José Alberola-Rubio

Comparison of non-invasive electrohysterographic recording techniques for monitoring uterine dynamics

Non-invasive recording of uterine myoelectric activity (electrohysterogram, EHG) could provide an alternative to monitoring uterine dynamics by systems based on tocodynamometers (TOCO). Laplacian recording of bioelectric signals has been shown to give better spatial resolution and less interference than mono- and bipolar surface recordings. The aim of this work was to study the signal quality obtained from monopolar, bipolar and Laplacian techniques in EHG recordings, as well as to assess their ability to detect uterine contractions. Twenty-two recording sessions were carried out on singleton pregnant women during the active phase of labour. In each session the following simultaneous recordings were obtained: internal uterine pressure (IUP), external tension of abdominal wall (TOCO) and EHG signals (5 monopolar and 4 bipolar recordings, 1 discrete approximation to the Laplacian of the potential and 2 estimates of the Laplacian from two active annular electrodes). The results obtained show that EHG is able to detect a higher number of uterine contractions than TOCO. Laplacian recordings give improved signal quality over monopolar and bipolar techniques, reduce maternal cardiac interference and improve the signal-to-noise ratio. The optimal position for recording EHG was found to be the uterine median axis and the lower centre-right umbilical zone.

Automatic Identification of Motion Artifacts in EHG Recording for Robust Analysis of Uterine Contractions

Electrohysterography (EHG) is a noninvasive technique for monitoring uterine electrical activity. However, the presence of artifacts in the EHG signal may give rise to erroneous interpretations and make it difficult to extract useful information from these recordings. The aim of this work was to develop an automatic system of segmenting EHG recordings that distinguishes between uterine contractions and artifacts. Firstly, the segmentation is performed using an algorithm that generates the TOCO-like signal derived from the EHG and detects windows with significant changes in amplitude. After that, these segments are classified in two groups: artifacted and nonartifacted signals. To develop a classifier, a total of eleven spectral, temporal, and nonlinear features were calculated from EHG signal windows from 12 women in the first stage of labor that had previously been classified by experts. The combination of characteristics that led to the highest degree of accuracy in detecting artifacts was then determined. The results showed that it is possible to obtain automatic detection of motion artifacts in segmented EHG recordings with a precision of 92.2% using only seven features. The proposed algorithm and classifier together compose a useful tool for analyzing EHG signals and would help to promote clinical applications of this technique.

Neonatal Acid-Base Status in Term Fetuses: Mathematical Models Investigating Cerebroplacental Ratio and Birth Weight.

Objective: Cerebroplacental ratio (CPR) is emerging as a marker of fetal hypoxia at term. The aim of this study was to demonstrate graphically the interrelationships among CPR, birthweight (BW), and neonatal pH, and construct 2D and 3D representations of the areas with potential low pH. Methods: This was a retrospective study of 2,927 term fetuses evaluated according to BW and CPR. The outcome was the acid-base status at birth. Multivariate relationships among CPR, BW, and arterial and venous pH were depicted in 3D scattergrams. Subsequently, trend surfaces were calculated and represented in 2D contour graphs. Finally, 3D representations were constructed by smothering pH data using moving average filters. Results: The trend surfaces and the 2D and 3D contour graphs showed the complex association among the three variables. Although pH changed with CPR and BW, the influence of the BW was smaller than the influence of the CPR, with this effect being more evident in the venous than in the arterial pH. Conclusions: Two scenarios threaten fetal well-being at term: a very low birth weight and a very low fetal CPR. Our findings suggest that the importance of fetal hemodynamics in determining the acid-base status at birth surpasses that of fetal weight.

Prediction of labor using non-invasive laplacian EHG recordings

Non-invasive electrohysterogram (EHG) recordings could be used as an alternative technique for monitoring uterine dynamics. Bipolar recordings of EHG have proven to provide valuable information to predict labor. Recently it has been stated that uterine EHG bursts could also be identified in Laplacian recordings on abdominal surface. Taking into account that Laplacian potential technique permits to acquire more localized electrical activity than conventional recordings; these recordings could also be helpful for deducing uterine contraction efficiency. The aim of this paper is to examine the feasibility of Laplacian potential EHG recording for labor prediction and to compare it with monopolar recordings. To this purpose, a total of 42 EHG recordings were acquired from women of similar gestational age: 29 antepartum patients, and 13 patients in labor. Then linear and non-linear classifiers have been implemented using EHG burst parameters as input features. Experimental results show significant differences in temporal and spectral parameters in both monopolar and Laplacian potential recordings between the two groups. In addition, support vector machine based classifier achieved an accuracy of 93% for labor prediction for monopolar recordings, 92% for bipolar recordings and 91% for Laplacian potential.

