Gema Prats-Boluda

Effects of Configuration and Dimension of Concentric Ring Electrodes in EEnG Recording Applications.

Implementing Laplacian techniques through ring electrodes in bioelectrical records can improve the signal quality and spatial resolution in comparison to that obtained with conventional disk electrodes. Different dimensions of the rings and recording settings in one electrode can facilitate bioelectric mapping, and provide flexibility to studies in the field of bioelectrical signal recording. A concentric multi-ring electrode (multi-CRE), flexible, with gel, auto-adhesive, that can be configured for monopolar and bipolar records is presented in this paper. Simultaneous recording of intestinal myoelectric activity (electroenterogram, EEnG) by means of multi-CRE and conventional disk electrodes, respiration and electrocardiogram signals were performed in healthy subjects. The results revealed that the ability to detect intestinal slow waves was greatly influenced by the ability to reject its main interferences. Regarding the recording configuration, it can be concluded that the use of flexible concentric electrodes in bipolar configuration improves the quality of EEnG signals. Regarding to the effect of the electrode size, the middle ring (30 mm) reached a balance between better performance against respiratory interference of small rings and better response to low frequency interference of large rings.

Characterization of Uterine Response to Misoprostol based on Electrohysterogram.

When the maternal and fetal risks of prolonging gestation are higher than the benefits, labor induction is performed in order to stimulate uterine contractions and to facilitate cervical ripening. Nevertheless, not all cases end up in successful induction leading to an increase in the rate of caesarean sections. The aim of this study was to study the electrophysiological uterine response to misoprostol drug by obtaining and analyzing the evolution of temporal and spectral parameters from uterine electromyogram (electrohysterogram, EHG) records picked up during the first 4 hours of labor induction. Successful inductions showed a progressive increase in amplitude and a frequency shift in spectral content towards higher frequencies approximately 120 min after the initiation of labor induction; such response was not seen in failed inductions. In conclusion, the electrophysiological response caused by effect of misoprostol in pregnant women has been characterized by EHG parameters which showed patterns in their evolution that were different for successful and failed labor inductions. EHG recording and analysis could serve as a very helpful tool to predict the success of labor induction and hence reduce risks and facilitate labor management in this frequent clinical situation.

Electrohysterogram Signals from Patients with Threatened Preterm Labor: Concentric Ring Electrode Vs Disk Electrode Recordings.

Recording of electrohysterogram (EHG) has emerged as a non-invasive method for monitoring uterine dynamics during pregnancy. Usually EHG is picked up using conventional disk electrodes placed on the abdominal surface resulting in a limited spatial resolution due to the blurring effect of the volume conductor. In this respect, concentric ring electrodes have been proposed to pick up uterine myoelectrical activity in term patients so as to improve spatial resolution and to reduce physiological interferences embedded in these records. The aim of the present work is to check the feasibility of recording EHG signals using concentric ring electrodes (BC-EHG) in patients with threatened preterm labor and to compare their capability to discriminate true preterm labor from false alarms with that of conventional EHG bipolar recording. For this purpose, 50 sessions with simultaneous EHG recordings with conventional disk electrodes and concentric ring electrodes were conducted in 26 patients. Compared to conventional bipolar EHG recording, the BCEHG presents smaller amplitude and similar spectral characteristics. Statistically significant differences between women who delivered preterm and those that delivered at term were found for both the average peakpeak amplitude and the dominant frequency in the frequency range 0.2-1 Hz from BC-EHG recordings. Nonetheless no EHG parameter from simultaneous conventional bipolar recording showed statistically significant differences. These results suggest superior performance of BC-EHG recordings in patients with threatened preterm labor for discriminating true preterm labor from term labor.

