CPAP Pressure Control Using Flow-Rate Feedforward Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CPAP apparatuses struggle to maintain target air pressure despite disturbances caused by patient inhalation or exhalation, leading to inadequate airway opening during sleep.
Innovation Solution
The CPAP apparatus incorporates a control unit with a command generation unit, command correction unit, and flow rate measuring unit to adjust fan rotation based on real-time flow rate and pressure measurements, ensuring the air pressure reaches the target pressure despite respiratory disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure control is used to deliver air to the mask, then the airway can be opened, but the target pressure cannot be sufficiently compensated when patient inhalation or exhalation flow rate is large
Solution Approach 1:
The flow rate measuring unit measures the flow rate of air between the fan and the air passage member outlet in advance, and the command correction unit corrects the command value based on this measured flow rate before the pressure delivery is affected by patient respiration disturbances. This preliminary measurement and correction approach allows the system to anticipate and compensate for pressure variations caused by patient inhalation or exhalation, ensuring reliable target pressure compensation without requiring overly complex control mechanisms.
2Reliability
If the fan rotation is increased to compensate for pressure loss, then the target pressure can be maintained, but the energy consumption increases
Solution Approach 1:
The command correction unit continuously monitors the flow rate of air delivered to the patient and adjusts the fan rotation command value in real-time based on this feedback. When patient respiration causes increased air flow demand, the system detects this through the flow rate measuring unit and appropriately increases fan rotation to maintain target pressure. This feedback mechanism ensures that energy is consumed only when necessary to maintain pressure, rather than operating at maximum capacity continuously.
3Measurement precision
If real-time flow rate measurement is implemented, then pressure control accuracy is improved, but the device complexity increases
Solution Approach 1:
The flow rate measuring unit acts as an intermediary component that provides accurate flow rate data to the command correction unit, which then uses this information to adjust the fan rotation command. This intermediary measurement approach enables precise pressure control by providing the control system with accurate real-time flow rate information, allowing for accurate calculation of the command value needed to maintain target pressure without requiring complex direct pressure sensing or control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively maintains target air pressure, ensuring consistent airway opening and ease of breathing for patients by compensating for respiratory fluctuations through both feedback and feed-forward control mechanisms.
Implementation Method 1
a fan (16) configured to expel air flowing in from the intake inlet (18), from another end of the air passage member (20)
Data Source
AI summary
A CPAP apparatus according to the present disclosure includes a housing, a hose whose one end communicates with a connection portion, a fan configured to expel air flowing in from an intake port, from another end of the hose, a motor and a motor driving unit configured to rotationally drive the fan, a control unit configured to control the motor driving unit, and a flow rate sensor. The control unit includes a command generation unit configured to generate a command value of a rotation number of the fan such that a pressure to be expelled from the other end of the hose becomes a target pressure, and a command correction unit configured to correct the command value based on a flow rate value obtained by the flow rate sensor.