Development of a stand-alone device to simultaneously record cardiotocography biosignals in an open format for testing methods of assessing fetal heart rate variability

• DOI: https://doi.org/10.22533/at.ed.317472426026

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• Abstract: Fetal hypoxia/acidemia recognition improves with computerized analysis of biosignals collected from cardiotocography (CTG), particularly the assesment of short-term variability (STV) of fetal heart rate (FHR). Several methods to compute STV have been described with varied performance results according to acquisition method, sampling and storage rates and algorithm definition. Dawes-Redman algorithm (STV16) is the most widely reproduced in available commercial systems. However, it shows a low correlation with the beat-to-beat variation determined from fetal electrocardiographic signal (fECG). STV240 algorithm has been introduced in an attempt to approximate STV assessment to real beat-to-beat variation. There is no comparison in the literature between these two algorithms, taking as gold standard variability obtained from ECG tracing. With a view to providing reliable records for the standardization and comparison of STV algorithms, most notably, STV16 and STV240, we have designed, assembled and developed a stand-alone device well able to connect with different CTG machines and collect simultaneously biomedical signals of interest, particularly FHR, uterine activity and fECG, from the standard monitor outputs. It generates a file in an open format that allows assessment of computerized parameters of CTG. By means of R-R instantaneous variation from fECG as a reference we have found no agreement by Intraclass Correlation Coefficient between STV16 and STV240, neither with STV calculated from fECG. Nevertheless, the last two correlated closely. Standardisation of algorithms, interoperability and research in computerized CTG need to be provided with simultaneous recordings of biosignals involved, including the ECG raw signal. STV16 and STV240 require individualised normal ranges.