Comparison of labour induction with misoprostol and dinoprostone and characterization of uterine response based on electrohysterogram

Abstract Objective: The objective of this study is to compare the uterine activity response between women administered dinoprostone (prostaglandin E2) and misoprostol (prostaglandin E1) for induction of labour (IOL) by analysing not only the traditional obstetric data but also the parameters extracted from uterine electrohysterogram (EHG). Methods: Two cohorts were defined: misoprostol (25-µg vaginal tablets; 251 women) and dinoprostone cohort (10 mg vaginal inserts; 249 women). All the mothers were induced by a medical indication of a Bishop Score < = 6. Results: The misoprostol cohort was associated with a shorter time to achieve active labour (p = .017) and vaginal delivery (p = .009) and with a higher percentage of vaginal delivery in less than 24 h in mothers with a very unfavourable cervix score (risk ratio (RR): 1.41, IC95% 1.17–1.69, p = .002). Successful inductions with misoprostol showed EHG parameter values significantly higher than basal state for amplitude and pseudo Montevideo units (PMU) 60’ after drug administration, while spectral parameters significantly increased after 150’. This response was not observed in failed inductions. In the successful dinoprostone group, the duration and number of contractions increased significantly after 120’, PMU did so after 180’, and no significant differences were found for spectral parameters, possibly due to the slower pharmacokinetics of this drug. Conclusion: Successful inductions of labour by misoprostol are associated with earlier effective contractions than in labours induced by dinoprostone.

Non-invasive electrohysterogram recording using flexible concentric ring electrode.

Non-invasive electrohysterogram (EHG) recording could provide valuable information about uterine dynamics. Bipolar EHG has usually been performed using monopolar disposable electrodes. Recently concentric ring electrodes have been used for EHG recordings so as to acquire more localized electrical activity which may be helpful for deducing uterine contraction efficiency. Nevertheless concentric ring electrodes have commonly been implemented in rigid substrates. Therefore they do not adapt to the body surface curvature which may cause discomfort for patients and a poor contact between electrode and skin. The aim of this paper is to examine the feasibility of picking up EHG signals (BC-EHG) using a new flexible tripolar concentric ring (TCR) electrode placed on the abdominal surface, and to compare it with the conventional bipolar recordings. For this purpose, a total of 7 recording sessions were carried out in 7 pregnant women. Each recording implied simultaneous acquisition of one bipolar EHG signal and of two bipolar concentric EHG (BC-EHG) signals using the flexible TCR electrode. Then a set of temporal and spectral parameters was computed from both bipolar EHG and BC-EHG bursts. Experimental results show no noticeable difference in duration and in dominant frequency in Fast Wave High frequency range. Nonetheless, the low frequency content (0.1-0.2 Hz) of BC-EHG records is smaller than that of bipolar record. These results suggest that the new flexible TCR electrode permits to pick up uterine electrical activity and may provide additional information for deducing uterine efficiency.

Tripolar Flexible Concentric Ring Electrode Printed with Inkjet Technology for ECG Recording

Laplacian potential on the body surface can be estimated by means of concentric ring electrodes. It has been proved that bioelectrical surface recordings performed with such concentric ring electrodes improve spatial resolution compared to unipolar or bipolar disc electrodes. However, concentric ring electrodes have commonly been implemented in rigid substrates. Therefore they do not adapt to the body surface curvature what provokes discomfort to the patient and a poor contact that affects the signal quality. The aim of this work was to develop a new active concentric ring electrode on a flexible substrate for obtaining high spatial resolution ECG recording. Specifically the active electrode is made up of a disposable tripolar concentric ring electrode printed onto polyester film using inkjet technology, and a reusable signal preconditioning circuit. Simultaneous laplacian ECG recordings with the developed electrode and reduced Lead-I ECG with conventional disc electrodes were conducted in 7 subjects. The results show that the flexible active sensor can be used for picking up laplacian ECG with a similar signal quality than standard Lead-I ECG. This sensor could be used for ECG monitoring with enhanced spatial resolution.

