Objective Tocodynamometry (Toco—strain gauge technology) provides contraction frequency and approximate duration of labor contractions, but suffers frequent signal dropout necessitating re-positioning by a nurse, and may fail in obese patients. The alternative invasive intrauterine pressure catheter (IUPC) is more reliable and adds contraction pressure information, but requires ruptured membranes and introduces small risks of infection and abruption. Electrohysterography (EHG) reports the electrical activity of the uterus through electrodes placed on the maternal abdomen. This study compared all three methods of contraction detection simultaneously in laboring women. Study Design Upon consent, laboring women were monitored simultaneously with Toco, EHG, and IUPC. Contraction curves were generated in real-time for the EHG and all three curves were stored electronically. A contraction detection algorithm was used to compare frequency and timing between methods. Seventy-three subjects were enrolled in the study; 14 were excluded due to hardware failure of one or more of the devices (12) or inadequate data collection duration(2). Results In comparison with the gold-standard IUPC, EHG performed significantly better than Toco with regard to Contractions Consistency Index (CCI). The mean CCI for EHG was 0.88 ± 0.17 compared to 0.69 ± 0.27 for Toco (p<.0001). In contrast to Toco, EHG was not significantly affected by obesity. Conclusion Toco does not correlate well with the gold-standard IUPC and fails more frequently in obese patients. EHG provides a reliable non-invasive alternative regardless of body habitus.

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The popularity of the problem-based learning paradigm has stimulated new interest in small group, interactive teaching techniques. Medical educators of physiology have long recognized the value of such methods, using animal-based laboratories to demonstrate difficult physiological principles. Due to ethical and other concerns, a replacement of this teaching tool has been sought. Here, the author describes the use of a full-scale human patient simulator for such a workshop. The simulator is a life-size mannequin with physical findings (palpable pulses, breath/heart sounds, blinking eyes, etc.) and sophisticated mechanical and software models of the cardiovascular and pulmonary systems. It can be connected to standard physiological monitors to reproduce a realistic clinical environment. In groups of 10, first-year medical students explore Starling's law of the heart, the physiology of the Valsalva maneuver, and the function of the baroreceptor in a clinically realistic context using the simulator. With the use of a novel pre-/postworkshop assessment instrument that included student confidence in their answers, student confidence improved for all questions and survey items following the simulator session (P < 0.0001). The students give these laboratory exercises uniformly superior evaluations with > 85% of the students rating the workshop "very good" or "excellent".

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The purpose of the study was to compare the accuracy of a noninvasive fetal heart rate monitor with that of ultrasound, using a fetal scalp electrode as the gold standard, in laboring women of varying body habitus, throughout labor and delivery. Laboring women requiring fetal scalp electrode were monitored simultaneously with the investigational device (noninvasive fetal ECG), ultrasound, and fetal scalp electrode. An algorithm extracted the fetal heart rate from the noninvasive fetal ECG signal. Each noninvasive device recording was compared with fetal scalp electrode with regard to reliability by positive percent agreement and accuracy by root mean squared error. Seventy-one women were included in this analysis. Positive percent agreement was 83.4 ± 15.4% for noninvasive fetal ECG and 62.4 ± 26.7% for ultrasound. The root mean squared error compared with fetal scalp electrode-derived fetal heart rate was 4.8 ± 2.0 bpm for noninvasive fetal ECG and 14.3 ± 8.2 bpm for ultrasound. The superiority of noninvasive fetal ECG was maintained for stages 1 and 2 of labor and increases in body mass index. Compared with fetal scalp electrode-derived fetal heart rate, noninvasive fetal ECG is more accurate and reliable than ultrasound for intrapartum monitoring for stages 1 and 2 of labor and is less affected by increasing maternal body mass index. This confirms the results of other workers in this field.

We propose a method of predicting intrauterine pressure (IUP) from external electrohysterograms (EHG) using a causal FIR Wiener filter. IUP and 8-channel EHG data were collected simultaneously from 14 laboring patients at term, and prediction models were trained and tested using 10-min windows for each patient and channel. RMS prediction error varied between 5-14 mmHg across all patients. We performed a 4-way analysis of variance on the RMS error, which varied across patients, channels, time (test window) and model (train window). The patient-channel interaction was the most significant factor while channel alone was not significant, indicating that different channels produced significantly different RMS errors depending on the patient. The channel-time factor was significant due to single-channel bursty noise, while time was a significant factor due to multichannel bursty noise. The time-model interaction was not significant, supporting the assumption that the random process generating the IUP and EHG signals was stationary. The results demonstrate the capabilities of optimal linear filter in predicting IUP from external EHG and offer insight into the factors that affect prediction error of IUP from multichannel EHG recordings.

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Maternal analgesia and sedation with fentanyl (1 microg x kg(-1)) and midazolam (0.02 mg x kg(-1)) immediately prior to spinal anesthesia is not associated with adverse neonatal effects.