Dual Flow Sensor Monitoring for Anesthetic Machine Accuracy
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Solution Overview
Problem
Existing methods for monitoring and controlling flows in anesthetic machines and ventilators fail to ensure accurate and safe mechanical ventilation due to deviations in flow measurements, which can be caused by sensor inaccuracies or changes in inhalation valve characteristics, leading to potential patient safety risks.
Innovation Solution
Installing flow sensors both inside the anesthetic machine or ventilator and in the patient's breathing circuit, with a microprocessor comparing the measured values to the characteristic curve of the inhalation valve to detect sensor and valve accuracy, allowing for accurate flow monitoring and compensation for deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow sensor is installed downstream of the Y-shaped connector in the patient breathing circuit for monitoring flow velocity, then the measurement accuracy is improved and the measured value is substantially equal to the gas flow delivered into the patient's lungs, but the flow sensor is easily affected by secretions of the respiratory tract and water vapor condensate causing measurement deviation
Solution Approach 1:
The patent divides the flow monitoring function into two separate locations: a first flow sensor in the equipment end (anesthetic machine/ventilator) and a second flow sensor in the patient end (breathing circuit). This segmentation allows each sensor to operate in its optimal environment - the equipment end sensor monitors dry gas flow while the patient end sensor monitors actual delivered flow, resolving the contradiction between measurement accuracy and sensor reliability
Solution Approach 2:
The patent introduces a microprocessor as an intermediary that receives signals from both flow sensors and performs comparative analysis. The microprocessor processes the flow data from both locations, identifies deviations caused by secretions or condensate at the patient end, and compensates for these effects, thereby maintaining measurement accuracy while accounting for sensor reliability issues
2Reliability
If a flow sensor is installed inside the anesthetic machine following the inhalation valve for monitoring drive gas flow, then the measured value is free from influence of water vapor condensate and secretions, but the measured flow deviates from the actual ventilation volume due to leakage and compliance changes
Solution Approach 1:
The patent segments the flow monitoring system into two measurement points: one at the equipment end (anesthetic machine) and one at the patient end (breathing circuit). The equipment end sensor provides stable, condensate-free measurements of drive gas flow, while the patient end sensor provides accurate measurements of actual delivered flow. By combining both measurements, the system achieves both reliability and precision
Solution Approach 2:
The patent implements a feedback mechanism where the microprocessor continuously compares the flow measurements from both sensors. When a deviation is detected between the equipment end measurement and patient end measurement, the system uses this feedback to identify and compensate for leakage or compliance changes, thereby maintaining measurement accuracy while utilizing the reliability of the equipment end sensor
3Device complexity
If single flow sensor monitoring is used, then the device complexity is reduced, but the ability to detect sensor failure and ensure patient safety is compromised
Solution Approach 1:
The patent applies local quality by placing flow sensors at two distinct locations with different functional characteristics. The equipment end sensor provides stable baseline measurements, while the patient end sensor provides accurate delivered flow measurements. This localized differentiation allows the system to detect failures and maintain safety without requiring complex redundant systems throughout the entire apparatus
4Extent of automation
If closed-loop flow control is implemented using a single flow sensor, then the ventilation volume control is automated, but the system cannot determine the causes of deviation between measured and preset values
Solution Approach 1:
The patent segments the control information source into two independent flow measurements. By comparing the equipment end flow measurement with the patient end flow measurement, the system can determine whether deviations are caused by equipment issues (valve characteristics, leakage) or patient circuit issues (secretions, condensate). This segmented information approach maintains automation while preserving diagnostic capability
Solution Approach 2:
The patent implements enhanced feedback by having the microprocessor compare measurements from both sensors against the preset ventilation parameters. This dual-feedback system not only automates control but also provides diagnostic feedback about the source of any deviations, allowing the system to maintain both automation and information about deviation causes
Data Source
AI summary
A method and an apparatus for monitoring and controlling flows in medical equipment including an anesthetic machine and a ventilator for influencing a patient's respiratory system are disclosed. The apparatus includes a microprocessor and an airway system including drive gas conduits provided with an inhalation valve (2) and an exhalation valve (5) for gas discharging as well as a ventilator end flow sensor (3) for measuring the introduced or discharged drive gas flow through the valves. The airway system also includes patient end breathing tubing in which a patient end flow sensor (11) for measuring the patient's inspired and expired gas flow is provided. By comparing the measured values of the two flow sensors against the characteristic curve of the inhalation valve (2), the microprocessor can judge the operation states and accuracy of the respective flow sensors and the inhalation valve (2).