João Bernardes

Evaluation of interobserver agreement of cardiotocograms.

Objective: To evaluate interobserver agreement in visual analysis of each cardiotocographic event. Methods: Three experts independently divided 16 antepartum and 17 intrapartum cardiotocograms into baseline segments, accelerations and decelerations, according to the FIGO guidelines. Baseline segments were further classified as having normal, reduced or increased variability and decelerations as early, late and variable. Uterine activity was divided into tonus and contractions. Agreement was assessed by the proportions of agreement (pa) with 95% confidence intervals. Results: Reproducibility in assessment of baseline segments with normal variability, accelerations and uterine activity was acceptable (pa = 0.56–0.71) whereas that of other segments was not (pa = 0.14–0.45). Conclusions: Analysis of most cardiotocographic events is poorly reproducible, even when experts use the FIGO guidelines. This may be explained by some still ambiguous guidelines, by eyeball limitations in evaluation of subtle events, and by the incapacity of busy clinicians to assess complex and multiple cardiotocographic events in a systematic and disciplined fashion.

Inconsistencies in classification by experts of cardiotocograms and subsequent clinical decision

Inter‐observer agreement in the interpretation according to the FIGO guidelines of 33 cardiotocographic tracings by experts and subsequent clinical decision was evaluated, using the kappa statistic (K) and the proportions of agreement (Pa). Overall agreement in the classification of tracings was fair (K = 0.48) and was better for normal (Pa = 0.62), than for suspicious (Pa = 0.42) or pathologic tracings (Pa = 0.25). Overall agreement on clinical decision was slightly higher (K = 0.59), but mostly was centred on the decision to take ‘no action’ (Pa = 0.79). Experts especially disagreed over the decisions to ‘monitor closely’ (Pa = 0.14) or to ‘intervene immediately’ (Pa = 0.38). These limitations should be taken into account in clinical audits and in medical jurisprudence.

The Porto system for automated cardiotocographic signal analysis

Cardiotocography (CTG) lacks reliability and reproducibility and these problems are believed to be overcome by computer analysis. In this article we describe a system developed for routine clinical automated CTG analysis based on a low cost personal computer. Presently the system has processed 70 ten minute tracings. Fetal heart rate baseline, acceleration--deceleration detection, and long term variability estimation were performed in a satisfactory way.

Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery

Linear and nonlinear fetal heart rate (FHR) indices, namely mean FHR, interval index (II), very low, low and high frequencies, approximate (ApEn) and sample entropy (SampEn), were computed, immediately before delivery, in the initial and final FHR tracing segments, from 48 normal, 10 mildly acidemic and 10 moderate-to-severely acidemic fetuses. Progression of labor was associated with a significant increase in linear frequency domain indices whereas nonlinear indices were significantly decreased. Moderate-to-severe fetal acidemia was associated with a significant decrease in nonlinear indices. The best discrimination between moderate-to-severe acidemic fetuses and the remaining cases was obtained combining II and ApEn(2,0.15), with a specificity of 71% and a sensitivity of 80%. These findings support the hypothesis of increased autonomic nervous system activity in the final minutes of labor and of decreased central nervous system activity, both in the final minutes of labor and in moderate-to-severe acidemic fetuses.

The limits of agreement and the intraclass correlation coefficient may be inconsistent in the interpretation of agreement.

OBJECTIVE To compare the interpretation of agreement in the prediction of neonatal outcome variables, using the limits of agreement (LA) and the intraclass correlation coefficient (ICC). STUDY DESIGN AND SETTING Three obstetricians were asked to predict neonatal outcomes independently based on the evaluation of intrapartum cardiotocographic tracings. Interobserver agreement was assessed with the LA and the ICC, and the results obtained were interpreted by six clinicians and six statisticians on a scale that established agreement as very poor, poor, fair, good, or very good. RESULTS Interpretation of the LA results was less consensual than the ICC results, with proportions of agreement of 0.36 (95% confidence interval [CI]: 0.28-0.44) vs. 0.63 (95% CI: 0.54-0.73), respectively. LA results suggested a fair to good agreement among obstetricians, whereas interpretation of ICC results suggested a poor to fair agreement. LA results were more plausible with reality, suggesting that obstetricians predicted neonatal outcomes better than randomly generated values, whereas it was not always the case with the ICC. CONCLUSIONS LA and ICC can provide inconsistent results in agreement studies. Accordingly, in the absence of better strategies to assess agreement, both should be used for this purpose, but their results need to be interpreted with caution keeping their respective limitations in mind.

