title: Comparison of the effect of different sampling modes on computer analysis of cardiotocograms.
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(®) fetal monitor (Neoventa, Gothemburg, Sweden). BTB and 4 Hz sampling outputs of the monitor were compared using the Omniview-SisPorto(®) 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=0.89-0.97), 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.
authors.affiliation: Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr Plácido da Costa, 4200-450 Porto, Portugal. Electronic address: hernanigoncalves@med.up.pt.
authors.forename: Hernâni
authors.initials: H
authors.lastname: Gonçalves
authors.affiliation: Department of Obstetrics and Gynecology, Medical School, University of Porto, Portugal. Electronic address: joanaaraujochaves@gmail.com.
authors.forename: Joana
authors.initials: J
authors.lastname: Chaves
authors.affiliation: Department of Obstetrics and Gynecology, Medical School, University of Porto, Portugal; Department of Obstetrics and Gynecology, São João Hospital, Portugal; INEB -Institute of Biomedical Engineering, Porto; I3S - Institute for Research and Innovation in Health, University of Porto, Portugal. Electronic address: cosantonia@gmail.com.
authors.forename: Antónia
authors.initials: A
authors.lastname: Costa
authors.affiliation: Department of Obstetrics and Gynecology, Medical School, University of Porto, Portugal; Department of Obstetrics and Gynecology, São João Hospital, Portugal; INEB -Institute of Biomedical Engineering, Porto; I3S - Institute for Research and Innovation in Health, University of Porto, Portugal. Electronic address: dcampos@med.up.pt.
authors.forename: Diogo
authors.initials: D
authors.lastname: Ayres-de-Campos
authors.affiliation: Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr Plácido da Costa, 4200-450 Porto, Portugal; Department of Obstetrics and Gynecology, Medical School, University of Porto, Portugal; Department of Obstetrics and Gynecology, São João Hospital, Portugal; Hospital Pedro Hispano, Unidade Local de Saúde de Matosinhos, Portugal. Electronic address: jbernardes59@gmail.com.
authors.forename: João
authors.initials: J
authors.lastname: Bernardes
mesh_terms: D015148:Cardiotocography / Q000379:methods*; D004562:Electrocardiography; D006340:Heart Rate, Fetal / Q000502:physiology; D006801:Humans; D012815:Signal Processing, Computer-Assisted
keywords: Cardiotocography; Computer analysis; Electrocardiography; Fetal heart rate; Fetal monitoring; Signal processing