CPAP Adapter Flow Calculation for Oxygen and Tidal Volume
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Solution Overview
Problem
Existing respiratory assist devices, such as CPAP systems, lack the capability to accurately determine the total flow output and the amount of oxygen inhaled by a patient, making it difficult for clinicians to monitor patient tidal volume effectively.
Innovation Solution
A system comprising a flow generator connected to a patient interface with a pressure sensor and an oxygen input line, utilizing a controller to calculate total flow output based on patient interface pressure and oxygen input line flow, and accounting for leak flow during exhalation pauses to determine patient tidal volume and oxygen concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CPAP system is used to deliver breathable gas to a patient, then the airway is kept open during inhalation, but the system cannot determine the total flow output or the amount of oxygen inhaled by the patient
Solution Approach 1:
The patent introduces a flow generator as an intermediary device between the oxygen source and the patient interface. This flow generator includes a controller that calculates total flow output by combining measured oxygen input flow with estimated ambient air entrainment based on patient interface pressure. This intermediary device enables measurement capabilities without requiring direct instrumentation in the patient breathing path, thus resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent replaces direct mechanical flow measurement devices with a computational approach. Instead of using complex flow meters throughout the system, the controller uses pressure sensors and known flow characteristics to calculate total flow output through mathematical relationships. This substitution of mechanical measurement systems with computational methods reduces device complexity while maintaining measurement precision.
2Reliability
If clinicians need to monitor patient tidal volume effectively, then accurate measurement of oxygen inhaled is required, but existing respiratory assist devices lack this capability
Solution Approach 1:
The flow generator serves multiple functions: it delivers breathable gas to the patient, measures oxygen input flow, senses patient interface pressure, calculates total flow output, and determines oxygen concentration inhaled. By making the flow generator a multi-functional device, the system achieves reliable patient monitoring capabilities without adding separate dedicated devices, thus resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The system implements feedback by continuously measuring patient interface pressure and using this information to adjust and refine the calculation of total flow output and oxygen concentration. The controller uses real-time pressure data to estimate ambient air entrainment and update flow calculations dynamically, providing reliable monitoring feedback to clinicians while maintaining system simplicity.
Data Source
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AI summary
A system for determining total flow output from a flow generator (14), and/or tidal volume of gas inhaled by a patient includes: - the flow generator for connection to a patient interface (18); - a patient pressure sensor (22) to measure patient pressure at the patient interface and an oxygen input line with an oxygen input line sensor (35), both in communication with a controller (40) including a processor. The oxygen input line conveys oxygen from an oxygen source (44) to the flow generator, and has an oxygen control valve (31) for controlling the flow of oxygen from the oxygen source to the flow generator. The processor is programmed with one or more algorithms to determine the flow output for the flow generator based on a particular patient pressure and oxygen input line flow. Leak flow is subtracted from the flow generator output to determine patient flow, which is integrated to calculate patient tidal volume of gas inhaled.