Research And Implementation Of Distributed Blood Pressure Monitoring System

Cardiovascular diseases(CVDs)have been the leading cause of death in the world.It has been proven that early detection and timely control of CVDs could be achieved through continuous long-term health monitoring.Therefore,the research of continuous physiological monitoring system has become the focus of people all over the world.With the development of mobile communication technology and micro-sensor technology,wearable devices have demonstrated their strong development potential in the field of healthcare.At present,wearable detection devices for physiological signals such as Electrocardiograph(ECG),PhotoPlethysmo Graphy(PPG)and blood oxygen have been widely accepted.However,its monitoring function is still far from the level that can achieved disease prevention.On the one hand,the devices function is too simple to support the need for disease diagnosis;on the other hand,research on wearable medical equipment is still in its infancy that there have no perfect digital standards for disease diagnosis by wearable equipment.With the advancement of the medical device manufacturing process,feature wearable medical methods combined with 5G and emerging internet technologies would greatly enhance the flexibility of therapeutic services and alleviate the uneven distribution of medical resources.Continuous blood pressure(BP)measurement is the most common method for clinical diagnosis of CVDs.Aiming at the problem of continuous circadian BP monitoring,a wearable and low-disturbance human BP monitoring system is designed in this dissertation.The implementation of the system is based on distributed wearable devices and wireless communication technologies: a PPG acquisition equipment,an ECG acquisition equipment and an Android smart phone constitute the hardware platform while the Bluetooth Low Energy technology is used as communication method for different hardware nodes.In view of the problem of clock unification in distributed systems,the time delay distribution in Bluetooth links is analyzed and a time synchronization method based on probability is proposed,which ensures the synchronization of PPG and ECG,and thus improves the measurement accuracy of pulse transit time(PTT).The BP estimation is achieved in a non-invasive way.Specifically,the traditional BP model based on PTT is described in this dissertation while a BP model based on slope transit time(STT)is proposed as an alternative model under the circumstances of insufficient PTT accuracy and possible synchronization failure.The STT factor in this scheme relies only on single PPG signa,avoiding the problem that the blood pressure cannot be estimated due to signal out-synchronization,and therefore has better stability than the PTT-based BP model.After testing,this study verifies the stability and accuracy of PPG and ECG acquisition and processing,time synchronization algorithm and BP estimation algorithm.And the clock deviation can be controlled within 4 ms,the systolic BP estimation error is 1.78 ?5.30 mm Hg while the diastolic BP estimation error is 0.71?3.56 mm Hg.The overall system runs smoothly and reliably,proving it to be a promising prototype for a cuff-less sphygmomanometer.