Recording of electrohysterogram laplacian potential

Preterm birth is the main cause of the neonatal morbidity. Noninvasive recording of uterine myoelectrical activity (electrohysterogram, EHG) could be an alternative to the monitoring of uterine dynamics which are currently based on tocodynamometers (TOCO). The analysis of uterine electromyogram characteristics could help the early diagnosis of preterm birth. Laplacian recordings of other bioelectrical signals have proved to enhance spatial selectivity and to reduce interferences in comparison to monopolar and bipolar surface recordings. The main objective of this paper is to check the feasibility of the noninvasive recording of uterine myoelectrical activity by means of laplacian techniques. Four bipolar EHG signals, discrete laplacian obtained from five monopolar electrodes and the signals picked up by two active concentric-ringed-electrodes were recorded on 5 women with spontaneous or induced labor. Intrauterine pressure (IUP) and TOCO were also simultaneously recorded. To evaluate the uterine contraction detectability of the different noninvasive methods in comparison to IUP the contractions consistency index (CCI) was calculated. Results show that TOCO is less consistent (83%) than most EHG bipolar recording channels (91%, 83%, 87%, and 76%) to detect the uterine contractions identified in IUP. Moreover laplacian EHG signals picked up by ringed-electrodes proved to be as consistent (91%) as the best bipolar recordings in addition to significantly reduce ECG interference.

Progression of Doppler changes in early-onset small for gestational age fetuses. How frequent are the different progression sequences?

Abstract Objective: To evaluate the progression of Doppler abnormalities in early-onset fetal smallness (SGA). Methods: A total of 948 Doppler examinations of the umbilical artery (UA), middle cerebral artery (MCA) and ductus venosus (DV), belonging to 405 early-onset SGA fetuses, were studied, evaluating the sequences of Doppler progression, the interval examination-labor at which Doppler became abnormal and the cumulative sum of Doppler anomalies in relation with labor proximity. Results: The most frequent sequences were that in which only the UA pulsatility index (PI) became abnormal (42.1%) and that in which an abnormal UA PI appeared first, followed by an abnormal MCA PI (24.2%). In general, 71.3% of the fetuses followed the classical progression sequence UA→MCA→DV, mostly in the early stages of growth restriction (84.1%). In addition, the UA PI was the first parameter to be affected (9 weeks before delivery), followed by the MCA PI and the DV PIV (1 and 0 weeks). Finally, the UA PI began to sum anomalies 5 weeks before delivery, while the MCA and DV did it at 3 and 1 weeks before the pregnancy ended. Conclusions: In early-onset SGA fetuses, Doppler progression tends to follow a predictable order, with sequential changes in the umbilical, cerebral and DV impedances.

Electrohysterography in the diagnosis of preterm birth: a review

Preterm birth (PTB) is one of the most common and serious complications in pregnancy. About 15 million preterm neonates are born every year, with ratios of 10-15% of total births. In industrialized countries, preterm delivery is responsible for 70% of mortality and 75% of morbidity in the neonatal period. Diagnostic means for its timely risk assessment are lacking and the underlying physiological mechanisms are unclear. Surface recording of the uterine myoelectrical activity (electrohysterogram, EHG) has emerged as a better uterine dynamics monitoring technique than traditional surface pressure recordings and provides information on the condition of uterine muscle in different obstetrical scenarios with emphasis on predicting preterm deliveries. OBJECTIVE A comprehensive review of the literature was performed on studies related to the use of the electrohysterogram in the PTB context. APPROACH This review presents and discusses the results according to the different types of parameter (temporal and spectral, non-linear and bivariate) used for EHG characterization. MAIN RESULTS Electrohysterogram analysis reveals that the uterine electrophysiological changes that precede spontaneous preterm labor are associated with contractions of more intensity, higher frequency content, faster and more organized propagated activity and stronger coupling of different uterine areas. Temporal, spectral, non-linear and bivariate EHG analyses therefore provide useful and complementary information. Classificatory techniques of different types and varying complexity have been developed to diagnose PTB. The information derived from these different types of EHG parameters, either individually or in combination, is able to provide more accurate predictions of PTB than current clinical methods. However, in order to extend EHG to clinical applications, the recording set-up should be simplified, be less intrusive and more robust-and signal analysis should be automated without requiring much supervision and yield physiologically interpretable results. SIGNIFICANCE This review provides a general background to PTB and describes how EHG can be used to better understand its underlying physiological mechanisms and improve its prediction. The findings will help future research workers to decide the most appropriate EHG features to be used in their analyses and facilitate future clinical EHG applications in order to improve PTB prediction.

Fetal cerebral and umbilical Doppler in pregnancies complicated by late-onset placental abruption.

