Flow Therapy Oxygen Valve Control for Stable Target FdO2
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Solution Overview
Problem
Current methods for controlling oxygen delivery in respiratory apparatuses are challenging due to the difficulty in manually maintaining a target fraction of delivered oxygen (FdO2), especially when the total flow rate is fluctuating.
Innovation Solution
A respiratory apparatus with an ambient air inlet, a supplemental gas inlet, a valve to control the supplemental gas flow, a flow rate sensor, and a controller that determines the target supplemental gas flow rate based on the total flow rate and adjusts the valve current using a valve model to maintain the target FdO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual control of supplemental gas flow is used, then device complexity is reduced, but manufacturing precision of target FdO2 cannot be maintained when total flow rate fluctuates
Solution Approach 1:
The system continuously measures the actual FdO2 using a gas composition sensor and compares it to the target FdO2. The controller automatically adjusts the supplemental gas flow rate based on the difference between actual and target values, forming a closed-loop feedback control system that maintains precision despite flow fluctuations
Solution Approach 2:
The system uses its own measured parameters (total flow rate, gas composition) to automatically adjust its operation. The controller calculates the required supplemental gas flow based on measured values and self-regulates without external intervention, enabling the system to maintain target FdO2 autonomously
2Manufacturing precision
If automatic control with continuous valve adjustment is implemented, then target FdO2 precision is improved, but use of energy increases due to continuous valve model calculations and measurements
Solution Approach 1:
The system performs full valve model calculations and gas composition measurements only when necessary to correct FdO2 deviations, rather than continuously at maximum frequency. The controller adjusts the measurement and calculation frequency based on the magnitude of deviations and system state, reducing energy consumption while maintaining control precision
Solution Approach 2:
The system implements periodic gas composition measurements and valve adjustments rather than continuous operation. The controller cycles through measurement and adjustment operations at optimized intervals, allowing the system to maintain target FdO2 precision while reducing the average energy consumption of sensors and processors
3Ease of operation
If a coarse controller is used to iteratively increase valve current, then ease of operation is improved for initial valve opening, but loss of time occurs during the iterative process before flow is detected
Solution Approach 1:
The system uses a coarse controller as an intermediary to initially open the valve by iteratively increasing current until flow is detected. Once flow is established, control is transferred to the main controller which uses precise valve model calculations. This intermediary approach simplifies the challenging task of initiating flow from a closed state while minimizing overall response time
4Manufacturing precision
If the valve model is continuously updated with measured FdO2 and flow rate, then manufacturing precision of target FdO2 is improved, but use of energy and processing time increase due to continuous model updates
Solution Approach 1:
The valve model is updated with measured FdO2 and flow rate data at selective intervals rather than continuously. The system performs full model updates when significant deviations are detected or at scheduled intervals, while using cached model parameters for intermediate adjustments, reducing processing time while maintaining precision
Solution Approach 2:
The valve model is pre-calculated and stored with anticipated operating conditions and parameters. During operation, the system retrieves and applies pre-computed model parameters rather than performing full calculations in real-time, enabling rapid response while maintaining control precision through periodic updates with actual measurements
Data Source
AI summary
The present disclosure provides for a control system for a flow therapy apparatus. The control system can control delivery of a fraction of delivered oxygen (FdO2) to a patient. The control system can maintain the FdO2 at a target level during a therapy session. The control system can automatically control an oxygen inlet valve in order to control the flow of oxygen to the patient.