Dynamic Threshold Curve for Ventilator Phase Transitions
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Solution Overview
Problem
Conventional ventilator machines face challenges in achieving accurate synchronization between patient breathing activity and ventilator assistance, particularly in neonates and COPD patients, due to interference in electromyographic signals, leading to incorrect or late detection of breathing phases and increased respiratory effort.
Innovation Solution
A dynamic threshold curve is implemented for ventilator phase changes, with high initial values during refractory periods that gradually decrease or increase to target thresholds based on expected phase durations, ensuring precise timing for inspiration and expiration transitions, reducing incorrect changeovers and improving synchrony.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold is used for triggering breaths based on EMG signals, then the triggering mechanism is simple to implement, but it leads to auto-triggering or delayed triggering due to signal interference and disruptions
Solution Approach 1:
The patent implements a dynamic threshold that varies over time during the respiratory cycle, transitioning from a higher threshold during expiration to a lower threshold during inspiration. This dynamic adjustment allows the system to adapt to the natural variability of EMG signals while maintaining reliable breath detection, resolving the contradiction between simple implementation and accurate triggering.
Solution Approach 2:
The patent changes the threshold parameter based on the detected phase of the respiratory cycle. By adjusting the threshold level according to whether the system is in inspiration or expiration phase, the patent achieves reliable breath triggering despite signal interference, while keeping the overall mechanism relatively simple through parameter adaptation rather than complex algorithms.
2Reliability
If filtering is applied to prevent interference in EMG signals, then signal reliability improves, but additional delay is introduced to the signals
Solution Approach 1:
The patent applies filtering and signal processing in advance, during the expiration phase when breath triggering is less critical. This preliminary processing prepares the signals for accurate detection during the subsequent inspiration phase without introducing critical delays at the moment of triggering, as the filtering is already complete by the time triggering is needed.
Solution Approach 2:
The patent uses a dynamic threshold approach that compensates for any delays introduced by filtering. By adjusting the threshold over time based on the expected timing of breaths, the system accounts for processing delays and ensures accurate triggering despite the time loss from signal filtering.
3Measurement precision
If a dynamic threshold varying over time is implemented, then breath triggering accuracy improves, but the control mechanism becomes more complex
Solution Approach 1:
The patent implements a periodic dynamic threshold that follows the natural rhythm of the respiratory cycle. The threshold oscillates between higher and lower values in sync with expiration and inspiration phases, providing accurate breath detection through a relatively simple periodic pattern rather than complex adaptive algorithms.
Solution Approach 2:
The patent uses feedback from the detected respiratory phase to adjust the threshold dynamically. The system monitors the current phase (inspiration or expiration) and automatically adjusts the threshold accordingly, creating a closed-loop control mechanism that improves precision while keeping the complexity manageable through phase-based control.
4Reliability
If the threshold is kept high during the entire respiratory cycle to prevent false triggering, then auto-triggering is reduced, but delayed or missed triggering of actual breaths increases
Solution Approach 1:
The patent employs a periodic threshold pattern that is high during expiration (when false triggering is more likely) and low during inspiration (when actual breaths occur). This periodic variation maintains reliability by preventing false triggers during expiration while ensuring timely detection of actual breaths during inspiration.
Solution Approach 2:
The patent changes the threshold parameter based on the respiratory phase detected by the system. By switching between high and low threshold values according to whether the system is in expiration or inspiration phase, the patent simultaneously achieves false triggering prevention and timely breath detection without compromise.
Data Source
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AI summary
The present invention relates to the automatic control of a ventilator machine, for changing over between two alternating phases of ventilation by, in one phase of ventilation, causing a control unit to examine a sensed respiratory signal for breathing activity (μV) for a threshold criterion (2) for the changeover to the next phase of ventilation. There is in an expiration phase, for the changeover to an inspiration phase, a dynamic threshold curve, and there is in an inspiration phase a dynamic threshold curve, and a changeover is made when the signal for breathing activity threshold curve is crossed. The durations of the inspiration and expiration phases or the duration of a breath (an inspiration and an expiration phase) are each stored and the expected times of the maximum phase durations are derived from the distributions of the phase durations.