Abstract Objective: To evaluate whether changes in the cerebroplacental Doppler and birth weight (BW) suggestive of chronic fetal hypoxemia, precede the development of late-onset placental abruption (PA) after 32 weeks. Methods: In a multicenter retrospective study, the Doppler examinations of the fetal umbilical artery (UA) and middle cerebral artery (MCA) recorded after 32 weeks were collected in pregnancies subsequently developing PA. The BW centiles were calculated and the MCA pulsatility indices (PI), and UA PI were converted into multiples of the median (MoM). Afterwards, a comparison was made with a group of fetuses, which did not develop PA. Logistic regression was used to adjust for potential confounders and evaluate the feasibility of the prediction model. Results: Pregnancies complicated by late-onset PA (n = 31) presented lower MCA PI (p = 0.015) and were smaller (p < 0.001) than those who did not (n = 1294). Logistic regression analysis indicated that cerebral vasodilation was more important than umbilical flow in the explanation of PA (MCA PI OR = 0.106, p = 0.014 and UA PI OR 1.901, p = 0.32). In addition, the influence of BW exerted was residual (BW centile OR = 0.989, p = 0.15). Conclusions: Fetuses developing late-onset PA demonstrate significant cerebral vasodilation with scarce placental dysfunction, suggesting the existence of some kind of chronic hypoxemia that follows the late-onset pattern.

Prediction of labor onset type

BACKGROUND AND OBJECTIVE Induction of labor (IOL) is a medical procedure used to initiate uterine contractions to achieve delivery. IOL entails medical risks and has a significant impact on both the mothers and newborns well-being. The assistance provided by an automatic system to help distinguish patients that will achieve labor spontaneously from those that will need late-term IOL would help clinicians and mothers to take an informed decision about prolonging pregnancy. With this aim, we developed and evaluated predictive models using not only traditional obstetrical data but also electrophysiological parameters derived from the electrohysterogram (EHG). METHODS EHG recordings were made on singleton term pregnancies. A set of 10 temporal and spectral parameters was calculated to characterize EHG bursts and a further set of 6 common obstetrical parameters was also considered in the predictive models design. Different models were implemented based on single layer Support Vector Machines (SVM) and with aggregation of majority voting of SVM (double layer), to distinguish between the two groups: term spontaneous labor (≤41 weeks of gestation) and IOL late-term labor. The areas under the curve (AUC) of the models were compared. RESULTS The obstetrical and EHG parameters of the two groups did not show statistically significant differences. The best results of non-contextualized single input parameter SVM models were achieved by the Bishop Score (AUC= 0.65) and GA at recording time (AUC= 0.68) obstetrical parameters. The EHG parameter median frequency, when contextualized with the two obstetrical parameters improved these results, reaching AUC= 0.76. Multiple input SVM obtained AUC= 0.70 for all EHG parameters. Aggregation of majority voting of SVM models using contextualized EHG parameters achieved the best result AUC= 0.93. CONCLUSIONS Measuring the electrophysiological uterine condition by means of electrohysterographic recordings yielded a promising clinical decision support system for distinguishing patients that will spontaneously achieve active labor before the end of full term from those who will require late term IOL. The importance of considering these EHG measurements in the patients individual context was also shown by combining EHG parameters with obstetrical parameters. Clinicians considering elective labor induction would benefit from this technique.

Feasibility of Labor Induction Success Prediction based on Uterine Myoelectric Activity Spectral Analysis

Labor induction using prostaglandins (PG) is a common practice to promote uterine contractions and to facilitate cervical ripening. However, not all cases of labor inductions result in vaginal deliveries and it has been associated with an increased risk of cesarean delivery. This last situation is associated to a greater healthcare economic impact and to an increment in the maternal and fetal mortality and morbidity. Obstetricians face different scenarios daily during a labor induction and it would be advantageous to be able to infer the result of the labor induction for a better labor management. Uterine electrohysterogram (EHG) has been proven to play an outstanding role in monitoring uterine dynamics and in characterizing the uterine myoelectrical activity. Therefore, the aim of this study was to characterize and to compare the response of uterine myoelectrical activity to labor induction drugs for different labor induction outcomes by obtaining and analyzing the evolution of spectral parameters from EHG records picked up during the first 4 hours after labor induction onset. Specifically, deciles from the EHG-bursts’ power spectral density (PSD) were worked out. Our results showed that deciles D8 and D9 are able to discriminate between women who achieved active phase of labor and those who did not. For women who achieved active phase of labor, D5 makes it possible to separate women who delivered vaginally and those who underwent a cesarean section; finally D2-D6 enabled us to distinguish vaginal deliveries within 24 hours after induction onset from the other outcomes. Thus, deciles computed from EHG PSD are potentially useful to discriminate the different outcomes of a labor induction, suggesting the feasibility of induction success prediction based on EHG recording.