Dual Pressure Sensor CPAP System Exhalation Phase Control
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Solution Overview
Problem
Current CPAP therapy systems cause discomfort due to excessive pressure during the expiratory phase, as they often supply constant positive pressure regardless of the breathing cycle, leading to resistance and discomfort for patients with obstructive sleep apnea.
Innovation Solution
A CPAP system utilizing dual pressure sensors at the source and on a ventilation mask to control an exhalation valve, regulating therapeutic airflow based on pressure differentials between mask pressure and blower pressure, providing pressure relief during exhalation by reducing airflow accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant positive pressure is supplied during the entire breathing cycle, then airway splinting during inspiration is maintained, but patient comfort during expiration deteriorates due to excessive pressure resistance
Solution Approach 1:
The system dynamically adjusts the positive pressure level based on the detected breathing phase. During inspiration, full CPAP pressure is maintained to splint the airway open. During expiration, the system automatically reduces pressure to minimize resistance and discomfort. This dynamic adaptation resolves the contradiction by making pressure delivery responsive to physiological needs rather than static.
Solution Approach 2:
The system employs flow sensors and pressure sensors to continuously monitor the patient's breathing cycle and provides feedback to the pressure control mechanism. Based on this feedback, the system detects phase transitions between inspiration and expiration and adjusts pressure accordingly. This closed-loop feedback ensures airway splinting during inspiration while preventing excessive pressure during expiration.
2Reliability
If pressure augmentation is applied throughout the breathing cycle, then airway patency is maintained, but energy efficiency deteriorates due to unnecessary pressure delivery during expiration
Solution Approach 1:
The system applies pressure augmentation periodically rather than continuously, synchronizing pressure delivery with the inspiratory phase of the breathing cycle. During expiration, pressure augmentation is reduced or suspended. This periodic action pattern matches the physiological demand for airway support, maintaining patency when needed while eliminating energy waste during phases when the airway naturally remains open.
3Device complexity
If single pressure sensor at blower output is used, then device complexity is reduced, but measurement precision deteriorates due to inability to detect actual mask pressure
Solution Approach 1:
The system uses a pilot line as an intermediary conduit that connects the mask interior to the pressure sensor located at the blower output. This pilot line transmits the actual mask pressure to the sensor without requiring the sensor to be physically positioned at the mask, thus maintaining measurement precision while avoiding the complexity of multiple sensors or complex sensor positioning.
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
This approach optimizes patient comfort by dynamically adjusting pressure according to the breathing cycle, reducing discomfort and improving the effectiveness of CPAP therapy by minimizing unnecessary pressure augmentation during exhalation.
Implementation Method 1
a first pressure sensor that can measure a mask pressure in the patient ventilation interface
Implementation Method 2
a second pressure sensor that can measure a blower pressure at the output of the blower
Implementation Method 3
The pressure controller can regulate therapeutic airflow delivered to the patient and exhausted through the piloted exhalation also based upon such pressure differentials
Implementation Method 4
a blower with an output... A gas passage conduit that couples the output of the blower to the patient ventilation interface
Data Source
AI summary
A continuous positive airway pressure (CPAP) apparatus for respiratory assistance of a patient is disclosed. There is a blower having an output connectible to a ventilation mask wearable by the patient. A first pressure sensor measures blower pressure at the output of the blower, and a second pressure sensor that is connectible to the ventilation mask measures mask pressure therein. A pressure controller is connected to the first pressure sensor and the second pressure sensor, and a patient inspiratory phase and a patient expiratory phase is be detectable by the pressure controller to regulate therapeutic airflow delivered to the patient based upon pressure differentials between the mask pressure and the blower pressure.