In Practice: Maternal Heart Rate Artifact.

Objective Our previous work examined the effect on assessment of fetal well-being when presenting twin fetal heart rate tracings (FHRT) simultaneously on screen. To further examine the potential impact of subconscious perceptual influences on fetal well-being, the current study presented singleton FHRT with and without simultaneous presentation of maternal heart rate in a within-subjects design. Tracings were taken from archival cases with either normal or abnormal Apgar scores to identify differential impact depending on final outcome. All tracings were evaluated for variability, accelerations, decelerations, and overall concern. Study design Obstetrical medical professionals (nurses, physician assistants, and physicians; N = 32) assessed FHRTs from 20 singleton gestations that resulted in live births (half with normal Apgar scores (control group), half with a 5-minute Apgar < 7 (at-risk group)) presented either alone or with maternal heart rate on the same tracing. Nurses were naïve to the fact that the fetal heart rate tracings presented in the unpaired condition were the same as those presented in the paired condition. Within-subjects assessments were then compared between the two conditions. Results Each nurse participant completed ratings on four metrics for each of 20 singleton gestations across two conditions, plus rated three tracings per condition again to determine test-retest reliability within each condition (52 FHRT assessments, 208 metrics total per participant). The intraobserver impact of visual context was calculated as the frequency of changed opinions regarding an individual metric (e.g. variability) between the paired and unpaired contexts for control versus at-risk FHRT. Participants demonstrated substantial self-agreement when assessing variability, accelerations, and decelerations for control FHRT, but only moderate agreement for the same metrics when assessing at-risk FHRT. In addition, assessment of level of concern demonstrated moderate intraobserver agreement for control FHRT but lowered to only slight agreement for at-risk FHRT. Conclusions The simultaneous presentation of fetal heart rate tracings with maternal heart rate tracings introduces both intraobserver and interobserver variances in interpretation of decelerations and overall level of concern, particularly for at-risk FHRT. These changes in interpretation are likely due to the influence of subconscious perceptual decision-making and additional cognitive load in separating multiple streams of information. This may theoretically affect outcomes in cases in which visual information is nuanced. Medical professionals may want to exercise caution when adding more than one tracing to the visual array, as it may affect decision-making.

The maternal and fetal effects of smoking tobacco or non-tobacco cigarettes were studied in 75 pregnant patients and compared with a matched control group of 22 pregnant patients who did not smoke. The increase in maternal heart rate, maternal mean arterial pressure and fetal heart rate, and decrease in fetal heart rate 'baseline variability' and in fetal movements, were shown to be due primarily to the nicotine content of the cigarette.

Spatio-temporal spectral analysis of intracerebrally recorded seizure activity : T.M. Darcey, H.P. Meles and H.G. Wieser (Zürich, Switzerland)

Studies of maternal-fetal interaction during the last trimester of pregnancy: Ontogenesis of the basic rest-activity cycle

Objective. The addition of ST waveform analysis (STAN, Neoventa, Sweden) to fetal heart rate (FHR) tracings has been demonstrated to improve fetal outcome and reduce operative delivery rates, though the actual level of fetal acidosis at which STAN indicates intervention has not been assessed. We sought to determine if FHR ST segment analysis recommends intervention at appropriate levels of fetal acidosis.Methods. FHR tracings of 10 acidotic and 10 non-acidotic infants with FHR tracings having a minimum of one STAN flag were retrospectively analyzed. Fetal base deficit (BD) was calculated by interpolation throughout the FHR tracing and STAN ‘action’ and ‘ignore’ flags assigned a fetal BD value. A secondary analysis was performed with a revised interpretation of FHR reassuring status.Results. The mean (±SD) BD of the first STAN action was significantly greater than the first ‘ignore’ (4.0 ± 2.1 vs. 3.0 ± 0.8 mmol/L, p < 0.05). Clarified STAN criteria for reassuring vs. non-reassuring FHR resulted in a first action BD of 6.0 ± 2.0 mmol/L with 90% sensitivity and 100% specificity for prediction of fetal acidosis.Conclusion. The STAN monitor discriminates increasing levels of fetal BD. With clarification of the criteria for reassuring FHR, the calculated BDs of action flags are an appropriate threshold for emergent intervention, successfully predict acidotic fetuses, and avoid unnecessary intervention.

Novel Method for Fetal and Maternal Heart Rate Measurements Using 2-D Ultrasound Color Doppler Flow Images.

