A cardiopulmonary resuscitation system based on single chip microcomputer

　　1 Introduction

　　众所周知，在几分钟内及时抢救危重急症、意外伤害导致的突发濒死病人，具有重要意义。采用传统的人工呼吸和胸外按压方法，常常由于按压部位不准、用力方法不对、按压深度掌握不好、按压频率不规律等因素，难以达到理想的效果，甚至造成骨折、气胸、血胸等严重的并发症，同时口对口进行人工呼吸也有可能在病人与救护者间传染疾病。因此，有必要研制抢救迅速、定位准确、按压适度的便携式智能型心肺复苏机。其及时性和准确性可以显著提高救治效果，较好地解决徒手心肺复苏存在的问题。目前国内应用最为广泛的是美国Michigan Instruments 公司的“萨勃”心肺复苏机，国内市场仍然没有国产的便携式心肺复苏机。本文介绍的就是一种以Cygnal单片机为控制核心的便携式智能心肺复苏系统。[1-4]

　　2. Composition of single-chip cardiopulmonary resuscitation system

　　The structure diagram of the system is:

　　In the figure, 1 is a ventilation catheter, 2 is an opening valve, 3 is a gas storage cylinder, 4 is a pressure regulating valve, 5 is a solenoid valve, 6 is a pressure sensor, 7 is a single-chip controller, 8 is a solenoid valve, 9 is a cylinder, 10 is a piston, 11 is a spring, 12 is a pressure head, 13 is a solenoid valve, and 14 is a solenoid valve.

　　The system workflow is as follows:

　　1. Set the microcontroller parameters through the touch screen: pressing pressure, pressing frequency;

　　2. Open valve 2 and inflate gas cylinder 3;

　　3. The pressure regulating valve 4 and the solenoid valve 5 are opened, and the cylinder 9 starts to inflate and press;

　　4. Does the pressure sensor 6 detect whether the cylinder pressure is reached? If not, continue to inflate;

　　5. When the pressure sensor 6 detects that the cylinder pressure reaches a preset value, the solenoid valve 5 is closed and the solenoid valve 8 is opened;

　　6. Exhaust cylinder 9, and then go to step 3 cycle;

　　In order to achieve the purpose of portability, the system uses high-pressure oxygen as power. It uses a double cylinder, one is a gas cylinder, and the other cylinder is equipped with a piston. The piston is pushed by gas to press the chest. Because there is a spring under the piston, the pressing depth and pressing pressure are adapted to each other. The deeper the depth, the greater the pressure. When the pressure in the cylinder reaches the preset value, the solenoid valve is opened to exhaust, thereby controlling the pressing pressure. The pressure regulating valve is controlled by a stepper motor to adjust the gas pressure of the cylinder. After the pressure regulating valve reduces the pressure, the gas pressure is high, and the cylinder with the piston is inflated quickly, otherwise it is slow. In this way, the frequency of pressing can be controlled. The cylinder has a baffle at the displacement of 50mm to prevent the piston from moving down, so that the cylinder wall shares part of the force. The maximum pressing depth is 50mm, which can effectively prevent the pressing depth from being too deep and causing rib fractures.

　　The oxygen discharged through the solenoid valve 8 is controlled by the opening and closing time of the solenoid valve 13 and the solenoid valve 14 according to the compression-to-breathing ratio of 5:1 [5]. When the solenoid valve 13 is opened and the solenoid valve 14 is closed, the trachea is ventilated, and the tidal volume can be controlled by an external air bag. When the solenoid valve 13 is closed and the solenoid valve 14 is opened, the oxygen is discharged into the atmosphere.

　　3 Hardware Design of Single Chip Microcomputer Control System

　　This system intends to use the C8051F020 microcontroller from the American CYGNAL company.