| Objective:In recent years, cardiovascular and cerebral vascular diseases were supposed to be high incidence, subsequently, along with that cardiac disease has been becoming a major killer to human health, such as sudden cardiac arrest, with its high prevalence and randomness of occurrence time and place, mostly outside the hospital. Timely and effective cardiopulmonary resuscitation (CPR) is the only opportunity for the survival of the patients. And chest compression as a significant part of the CPR is the key and central step of the basic life support (BLS), and even in many cases, the only technical mean. However, converging clinical researches revealed that the majority of cardiac arrest cases occurred out hospitals, with the most eyewitnesses being non-professional clinicians. The amateur rescuers often do not experience how to perform CPR, wasting the first aid opportunity, or they could not perform efficient CPR or even totally bad CPR, mainly inappropriate compression depth, compression speed, bad posture or non-full rebound. Even professional clinicians could not perform efficient CPR for the cardiac arrest occurred in the hospitals. Therefore, it is warranted that developing a real-time detect the CPR parameters (eg. compression depth, compression force, speed, vertical compression) technic for manual CPR. The CPR guidance technic could be promoted to out hospital community for whole people CPR training, this may greatly improve basic life support for the patients, which is crucial to the patients’survival rate. Meanwhile, the CPR guidance technic can be used to guide manual CPR in the hospitals while the automated CPR equipments are not timely assembled.Methods:The present study will focus on exploring a lightweight portable manual chest compression guidance instruments, specifically, concentrated on the chest compression depth, vertical compression, compression frequency detection and alarm. The study abandoned the conventional displacement sensors, such as electronic ruler, Hall sensor and ultrasonic sensor, and sought an indirect method: acceleration-displacement double integration, in other words, converting the compression acceleration to compression displacement through double integration. Secondly, the author investigated the integration reset mechanism based on compression force to solve the integration drift. The compression pressure point up to a prior threshold represents starting integration point and the pressure up to the maximum point represents the deepest compression and ending point of integration. The integration error was further removed through software compensation after integration reset. To solve the tilt compression, the author set the accelerometer sensitive axis to sample the gravity and further calculated the tilt angle according to the design principle of the inclinometer. While the tilt angle exceeds a preset angle, the tilt compression alarm mechanism would start. And finally, the present study designed compression metronome through voice guidance and LED flashing, to prevent low frequency compression.Contents:the main contents of present study include the following:Software algorithms:1、acceleration-displacement double integration algorithm. The present double integration mainly based on trapezoidal integration algorithm. The software design mainly included acceleration data acquisition, sampling time, acceleration data filtering.2、the present study investigated double integration drift and its possible affect factors through accessing to the large number of literatures, including:DC component, compression pressure-kinematic parameters asymmetry, time asymmetry of compression and rebound course, inconsistency of each compression starting position, tilt compression, environmental acceleration.3、integration reset mechanism based on compression pressure. The mechanism mainly consists of compression pressure acquisition, and recognition of starting compression point, the maximum depth compression and ending compression point based on compression pressure waveform. With respect to software design, it was implemented mainly through calculation of the slope rate of pressure waveform.4、tilt compression angle measurement. The accelerometer sensitive axis was set to acquire the gravity between the former compression ending point and the current compression starting point, and then the acquired gravity was averaged, subsequently, the tilt angle was computed through the three accelerations of corresponding axis divided by the gravity.Hardware design1、experiment platform:the author operated the compression experiments on two platforms:one is self-built manual compression platform integrated with electronic ruler and pressure sensor, the other is Anne Basic and SkillGuide. 2、compression acceleration acquisition:the present study systematically studied the characteristics of the ADXL345accelerometer, the acceleration module HQ7102and the matching circuit.3、pressure acquisition circuit:the present study used a pressure strain gauge for the compression pressure acquisition and built the corresponding filter, amplifier and AD converter circuits.4、other peripheral circuits:voice circuit, LED display for compression displacement as well as power circuit.Results:after several compression experiments and debugging on the Anne which has similar mechanical properties with human body, the final performance of the compression depth estimation is within0.6cm with95%confidence of a total of283compressions. And meanwhile, after tilt angle experiment on the self-built platform, the maximum error between the computed angle and the rotated gear on the platform was approximately2°, sufficient to meet the need of manual compression guidance.Conclusions:the present study provided an effective way for the application and promotion of the parameters-measuring technics of manual chest compression. The system could improve the quality and efficient of treatment for the cardiac arrest patient in the hospitals. Moreover, the system could improve the training effects of chest compression for non-professional clinicians. This would greatly improve the level of Chinese fist aid outside the hospitals. The out-hospital patients could get high quality of BLS until the arrival of emergency personnel, possibly, greatly improve the cardiac arrest patients survival rate. |
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