Combined method for fetal electrocardiogram extraction from noninvasive abdominal recordings

Abdominal electrocardiogram (AECG) recording is a non-invasive method to assess fetal well-being during both pregnancy and delivery. However, AECG recording is contaminated by a series of physiological interferences which make difficult the extraction of morphological and temporal parameters of fetal ECG from the raw signals. In this work, it is proposed a combined method to extract the fetal ECG from AECG recording by removing the interferences on a cascade structure using a priori information about the signals nature. In this work, a total of 54 multichannel AECG recordings taken from 21 to 40 weeks of gestation were enrolled. Experimental results show that the proposed method outperforms conventional independent component analysis, and provides fetal heart rate detection in 80% of the cases. In addition it also permits to obtain fetal ECG morphology from AECG recordings.

Classifier of intestinal contractile activity degree based on internal electroenterogram recording

The study of the intestinal interdigestive motor migratory complex (IMMC) is relevant in gastroenterology because most of the gastrointestinal pathologies are reflected in anomalies of the IMMC. The aim of this work is to develop an automatic classifier to discriminate among the different intestinal contractile activity degrees (quiescence, irregular, and maximum contractile activity) that compound the IMMC from the internal recordings of electroenterogram. Spectral and statistical parameters estimated from the internal electroenterogram have been used as features to the classifiers based on Linear Discriminant Analysis (LDA) and linear Support Vector Machines (SVM). The accuracy obtained by the SVM classifier is slightly higher than that of the LDA classifier. An accuracy of around 91% was obtained for the binary SVM classifier (quiescence vs maximum activity) and around 74% for the multiclass one. The use of additional features, and non-linear SVM classifiers could yield better classification accuracy values. Nevertheless, preliminary results suggest that SVM classifiers could be a very helpful tool for automatic classification of intestinal contractile activity degrees and for the identification of the IMMC which could be used for diagnosing anomalies in the intestinal motor function.

Enhancement of laplacian EEnG from humans by means of an EMD-based method

Non-invasive recordings of intestinal myoelectrical activity (Electroenterogram, EEnG) are affected by very-low-frequency (VLF) interferences, respiration, ECG and movement artifacts. In order to identify the intestinal pacemaker activity (slow wave), VLF interferences and respiration should be removed from abdominal surface recordings. In this paper a method based on empirical mode decomposition is proposed to identify and cancel such interferences and to enhance external recordings of human EEnG. The study was carried out on 10 recording sessions in which it was acquired 3 surface EEnG signals by means of active laplacian electrodes, together with respiratory and ECG signals. The application of the proposed method permits to increase the signal-to-interference ratio of EEnG signals from − 7.9±3.3 dB to 6.1±2.7 dB. In addition, the method helps to identify the intestinal pacemaker activity from surface EEnG recordings: the dominant frequency of processed signals is 8.6±1.7 cpm which fits the frequency of the intestinal slow wave in the jejunum, whereas the dominant frequency of original signals was 1.6±1.1 cpm which is associated to VLF interferences.

Quantification of combined method for interferences reduction in multichannel surface electroenterogram

Surface electroenterogram (EEnG) is a non-invasive method for monitoring the intestinal motility. However, surface EEnG signals are contaminated by strong physiological interferences. The main interferences which affect high-frequency components of surface EEnG are cardiac activity and movement artifacts. The aim of this work is to quantify the effectiveness of a combined method based on empirical mode decomposition and independent component analysis to remove these interferences from multichannel surface EEnG. In order to do so, several parameters were calculated from five recording sessions: Signal-to-ECG interference ratio (S/I) and variation of energy over 2 Hz (EF2). The results show that the S/I of processed signals was significantly higher than that of original signals, moreover the improvement of the S/I ratio is due to the attenuation of energy associated to interference. The proposed method also allows cancelling movement artifacts from surface EEnG, reducing considerably the non-physiological variation of EF2. Furthermore after the application of the combined method, correlation coefficient between EF2 of internal recording with EF2 of surface recording is greatly higher. Therefore, the proposed method could be helpful to reduce high-frequency interferences in EEnG recording and to provide more robust non-invasive intestinal motility indicators.