We attempted to shed light on the characterization and control of fetal arterial pressure and fetal heart rate in the chronically catheterized fetal lamb. To do this we continuously recorded fetal and maternal arterial pressures and heart rates as well as amniotic fluid pressures using on-line computer techniques. The data were analyzed for histogram distributions, correlations and regressions, and for intrinsic rhythms within each variable. We found the following: 1) neither fetal nor maternal variables are normally distributed because of an exaggerated mode and frequent skewing to the right, 2) there was no correlation between fetal and maternal variables over time periods of 10 min to 24 h, 3) a positive correlation exists between fetal arterial pressure and fetal heart rate, 4) there were no major rhythms in the fetal or maternal variables or in amniotic fluid pressure with cycles between 10 min and 24 h. The data suggest that 1) fetal arterial pressure and heart rate are largely independent of the mother, 2) fetal and maternal variables are well controlled about a physiological set point, and 3) rhythms in fetal arterial pressure and heart rate are not significant under normal laboratory conditions.

EFFECTS OF EXTRADURAL ANAESTHESIA ON UMBILICAL AND UTEROPLACENTAL ARTERIAL FLOW VELOCITY WAVEFORMS

THERE have been several reports of respiratory depression occurring in association with combined spinal epidural (CSE) analgesic techniques. 1-3 Intravenous fentanyl has been commonly administered in our institution to laboring women who either do not desire epidural analgesia or request analgesia before placement of an epidural catheter. The use of intrathecal sufentanil (ITS) plus low dose bupivacaine in CSE techniques for labor analgesia has become popular, although the use of CSE analgesia techniques may increase the risk of respiratory depression if administered after intravenous opioids have been previously given. We report one case of maternal respiratory arrest and one case of maternal respiratory arrest and severe hypotension, both accompanied by fetal distress, in two parturients who received ITS and bupivacaine after intravenous fentanyl.

Listening to patients and obtaining a thorough history are fundamental in clinical practice. Some pregnant women, particularly in late or preterm gestation, report regular, painful uterine contractions that may not correspond to true labor. In some cases, patients admitted to feigning contractions using the Valsalva maneuver to gain secondary benefits. Misdiagnosing such cases may lead to unnecessary interventions, including iatrogenic prematurity. To explore the phenomenon of pseudo-uterine contractions and assess whether maternal heart rate (HR) can help differentiate them from true contractions. We performed a prospective case-crossover study, which included 30 pregnant women in their third trimester who presented to Rambam Health Care Campus. Participants underwent 20 minutes of standard external monitoring followed by 10 minutes of repeated Valsalva maneuvers (every 2 minutes). Maternal and fetal HRs were recorded and compared during baseline, pseudo-, and true contractions. During pseudo-contractions, maternal HR decreased by approximately 10 bpm (P < 0.001), while fetal HR increased by 8 bpm (P < 0.001). In contrast, true contractions resulted in a maternal HR increase of 15 bpm (P < 0.001) and a fetal HR rise of 12 bpm (P < 0.001). Maternal HR patterns differ significantly between true and false contractions. A decline in maternal HR during contractions may indicate Valsalva-induced pseudo-contractions, while an increase suggests true labor. This simple observation could aid in preventing unnecessary interventions in suspected cases.

Purpose: Birth by cesarean delivery is a major public health issue with nearly one in three births delivered by cesarean section. Cesarean birth may be necessary to save mother or baby, but the rapid rise since 1996 without concomitant reduction in maternal and neonatal morbidity and mortality may indicate this mode of delivery may be over utilized. Cesarean births pose significant maternal and newborn health risks. Identification of factors that may contribute to reduction in the first cesarean birth in low-risk women who are nulliparous, term gestation, with single fetus in head down position (NTSV) is a health priority. The purpose of this study was two-fold: (1) to examine nursing assessment of fetal heart rate (FHR) tracing and their interventions (nursing surveillance) in response to identification of an FHR tracing consistent with category II pattern and (2) to identify whether nursing surveillance and frequency of category II patterns contribute to the risk of cesarean birth in NTSV women. Methodology: A descriptive, cross-sectional, correlational research design with purposive sample was used. Retrospective review of patient's electronic medical record was conducted for NTSV women who delivered at a large tertiary women's hospital between May and June 2013. Results: Statistically significant relationships were found between maternal age, admission BMI, induced labor, and cesarean birth. The odds of having a cesarean delivery was 12% (OR = 1.12) higher among women who had an increased number of nursing interventions within four hours prior to delivery. However, when examining the type of nursing intervention, none of the nursing interventions entered into the model were statistically significant as predictors of cesarean delivery. There was statistical significance between women who delivered vaginally and those who delivered by cesarean when examining nursing documentation of frequency of category II FHR tracing and nursing interventions. Conclusions: The primary aims of this research study were to examine if nursing identification of a category II FHR pattern and nursing interventions were predictors of cesarean birth. The presence of category II FHR pattern was not a predictor but frequency of nursing interventions was a statistically significant predictor when entered into a logistic regression model.

