Development And Research Of Electrohysterogram Signal Monitoring System

Uterine contraction is an important clinical indictor for monitoring uterine activity.Electrohysterogram(EHG)is a signal of pregnancy uterus electrical activity recorded from the abdominal surface in a pregnant woman.It can truly reflect the uterine contraction.Therefore,EHG signal is expected to be a diagnostic indicator for identifying contractions and predicting preterm birth.However,previous studies about the analysis of EHG signals were based on various signal collection devices.At present,there is no instrument in the market dedicated to collect EHG signals.Therefore,this study is aimed at designing a small,portable instrument to record EHG signals.And the performance of instrument was validated by laboratory test and analysis of clinical data.First,according to the low frequency and amplitude characteristics of EHG signals,this study designed a low power instrument to collect EHG.The EHG monitoring system consisted of 8 electrodes and a TOCO,a signal acquisition module,the firmware in microcontroller,and the software in personal computer(PC).The PC software controlled the instrument through Bluetooth,and recorded the EHG signal of 8 channels,the TOCO signal and the marking signal of the pregnant woman's self-perception.The instrument could collect EHG signals in real time,display and store signals synchronously on the PC software.Secondly,the performance tests of the instrument,including calibration of the contraction pressure,repeatability,stability and consistency experiments,were designed.The results show that the electrical signal(m V)was converted to pressure signal(mm Hg)by calibration.Besides,the repeatability,stability and consistency of the prototype were good,which provided support for later experiments.Then,according to the actual situation,the noises genetrated in the process of signal acquisition were summarized,and the denoising algorithm was studied.The EHG signals and noise signals were simulated and mixed.The denoising algorithm was studied by mix signals in the simulation.The empirical mode decomposition combined with the wavelet transform were used to study the denoising effect for superimposed signals.The results were evaluated by the intuitive graph,and the calculation of the signal-to-noise ratio(SNR)and the root mean square error(RMSE).The results show that the denoising effect of the empirical mode decomposition combined with the wavelet transform was superior to other common denoising methods.Finally,to verify the accuracy of the EHG monitoring system in clinical application,an experiment of EHG signals collection was designed.Suitable pregnant women were chosen for EHG signal acquisition.From 2017 to 2018,a total of 171 cases of labor data were collected,28 cases of premature signals were collected.The study about denoising algorithm was based on the actual collected signals.The denoising results showed that the instrument can effectively record the EHG signals without distortion.The application of the denoising algorithm could visually present the waveforms of the EHG signals.In summary,the EHG recording system is capable of reliably recording EHG signals.It has the advantages of portability,low power consumption and wireless transmission.For clinically acquired signals,a simple denoising method can be used to visually present the burst wave signal,which can be used for subsequent EHG signal algorithm research.In the futher,the instrument could be widely used in clinical and family.