The Development Of Household Ventilator Based On μC/OS-Ⅱ And Embedded Linux

Obstructive sleep apnea syndrome (OSAS) is a common chronic sleep-related breathing disorder. Continuous positive airway pressure (CPAP) ventilator is the safest, most effective treatment method of OSAS. CPAP ventilator provides continuous positive airway pressure to the patient through the mask. It can prevent airway collapse, reduce or avoid snoring, hypopnea and apnea.Domestic research about household CPAP ventilator is still in its infancy and there is a wide gap compared with the developed countries. This paper refers to the development status of household ventilator, digital signal processing technology and embedded operating systems, and researches on the respiratory signal processing algorithm and telecommunications technology for household ventilator. This paper designs a household ventilator based on μC/OS-Ⅱ and embedded Linux.This paper studies on the structure and operation principle of home ventilator and analyze the control strategy and common parameters for household ventilator, determining main functions and technical indicators of the household ventilator. In order to achieve breathing signal real-time processing with data storage, remote communications, and touch-screen interactive features at the same time, the household ventilator uses dual-core design. The real-time control core uses microcontroller STM32F407 based on Cortex-M4 core and it runs the μC/OS-Ⅱ operating system. The telemedicine core uses microprocessor S3C2416 based on ARM9 core and it runs embedded Linux.This paper studies the digital filtering technology and breathing signal processing algorithms. This paper designs IIR digital filters to process the flow signal. The IIR low-pass filter is used to filter out high frequency noise in the flow signal and calculate the leakage. The IIR high-pass filter extracts the patient breathing flow from the total flow signal, and achieves breathing triggering. This paper identifies the technical specifications of the filters according to the human respiratory flow waveform characteristics. This paper designs function of the filter system with the help of MATLAB. By comparing flow waveforms before and after filtering, the paper verifies the filters’ performance. On the basis of the digital filtering technology, this paper studies respiratory signal processing algorithm and realizes key technologies like leak compensation, active pressure reduce function, apnea and hyponea detection.Real-time control core’s main functions are breathing signal real-time processing. Based on the real-time operating system μC/OS-Ⅱ, it realizes multi-task operation like pressure and flow sampling, continuous positive airway pressure controlling, leakage measurement, leakage compensation, breathing triggering, apnea and hyponea detection. Telemedicine core’s main functions are respiration data storage, telecommunications and human-computer interaction based on touch screen. This core runs multi-threaded application based on embedded Linux operating system. The application reads respiration data from the real-time control core and uses SQLite database to storage and query data. By using the Wi-Fi auto configuration technology, the ventilator can connect to Wi-Fi hotspot automatically. By establishing a TCP server, this core implements communications with the mobile client. This core also can connect to a remote server and upload treatment data. By connecting directly with remote medical professionals, it realizes remote diagnosis, treatment parameters modifying, and treatment plan downloading. It also achieves human-computer interaction based on touch screen with the help of Qt GUI framework.Experimental results show that the household ventilator fully combines the advantages of μC/OS-Ⅱ and embedded Linux operating system, and guarantees real-time performance of respiratory signal processing. It also improves the flexibility of data storage, communications and human-computer interaction, and implements telemedicine capabilities.