Effect of intravenous glucose injection on human maternal and fetal heart rate at term

128: Comparison of fetal ECG and standard external Doppler monitoring performance during second stage of labor

Fetal wellbeing during labor and delivery is commonly monitored through the cardiotocogram (CTG), the combined registration of uterus contractions and fetal heart rate (FHR). From the CTG, the fetal oxygen state is estimated as the main indicator of the fetal condition. However, this estimate is difficult to make, due to the complex relation between CTG and oxygen state. Mathematical models can be used to assist in interpretation of the CTG, since they enable quantitative modeling of the flow of events through which uterine contractions affect fetal oxygenation and FHR. This thesis describes the development of a model that can be used to reproduce FHR response to uterine contractions during several clinical scenarios. First, a model was developed that describes the relation between uterine contractions, maternal and fetal hemodynamics, oxygen distribution within the feto-maternal circulation and cardiovascular (reflex) regulation in the fetus in response to deviations in blood- and oxygen pressures. The model is partly based on previously presented models for cardiac function, chemoreceptor control in adults and oxygen distribution in the fetal circulation. These modules are coupled and scaled to meet requirements for the (pregnant) maternal and fetal condition. The model is completed with a module for uterine contractions and a module of the vascular system of both mother and fetus. A first clinical scenario was simulated with the model to test model response to changes in cerebral blood flow during the descent of the fetal head in the birth canal. A validation pilot was performed to investigate the quality of model outcome via expert opinion. Experts were unable to discriminate between real and simulated signals, suggesting that the model can be used for educational training. Second, the model was extended with the baroreceptor reflex. This allowed simulation of a second clinical scenario, where both chemo- and baroreflex pathways lead to a FHR deceleration in response to uterine flow reduction during contractions. Results for the uncompromised fetus show that partial oxygen pressures reduce in relation to the strength and duration of the contraction. Furthermore, decelerations during several scenarios of uteroplacental insufficiency were studied. Results for reduced uterine blood supply or reduced placental diffusion capacity, demonstrated lower baseline FHR and smaller decelarations during contraction. Reduced uteroplacental blood volume was found to lead to deeper decelerations only. The model response in several nerve blocking simulations is similar to experimental findings. Third, the model was used to simulate a third type of decelerations, i.e. variable heart rate decelerations, originating from umbilical cord compression. Different degrees of compression were investigated. An increase in contraction amplitude and duration leads to increased umbilical cord compression grade and thus affects the extent of blood pressure increase, flow redistribution and FHR response. There is a clear relation between fetal oxygenation, blood pressure and the resulting FHR. The extent of umbilical compression and thus FHR deceleration is positively related to increased contraction duration and amplitude, and increased sensitivity of the umbilical resistance to uterine pressure. Fourth, gynaecologists, midwives and residents were asked to rate a set of both model-generated CTGs and real CTGs for the three clinical scenarios. Although real tracings were more likely to be recognized correctly, the suitability for use in simulation training was found to be almost equal for real and computer-generated tracings. Due to limited numbers for early and variable deceleration evaluation, statistical analysis turned out to be valid only for the CTG’s with late decelerations. Additional comments from the respondents revealed that variability and regularity of the simulated signals greatly influence the perception of a tracing. Clinicians agreed that a tracing is suitable for use in simulation training when it is clear and free of physiological incompatibilities, which is the case for all simulated tracings. Fifth, the model was used to test the clinical hypothesis that administration of oxygen to the mother may increase FHR during variable fetal heart rate decelerations. The model was used to test the response of fetal oxygenation and heart rate to maternal oxygen increase following 100% oxygen administration. Model outcome suggests that FHR benefits from oxygen administration as the duration and depth of FHR decelerations and fetal oxygenation improves. However, the beneficial effect of maternal hyperoxygenation on FHR and oxygenation reduces during more severe variable decelerations. In conclusion, a model was developed to simulate the physiologic cascade from uterine contraction to changes in fetal heart rate. Model outcome for various scenarios is in correspondence with findings from animal experiments. The model can be used in an educational setting for the simulation of short-term changes in fetal hemodynamics and oxygenation status in response to uterine contractions to increase insight into the complex physiology. In addition, it can be integrated in a full-body delivery simulator to enhance obstetric team training.

A real-time algorithm has been developed for the simultaneous measurement of the fetal and maternal heart rates from the abdominal signal, which was sampled with 13-bit resolution at 500 Hz. The algorithm is based on digital filtering, adaptive thresholding, differencing of local maxima and minima and statistical properties in the time domain. The technique has been developed through a combination and modification of earlier techniques. The algorithm is found to be effective in resolving the fetal heart rate (FHR) when the fetal R waves and that of the maternal are overlapped. The algorithm has been tested on recorded ambulatory data from 36 to 41 gestational weeks of pregnancy, resulting in an average accuracy of 82% (min, 68%) for the fetal heart rate detection. A microcontroller based system has been developed and the proposed algorithm implemented in real-time. The above system is capable of continuous ambulatory FHR monitoring.