Estimation of internal uterine pressure by joint amplitude and frequency analysis of electrohysterographic signals

Abstract

Monitoring the uterine contraction provides important prognostic information during pregnancy and parturition. The existing methods employed in clinical practice impose a compromise between reliability and invasiveness. A promising technique for uterine contraction monitoring is electrohysterography (EHG). The EHG signal measures the electrical activity which triggers the contraction of the uterine muscle. In this paper, a non-invasive method for intrauterine pressure (IUP) estimation by EHG signal analysis is proposed. The EHG signal is regarded as a non-stationary signal whose frequency and amplitude characteristics are related to the IUP. After acquisition in a multi-channel configuration, the EHG signal is therefore analyzed in the time-frequency domain. A first estimation of the IUP is then derived by calculation of the unnormalized first statistical moment of the frequency spectrum. The estimation accuracy is finally increased by identification of a second-order polynomial model. The proposed method is compared to root mean squared analysis and optimal linear filtering and validated by simultaneous measurement of the IUP on nine women during labor. The results suggest that the proposed EHG signal analysis provides an accurate estimate of the IUP.

Modeling and Identification of the Electrohysterographic Volume Conductor by High-Density Electrodes

“…By analyzing a set of previous measurement performed with electrodes distributed on the abdomen, the signals recorded by electrodes placed in this region resulted less affected by movement artifacts, such as respiration, than the signals recorded by electrodes placed in other locations [31]. The common reference for the monopolar EHG signals recorded by the HD electrode was placed on the right hip, close to the ground (GRD) electrode.…”

Combining data fusion with multiresolution analysis for improving the classification accuracy of uterine EMG signals

“…The results revealed first that the classification performance varied from one channel to another. One possible explanation of this observable fact is that the characteristics of the uterine electrical activity are influenced by the position of the recording electrode: on the one hand, the distance between the recording position on the skin and the signal source in the myometrium is reduced at the median axis with respect to other electrodes [3,39,40]. There are more visceral tissues between the skin and the uterus at the extremities than on the middle of the median axis of woman's abdomen [40].…”

“…The real uterine EMG signals used in this study were recorded on 32 women: 22 women were recorded during pregnancy (33 -41 week of gestation, WG), 7 during labor (37 -42 WG) and 3 during both pregnancy and labor (33)(34)(35)(36)(37)(38)(39)(40)(41)(42). The mean and standard deviations of the gestational ages for pregnancy and labor were 34.14 ± 3.94 and 39.6 ± 1.75 weeks, respectively.…”

Electrohysterographic conduction velocity estimation

“…Several techniques have been proposed for the analysis of the EHG. Some authors have proposed reliable techniques for the noninvasive estimation of the intrauterine pressure [2], while other authors could distinguish between two different EHG frequency components [3], possibly being able to predict the course of pregnancy. The ultimate goal and main challenge remains the prediction of preterm delivery.…”

“…Given the EHG frequency content, usually lower than 1 Hz [2], this characteristic is 978-1-4244-3296-7/09/$25.00 ©2009 IEEE highly desirable, permitting low sampling rates and, therefore, reducing the complexity of the acquisition/analysis system. The ML approach [6], compared to the phase difference method, permits a complete exploitation of our multichannel measurements because it uses all the available acquisition channels, leading to an increased robustness to a low signalto-noise ratio (SNR).…”