Projects:2018s1-157 Designing Airway Pressure Control Technology for Sleep Apnea Treatment
Mike Tanggie Bilang
Associate Professor Mathias Baumert
The aim of this project is to design novel technology for controlling mask pressure adaptively, by incorporating physiological signals in the control algorithm. The novel technology includes intelligent control logic, the intelligent control system need to able get feedback from patient, at the same time analysis the received information, then implement the most suitable treatment for patient in order to prevent sleep apnea happen. The control system need physiological signals and these can be achieved by different kind of sensors. In this project, heart rate/pulse oximetry sensor and blood oxygen saturation sensor has been decided to use.
Enhance the functionality of the CPAP machine
- The existing CPAP machine will be added with two new sensors, which are the blood oxygen saturation and the heart rate/pulse oximetry sensor.
- The machine's circuitry and functionality will be further analysed to implement the new sensors.
- The control logic to integrate the sensors with the machine is designed.
Ensure the compatibility between the machine and sensors implemented
Incorporate physiological signals in the machine's control logic
Figure 1 shows the system overview for the control system. The control system consists of the touch screen monitor, the Arduino UNO board, the heart rate and pulse oximeter sensor, the pressure sensor, the motor driver evaluation board (DRV8312 EVM), the blower assembly (pump), and the air tube. The touch screen monitor will display the value of the air pressure, the motor speed, and the heart rate and the blood oxygen saturation. The Arduino UNO board will collect the data in the form of analog signals from the two sensors. The data will be collected in the following precedence, firstly the air pressure, next data is the blood oxygen saturation, and lastly the heart rate. The heart rate and pulse oximeter sensor (pulse rate sensor) will measure the heart rate, the pulse rate, and the blood oxygen saturation. The code is program to measure all the values and display them on the touch screen. The pressure sensor will measure the air pressure and display the value on the touch screen. The motor driver evaluation board will drive the three-phase brushless DC (BLDC) motor. It will control the motor speed based on the data collected by the Arduino UNO board. The PID system control logic is used to enable the evaluation board controlling the speed of the motor by considering the data from the sensors as the input. The microcontroller unit (MCU) of the Arduino UNO board is able to adjust the operation in real time so that the airflow is maintain in settling level. The pump will provide the pressurised air to the patient via the air tube. The air pressure value will indicate the condition of the patient. If the pressure is high, the patient is possibly under the sleep apnea condition. The heart rate and blood oxygen saturation show the event of asphyxia. Meanwhile, the pulse rate and the blood oxygen saturation are unable to predict the worst event of sleep apnea due to a delay on the signal.
During the completion of this project, it is found that the touch screen monitor is unable to read the data from the pulse rate sensor. This happened because the Arduino UNO MCU is unable to read the incoming signals from the sensor. On the positive side, the monitor is able to read the data of the air pressure sensor. Besides that, the evaluation board is not communicate with the MCU which means that the motor driver is unable to be controlled based on the physiological signals. Therefore, the experimental CPAP machine is not able to work as expected.
In the future, the Arduino MCU should be implemented to read signals from more than one sensor. This means that the scope of the physiological signals that will be implemented as the input for the machine should be expand. The project can include the blood pressure as the new physiological signal to control the CPAP machine.