Inversion-Based Feed-Forward Control for Ventilator Synchrony
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Solution Overview
Problem
Modern ventilator control systems often fail to accurately match desired pressure and flow waveforms due to variations in patient and device characteristics, leading to sub-optimal patient-ventilator synchrony and increased patient work of breathing.
Innovation Solution
The implementation of an inversion-based compensatory feedforward control scheme that calculates additional flow commands based on estimated hardware and patient characteristics, enhancing closed-loop control performance by providing supplemental support to the primary controller, thereby improving response time and synchrony.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed-loop control is used to regulate breathing gas flow rates, then the ventilator can respond to patient breathing needs, but delays and variations in pressure/flow waveforms occur due to circuit compliance, valve characteristics, and resistance
Solution Approach 1:
The patent applies preliminary action by calculating and applying compensation commands before the expected pressure/flow response occurs. The system computes compensation based on measured pressure deviations and known system characteristics (circuit compliance, valve characteristics, resistance) to preemptively correct for anticipated delays and variations in the pneumatic system response.
Solution Approach 2:
The patent employs feedback by continuously monitoring actual pressure waveform deviations from the desired reference trajectory and using this information to compute real-time compensation commands. The compensation is calculated based on the measured pressure error and system characteristics, creating a closed-loop correction mechanism that improves synchrony while compensating for system delays.
2Ease of operation
If standard closed-loop control is used, then basic ventilation support is provided, but patient work of breathing increases due to sub-optimal pressure tracking
Solution Approach 1:
The patent applies preliminary anti-action by calculating compensation commands that counteract expected pressure tracking errors before they significantly impact patient breathing. The system uses knowledge of system characteristics (circuit compliance, resistance, valve dynamics) to predict and compensate for pressure deviations, thereby reducing the additional work the patient must perform to achieve desired breathing volumes.
Solution Approach 2:
The patent replaces pure mechanical/pneumatic control with a computational control mechanism. Instead of relying solely on the physical characteristics of valves and circuits to deliver the desired pressure waveform, the system uses real-time computation to calculate compensation commands that account for system imperfections, substituting computational precision for mechanical precision.
3Productivity
If existing control systems are used, then ventilation support is delivered, but performance is sub-optimal despite availability of patient and device characteristic information
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting control commands based on measured pressure deviations and known system parameters. The compensation calculation incorporates specific patient and device characteristics (circuit compliance, resistance, valve time constants) as input parameters to optimize the control response for each specific configuration, thereby improving performance without requiring hardware changes.
Data Source
AI summary
A ventilator and method of ventilator control. The ventilator includes a pneumatic system for providing and receiving breathing gas, and a controller operatively coupled with the pneumatic system. The controller employs closed-loop control to provide positive breathing assistance to a patient. Supplemental feed-forward compensatory assistance is also provided, in addition to and independently of that commanded by the closed-loop control. The supplemental assistance may be determined, set or selected based on a ventilator parameter and/or an operator parameter, and/or as an automatic ongoing compensatory mechanism responding to varying patient respiratory demand.