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Coping with limitations of fetal monitoring instrumentation to improve heart rhythm variability assessment

Kupka Tomasz, Matonia Adam, Jezewski Michal, Horoba Krzysztof, Wrobel Janusz, Jezewski Janusz

Biocybernetics and Biomedical Engineering

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2020

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Vol. 40, no. 1

388--403

EN

The most commonly used method of fetal monitoring is based on analysis of the fetal heart activity. Computer-aided fetal monitoring enables extraction of information hidden for visual interpretation – the instantaneous fetal heart rate (FHR) variability. The most natural method of obtaining FHR signal is fetal electrocardiography (FECG), where the FHR has a natural form of unevenly spaced time series of events – heart beats detected in FECG. However, because of problems with FECG recording, the today's instrumentation is based on monitoring of mechanical activity of the fetal heart by means of Doppler ultrasound technique. The ultrasound signal periodicity is determined with autocorrelation methods, so the FHR output signal has a form of evenly spaced instantaneous measurements, some of which are incorrect or duplicate. The aim of the work was to develop a correction algorithm for recognition and removal of these invalid values, to reproduce the FHR signal as time series of events. The new algorithm was compared to other known methods basing on the collected research material and defined performance measures. Thanks to the reference FECG signal registered simultaneously, a detailed analysis of algorithms performance at the level of true heart cycles was possible. Additionally, the influence of signal correction on indices describing the instantaneous FHR variability was evaluated. The obtained results showed that although changing the FHR signal form into time series of events improved the accuracy of indices, but in relation to beat-to-beat variability, that accuracy still does not ensure reliable analysis of instantaneous FHR variability.

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The influence of signal loss episodes on fetal heart rate variability measures

Wróbel J., Roj D., Jeżewski J., Horoba K., Kupka T., Jeżewski M.

Journal of Medical Informatics & Technologies

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2014

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Vol. 23

35--42

EN

The most important features indicating appropriate fetal development are the measures of instantaneous variability of a fetal heart rate (FHR), describing fluctuations of the beat-to-beat heart intervals. The most popular method for the FHR acquisition is the Doppler ultrasound technique. However, it is very sensitive to various motion artifacts distorting the signal being acquired. The aim of our work was to evaluate the influence of signal loss episodes on the parameters quantitatively describing the instantaneous variability of the FHR. For this purpose we artificially inserted signal loss episodes to the recordings, in different patterns and percentage, in accordance with the real characteristics of the signal loss segments. We particularly would like to answer the question if the signals with significant amount of signal loss can be reliably evaluated by means of instantaneous variability measures, and which of these measures (numerical indices) are more robust to the missing values.

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Reconstruction of FHR series recorded via ultrasound - method validation using abdominal fetal electrocardiography

Kupka T., Horoba K., Roj D., Matonia A., Czabanski R., Jezewski M.

Journal of Medical Informatics & Technologies

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2013

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Vol. 22

135--141

EN

Analysis of variability of the fetal heart rate (FHR) is very important for fetal wellbeing assessment. The beat-to-beat variability is described quantitatively by the indices originated from invasive fetal electrocardiography which provides the FHR signal in a form of time event series. Nowadays, monitoring instrumentation is based on Doppler ultrasound technology. The fetal monitors provide the output signal in a form of evenly spaced measurements. The goal of this work is to present a new method for the FHR signal processing, which enables extraction of time series of consecutive heartbeat intervals from the evenly repeated values. The proposed correction algorithm enables recognition and removal of the duplicated measurements. Reliable evaluation of the algorithm requires the reference event series, thus the FHR signals were obtained from abdominal fetal electrocardiograms to be used in this research study.

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Reliability and quality of ultrasound measurements of fetal heart rate variability

Jeżewski J., Wróbel J., Kupka T., Matonia A., Horoba K., Widera M.

Journal of Medical Informatics & Technologies

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2003

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Vol. 6

IT21--26

EN

This work was aimed at assessment of usability of Doppler ultrasound method for the analysis of fetal heart rate variability at a level of single heart beats. The purpose of this study was to check if today fetal monitors provide the signal of accuracy comparable with an electrocardiography method. The virtual instrumentation software for measurement system and processing of acquired signals was implemented using LABVIEW environment. The results obtained reveal that accuracy of today monitors which use Doppler ultrasound technique is sufficient for visual analysis of the FHR traces. However, for the computerized analysis at a beat-to-beat level, this accuracy is below the acceptable value.