Comparison of the effect of different sampling modes on computer analysis of cardiotocograms Hernâni Gonçalves a,n , Joana Chaves b , Antónia Costa b,c,d , Diogo Ayres-de-Campos b,c,d , João Bernardes a,b,c,e a Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr Plácido da Costa, 4200-450 Porto, Portugal b Department of Obstetrics and Gynecology, Medical School, University of Porto, Portugal c Department of Obstetrics and Gynecology, São João Hospital, Portugal d INEB –Institute of Biomedical Engineering, Porto; I3S – Institute for Research and Innovation in Health, University of Porto, Portugal e Hospital Pedro Hispano, Unidade Local de Saúde de Matosinhos, Portugal article info Article history: Received 27 February 2015 Accepted 15 June 2015 Keywords: Fetal heart rate Fetal monitoring Cardiotocography Signal processing Computer analysis Electrocardiography abstract Background: Cardiotocographic (CTG) monitors may provide fetal heart rate (FHR) signals as beat-to-beat (BTB) or alternatively at a fixed sampling rate. The aim of this study was to assess the effect of different sampling modes on the evaluation provided by a commercially available system for computer analysis of CTGs. Methods: Internal FHR signals were acquired during the last hour of labor in 27 singleton term cephalic pregnancies, using the STAN S31 s fetal monitor (Neoventa, Gothemburg, Sweden). BTB and 4 Hz sampling outputs of the monitor were compared using the Omniview-SisPorto s system for computer analysis of CTGs (Speculum, Lisbon, Portugal). The following parameters were analyzed: signal loss, signal quality, baseline, accelerations, decelerations, percentage of abnormal short-term variability (%aSTV), abnormal long-term variability (%aLTV), average short-term variability (avSTV) and the system's clinical alerts. Statistical inference was performed using the Spearman correlation coefficient, 95% nonparametric confidence intervals, Wilcoxon and McNemar statistical tests, setting significance at 0.05, and a non-parametric measure of disagreement (valued 0–1 from lowest to highest disagreement). Results: Comparing BTB with 4 Hz sampling, the median values for signal quality (95% versus 96%), number of accelerations (5 versus 7) and %aSTV (31 versus 39) were significantly lower in the former. On the other hand, with BTB signals the median value of avSTV was significantly higher (3.1 versus 2.3). Nevertheless, BTB and 4 Hz parameters were highly correlated (r ¼0.89–0.97), and there were no significant differences in the quantification of the number of decelerations or in the clinical alerts elicited by the system. Conclusions: In conclusion, different sampling modes have a significant effect on the parameters provided by computer analysis of CTGs that are related with the quantification of STV, with a small impact on baseline estimation and on the subsequent quantification of accelerations. However, there does not seem to be significant impact on the quantification of decelerations or on the alerts provided by the system. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction Cardiotocography (CTG) consists on the simultaneous recording of fetal heart rate (FHR) and uterine contraction (UC) signals, and is widely used in industrialized countries to monitor the fetal oxygenation during labor. A small number of computer systems for analysis of the CTG have been developed in order to overcome the limitations of visual assessment of tracings by healthcare professionals, and to improve the objectivity and reproducibility of CTG interpretation [14]. These systems comprise the computation of CTG parameters, such as baseline, variability, accelerations and decelerations, which have been shown to be related with the state of fetal oxygenation and with the activity of the autonomic nervous system [4]. Commercially available CTG monitors acquire beat-to-beat (BTB) intervals measured in milliseconds from fetal Doppler or Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/cbm Computers in Biology and Medicine http://dx.doi.org/10.1016/j.compbiomed.2015.06.011 0010-4825/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ351 225513622. E-mail addresses: hernanigoncalves@med.up.pt (H. Gonçalves), joanaaraujochaves@gmail.com (J. Chaves), cosantonia@gmail.com (A. Costa), dcampos@med.up.pt (D. Ayres-de-Campos), jbernardes59@gmail.com (J. Bernardes). Computers in Biology and Medicine 64 (2015) 62–66