Dorothee Marossero

Monitoring Contractions in Obese Parturients : Electrohysterography Compared With Traditional Monitoring

OBJECTIVE: To compare electrohysterogram-derived contractions with both tocodynamometry and intrauterine pressure monitoring in obese laboring women. METHODS: From a large database of laboring patients with electrohysterogram monitoring, obese subjects were selected in whom data were recorded for at least 30 minutes before and after intrauterine pressure catheter placement for obstetric indication. Using a contraction detection algorithm, the relationship between the methods was determined with regard to both frequency and contraction duration. RESULTS: Of the 25 subjects (median body mass index 39.6 [25th percentile 36.5, 75th percentile 46.3]), seven underwent amniotomy at the time of intrauterine pressure catheter placement. Tocodynamometry identified 248 contractions compared with 336 by electrohysterography, whereas intrauterine pressure catheter monitoring identified 319 contractions compared with 342 by electrohysterography. Using the Contractions Consistency Index, electrohysterogram contraction detection correlated better with the intrauterine pressure catheter (0.94±0.06) than with tocodynamometry (0.77±0.25), P=.004. Electrohysterogram-derived contraction lengths closely approximated those calculated from the intrauterine pressure catheter signal. CONCLUSION: Contraction monitoring routinely is employed for managing labor, and tocodynamometry may be unreliable in obese parturients. In the obese women in this study, the electrohysterogram-derived contraction pattern correlated better with the intrauterine pressure catheter than tocodynamometry. Electrohysterography may provide another noninvasive means of monitoring labor, particularly for those women in whom tocodynamometry is inadequate. LEVEL OF EVIDENCE: II

Spatiotemporal electrohysterography patterns in normal and arrested labor

OBJECTIVE The purpose of this study was to investigate the spatiotemporal patterns of uterine electrical activity in normal and arrested labors. STUDY DESIGN From a database of electrohysterograms, 12 subjects who underwent cesarean delivery for active-phase arrest were each matched with 2 vaginally delivered controls. Using 30-minute segments of the electrohysterogram during the arrest, or the same dilation in controls, the center of uterine electrical activity was derived. The vertical motion of this center of uterine activity was determined for each contraction and the frequencies of movement patterns analyzed. RESULTS Predominantly upward movement of the center of uterine activity (longer and/or stronger contraction at the fundus) was more common with normal dilation (P = .003). Receiver operating characteristic curve analysis gave an area under the curve of 0.91 for predicting outcome (vaginal vs cesarean delivery). CONCLUSION There is a significant correlation between upward movement of the center of uterine activity (fundal dominance) and current labor progress.

Independent components analysis for fetal electrocardiogram extraction: a case for the data efficient Mermaid algorithm

Fetal heart rate (FHR) monitoring is currently the primary methodology for antenatal determination of fetal well-being. Currently, the FHR can be detected with ultrasonography, but the additional information from fetal electrocardiogram (FECG) is only available via an invasive scalp electrode. A cost effective noninvasive monitoring through standard ECG electrodes could be used on nearly every patient in lieu of the ultrasound monitors. In this method, a number of electrodes are positioned on the abdomen of the mother to collect, simultaneously, various combinations of the signals including the heartbeats of the mother and the fetus. For accurate fetal heart-rate estimation, a clean FECG must be extracted from the collected mixtures. It is well known that this can be achieved using blind source separation (BSS) techniques. In this paper, the performance of the Mermaid algorithm, which is based on minimizing Renyis mutual information, is evaluated on this problem of great practical importance. The effectiveness and data efficiency of Mermaid and its superiority over alternative information theoretic BSS algorithms are illustrated using artificially mixed ECG signals as well as fetal heart rate estimates in real ECG mixtures.

Prediction of Intrauterine Pressure From Electrohysterography Using Optimal Linear Filtering

We propose a method of predicting intrauterine pressure (IUP) from external electrohysterograms (EHG) using a causal FIR Wiener filter. IUP and 8-channel EHG data were collected simultaneously from 14 laboring patients at term, and prediction models were trained and tested using 10-min windows for each patient and channel. RMS prediction error varied between 5-14 mmHg across all patients. We performed a 4-way analysis of variance on the RMS error, which varied across patients, channels, time (test window) and model (train window). The patient-channel interaction was the most significant factor while channel alone was not significant, indicating that different channels produced significantly different RMS errors depending on the patient. The channel-time factor was significant due to single-channel bursty noise, while time was a significant factor due to multichannel bursty noise. The time-model interaction was not significant, supporting the assumption that the random process generating the IUP and EHG signals was stationary. The results demonstrate the capabilities of optimal linear filter in predicting IUP from external EHG and offer insight into the factors that affect prediction error of IUP from multichannel EHG recordings

Prediction of intrauterine pressure waveform from transabdominal electrohysterography

Objective. We investigated the ability to non-invasively obtain uterine electromyograms (EMG; electrohysterogram (EHG)) to predict the intrauterine pressure (IUP) waveform. Study design. Patients enrolled in a term labor study of trans-abdominal electrical activity, who underwent IUP monitoring for obstetric indication, were included in this study (n = 14). EHG signals were processed and prediction filters trained against the IUP from the same patient. Sixty-eight 10-minute traces each of EHG and IUP waveforms were reviewed (Montevideo unit (MVU) calculation) by two experienced labor nurses and one obstetrician, blinded to patient and EHG vs. IUP output. In addition, area under the contraction curve (AUC), contraction detection and duration were compared. Results. EHG-derived MVUs statistically correlated with IUP (r = 0.795; p < 0.0001), but mathematically differed by 17±20% with 83% of EHG MVUs underestimating the IUP. The coefficients of variation between the two methods were relatively high (∼20%), and these could not be substantially corrected via calibration. AUC differed by 8±19% with 69% of EHG-derived AUC underestimating the IUP. EHG detected 98% of 362 IUP contractions, with 8% over-detection. Contraction duration was similar: 56.4±11.9 s vs. 55.7±13.0 s, for IUP and EHG, respectively. Conclusion. EHG-based contraction monitoring approximates IUP monitoring for contraction detection and duration. The correlation with contraction height (MVU) and AUC is much weaker with the investigated signal-processing algorithm.