Nitric Oxide Delivery Apparatus Adaptive Control
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Solution Overview
Problem
Current nitric oxide delivery systems face challenges in maintaining a proportional and consistent delivery of NO gas due to limitations in dynamic range and flow control, especially at extreme flow rates, leading to potential shutdowns and adverse patient outcomes such as rebound hypertension and oxygen desaturation.
Innovation Solution
An apparatus and method that include a control circuit with flow sensors to measure breathing and therapeutic gas flows, calculating and displaying a calculated dose of nitric oxide, and providing alerts and adjustments to maintain a stable delivery, even at varying flow rates, using a CPU and clinical decision support software to prevent shutdowns and ensure accurate NO delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If proportional flow control is used to deliver nitric oxide, then the desired dose can be titrated, but the system under-delivers at extreme flow rates (lower than 1% or greater than 100% of control range)
Solution Approach 1:
The patent implements dynamic adaptation of control parameters based on operating conditions. The system adjusts the proportional gain and integral action of the PID controller according to the current flow rate, allowing optimal performance across the entire dynamic range from very low to very high flows. This resolves the contradiction by making the control system adaptable rather than fixed, enabling accurate dose delivery at all flow rates including extremes.
Solution Approach 2:
The system changes control parameters (PID gains, valve positioning) based on the operating point. When flow rates move outside the optimal 1-100% range, the controller dynamically adjusts parameters to maintain proportional accuracy. This parameter adaptation allows the system to deliver accurate NO doses regardless of whether the patient is in gentle ventilation (low flow) or conventional ventilation (high flow).
2Measurement precision
If PID control with electromagnetic valve and flow sensor is used, then proportional flow control is achieved, but integral error is minimal to drive sufficient control system proportional valve gain at lower 1% end
Solution Approach 1:
The control system dynamically adjusts the proportional gain based on the operating point. At very low flows (lower 1% end), the system increases proportional gain to compensate for minimal integral error, ensuring the control valve has sufficient drive to achieve accurate positioning. This dynamic adjustment resolves the contradiction between measurement precision and ease of operation by adapting the control characteristics to match the operating conditions.
3Measurement precision
If highly tuned proportional control with fast response is used, then control accuracy improves, but system may over-deliver dose when operating in lower 1% of control range due to hysteresis or poor valve acting
Solution Approach 1:
The system uses feedback from the flow sensor to continuously monitor actual NO delivery and adjust the control valve positioning accordingly. This closed-loop feedback compensates for hysteresis and poor valve acting characteristics, ensuring consistent dose delivery even at very low flows where over-delivery risks exist. The feedback mechanism resolves the contradiction by providing real-time correction rather than relying solely on open-loop control tuning.
Solution Approach 2:
The control system applies partial action by using integral control to accumulate small errors over time, providing a gradual build-up of corrective action rather than immediate full correction. This prevents overshoot and over-delivery at low flows while still achieving the desired dose through sustained partial adjustments, resolving the reliability issue associated with highly tuned proportional control.
4Reliability
If delivery apparatus shuts down automatically when calculated ratio-metric NO flow exceeds limits, then delivery safety is maintained, but patients experience adverse effects such as worsening PaO2 and increasing PAP
Solution Approach 1:
The system dynamically adapts to varying patient needs and flow conditions rather than using fixed shutdown thresholds. By continuously adjusting control parameters and maintaining proportional accuracy across the full dynamic range, the system can safely deliver appropriate doses even during gentle ventilation or other variable flow conditions that would previously trigger shutdowns. This eliminates the harmful rebound effects while maintaining safety through intelligent adaptation.
Solution Approach 2:
The control system changes operating parameters to match patient requirements in real-time. When flow conditions change (such as during gentle ventilation), the system adjusts its control strategy and parameter settings to maintain safe and effective NO delivery without triggering unnecessary shutdowns. This parameter adaptation resolves the contradiction by making safety dependent on actual delivery accuracy rather than fixed flow thresholds.
5Adaptability or versatility
If current inhaled NO delivery systems are used with gentle ventilation, then lower flows are required, but systems shut down due to insufficient dynamic delivery range
Solution Approach 1:
The system is dynamically designed to accommodate the full spectrum of ventilation strategies from conventional to gentle ventilation. By implementing adaptive control that adjusts to varying flow rates and patient needs, the system maintains reliable continuous delivery across all ventilation modes without triggering shutdowns. This dynamic capability resolves the contradiction by making the system versatile enough for gentle ventilation while maintaining delivery reliability.
Data Source
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AI summary
Described is an apparatus for monitoring nitric oxide delivery, wherein such apparatus comprises a display that provides a visual and/or numeric indication of the calculated dose of nitric oxide. Also described is a method of monitoring nitric oxide delivery, wherein the breathing gas flow rate and therapeutic gas flow rate are measured and used to determine the calculated dose of nitric oxide, which is then displayed. In some embodiments, an alert is provided when the calculated dose rises above or falls below a predetermined level or range.