Prediction of neonatal acidemia by computer analysis of fetal heart rate and ST event signals

OBJECTIVE The objective of the study was to evaluate the accuracy of computer analysis of fetal heart rate (FHR) and ST event signals in prediction of neonatal acidemia. STUDY DESIGN One hundred forty-eight FHR tracings were evaluated to identify red alerts provided by the system, based on automated analysis of FHR and ST event signals, and compared with the occurrence of umbilical artery acidemia (pH < or =7.05). RESULTS The presence of red alerts obtained sensitivity of 1.00 (95% confidence interval [CI], 0.56-1.00), specificity of 0.94 (95% CI, 0.89-0.97), positive predictive value (PPV) of 0.47 (95% CI, 0.22-0.72), negative predictive value (NPV) of 1 (95% CI, 0.96-1.00), positive likelihood ratio (PLR) of 17.6 (95% CI, 9.0-34.5), and negative likelihood ratio (NLR) of 0. When limiting analysis to red alerts that did not include ST data, sensitivity was 0.57 (95% CI, 0.20-0.88), specificity was 0.97 (95% CI, 0.92-0.99), PPV was 0.50 (95% CI, 0.17-0.82), NPV was 0.98 (95% CI, 0.93-0.99), PLR was 20.14 (95% CI, 6.3-64.2), and NLR was 0.44 (95% CI, 0.19-1.04). CONCLUSION Computer analysis of FHR and ST event signals provide higher accuracy in predicting neonatal academia.

Mechanical properties of polypropylene mesh used in pelvic floor repair

The aim of this study was the comparison of the stiffness of different meshes under two types of mechanical tests. Five different mesh types were mechanically tested. The methods used consisted on uniaxial tension test (tensile stiffness) and tape ring tests, experimental continuous compression of the mesh loops (flexural stiffness). The most significant difference of tensile stiffness behaviour appears between Aris™ and TVTO™. From the analysis of the experimental data, we divided the flexural stiffness, in two main groups. The first group includes Auto Suture™ and Aris™ meshes. The two meshes seem to have a similar flexural behaviour. The second group includes TVTO™, Uretex™ and Avaulta™. The difference between these two groups is clearly evident comparing TVTO™ and Aris™. This study shows that there are significant differences on the mechanical properties between urogynecology meshes.

Omniview-SisPorto 3.5 - a central fetal monitoring station with online alerts based on computerized cardiotocogram+ST event analysis.

Visual analysis of cardiotocograms is poorly reproducible and is currently recognized as the main weakness of the STAN methodology. The Omniview-SisPorto 3.5 program is the most recent version of a central monitoring system that provides visual and sound alerts, based on computer analysis of cardiotocographic and ST event features. This paper describes the programs main characteristics and provides an overview of the systems online alerts. Omniview-SisPorto 3.5 is the first central monitoring system to incorporate computerized analysis of cardiotocographic and ST event features, providing health professionals with online alerts for minor and major changes in monitored signals. The system is currently undergoing extensive clinical evaluation.

Twenty-five years after the FIGO guidelines for the use of fetal monitoring: Time for a simplified approach?

Twenty‐five years after the FIGO Workshop that produced the “Guidelines for the use of fetal monitoring,” these remain the only broad international consensus effort in this field. Documents of a similar nature have been produced by national institutions, with subsequent updates of the initial concepts. The 3‐class classification system has now been adopted by all the major guidelines, and while there are numerous similar features, and indeed many ideas were inspired by the FIGO guidelines, many key aspects still lack consensus. Making guidelines simpler and more objective may be an important step to guarantee a wide application and assimilation of the recommendations, as well as an enhanced reproducibility and increased memory retention.

Internal versus external intrapartum foetal heart rate monitoring: the effect on linear and nonlinear parameters.

The effect of foetal heart rate (FHR) acquisition mode on linear and nonlinear parameters is still largely unknown. In 33 normal labouring women, FHR signals were acquired simultaneously by an external ultrasound sensor applied to the maternal abdomen and an internal scalp electrode, in the minutes preceding delivery. For each case, the initial and final 5, 10 and 20 min segments were analysed, considering FHR signals at a frequency of 4 Hz (the frequency at which they are transmitted by the majority of commercialized foetal monitors). Several time and frequency domain linear and nonlinear FHR indices were computed in these segments, namely mean FHR, very low frequency (VLF), low frequency (LF), high frequency (HF), approximate entropy (ApEn) and sample entropy (SampEn). Parametric confidence intervals, statistical tests and correlation coefficients were calculated in order to evaluate the effect of internal versus external FHR monitoring modes on the considered indices. The whole evaluation was repeated using FHR signals at a frequency of 2 Hz. Most time domain linear indices were similar with external and internal monitoring in the initial and final segments of the tracings. However, linear frequency domain indices were poorly correlated in the final segments and had significantly different mean values in the initial segments. Nonlinear indices were significantly different in both initial and final segments. The correlation between 4 and 2 Hz sampled parameters was high for both linear and nonlinear indices (most correlation coefficient values ranging between 0.95 and 1) but nonlinear index values were significantly higher at 2 Hz. In conclusion, the mode used to acquire FHR signals and the sampling rate employed can significantly affect most FHR indices.