that can mislead clinicians in assessing fluid responsiveness, potentially causing complications in hypovolemia or hypervolemia.
Innovation Solution
A method that involves extracting the baseline from the pulse height signal to de-trend it, filtering with an adaptive band pass filter around the ventilation frequency, and computing PPV using a window length aligned with the ventilation cycle to suppress noise and irregularities, thereby improving the accuracy and reliability of PPV calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PPV algorithms are used to calculate pulse pressure variation, then the calculation can be performed continuously, but the results are unreliable due to baseline changes, irregular heartbeats, and varying phases between cardiac and ventilation cycles
Solution Approach 1:
The patent applies preliminary action by detecting gain changes and excessive baseline modulations before PPV calculation to identify and exclude unreliable signal portions. This advance detection prevents contaminated data from entering the PPV computation, thereby improving both reliability and precision of the final PPV values.
Solution Approach 2:
The system implements feedback by continuously monitoring signal quality metrics (gain changes, baseline modulations) and using this information to adjust which portions of the physiological signal are included in PPV calculations. This closed-loop approach ensures that only reliable signal segments contribute to the final PPV value, resolving the contradiction between continuous calculation and result reliability.
2Quantity of substance
If all portions of the physiological signal are used for PPV calculation, then more data is available for computation, but falsely elevated or diminished PPV values occur due to hemodynamic changes and irregular heartbeats
Solution Approach 1:
The patent extracts and removes harmful components from the physiological signal by detecting gain changes and excessive baseline modulations. By identifying and excluding signal portions affected by hemodynamic changes, irregular heartbeats, or other artifacts, the system retains only the reliable portions for PPV calculation, thus maintaining data quantity while improving reliability.
Solution Approach 2:
The system changes the parameter of signal selection by dynamically adjusting which portions of the physiological signal are included in PPV computation based on detected signal quality. When gain changes or excessive baseline modulations are detected, the corresponding signal portions are excluded, effectively changing the composition of data used for calculation to improve reliability.
3Measurement precision
If post-processing is applied to correct falsely elevated or diminished PPV values, then some accuracy can be improved, but the complexity of the algorithm increases and may introduce delays
Solution Approach 1:
The patent applies preliminary action by performing signal quality assessment and exclusion of unreliable portions before PPV calculation, rather than requiring complex post-processing. This proactive approach simplifies the overall algorithm by preventing contamination at the source, thereby improving precision without significantly increasing complexity.
Solution Approach 2:
The system introduces an intermediary step of signal quality detection that acts as a mediator between raw physiological signal and PPV calculation. This intermediary layer filters out unreliable data portions before they can affect the PPV computation, achieving accuracy improvement with minimal added complexity compared to complex post-processing approaches.
Data Source
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AI summary
The present invention relates to a device, system and method for determining pulse pressure variation of a subject. To enable more reliably determining pulse pressure variation of a subject the device comprises a signal input (11) configured to obtain an input signal representing a hemodynamic signal of the subject, a processor (12) configured to process the input signal and compute a pulse pressure variation and a signal output (13) configured to output the computed pulse pressure variation. The pulse pressure variation is computed by deriving a pulse height signal from the input signal, deriving a pulse height baseline and a de-trended pulse height signal from the pulse height signal as the ratio between the difference between extrema of the de-trended pulse height signal and the respective value of the pulse height baseline signal, and computing the pulse pressure variation from the de-trended pulse height signal and the pulse height baseline.