| As a primary vital sign parameter,blood pressure is one of the essential monitored factors in clinic,which aims to provide some significant reference data for disease diagnosis,therapeutic efficacy observation and prognosis judgment.Nowadays,arteriopuncture catheterization(also be called invasive catheterization)is the most commonly used way to measure blood pressure in such medical centers as operating rooms and ICUs(intensive care unit),it may cause some damage to patients' bodies,leading to hemorrhage or infection at the treatment parts,and it is also a demanding task for the doctors with complicated operation process.What is more,specialized equipment is also needed.Therefore,relative to invasive arterial blood pressure monitoring,noninvasive,continuous,real-time monitoring of blood pressure is safe,convenient,low infection rate,can give doctors and patients with great convenience.The non-invasive and continuous blood pressure monitoring system apply the applanation tonometry measuring method into designing and completing.To be specific,this system is comprised of upper and lower computers.During the process to accomplish this system,this thesis mainly sets out to fulfill the task of designing and completing the varied functions for lower computers.Details will be presented as follows:1.As for the collection of blood signals,this monitoring system has amplified and filtered these signals through hardware circuit and,then,collected the data by using SCM(signal chip microcomputer).At the same time,it has made further efforts to filter the external disturbing factors with varied digital filter algorithms.(1)For the interference produced by accidental factors,this thesis,by combining the advantages of median filter algorithm and weighted average filter algorithm,writes a program to form a median weighted average filter algorithm.This new algorithm can filter the vibration caused by impulse interference,control the noises made by electronic parts and also improve this monitoring system's sensitivity for the selected sample values.(2)A 10-order FIR low-pass filter algorithm is implemented for the burr spikes and high frequency interference of arterial pressure waveforms.The algorithm can further filter out the external disturbances introduced during signal acquisition.2.By applying the applanation tonometry measuring method,this thesis uses the servo control project to automatically locate the body parts with highest pulse pressure using pressure sensor(the artery blood vessels are flat-shaped).To start with,this thesis sets out to design a mechanica l fixing device for the use of fixing pressure sensors and establish a hardware control platform.Then,by using STM 32,the SCM is programmed to sent PWM signal in order to control this servo to drive the pressure sensor and find the spot with highest blood pressure.Significantly,the optimization algorithm is also worked out which can accurately calculate the blood pulse pressure.3.It has realized the exchange between two different measured parts.This thesis has firstly designed a improved exchange project,only taking two STM32 SCMs to achieve this function.By designing a serial communication program within SCM serial port function is worked out and it also accomplish the communication between upper computer and SCM,SCM and SCM.After taking a series of functional tests,the varied modes in non-invasive continuous blood pressure monitoring system are proved to be accurate and stable.And they do successfully monitor human's blood pressure constantly and with out invasion,thus this project's purpose is fully accomplished.In the end,this thesis carries out a comparative experiment for blood pressure by using this monitoring system and electronic sphygmomanometer,the experimental results verify the system to monitor the correctness of human blood pressure values. |
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