RESUMEN
Monitoring fetal heart rate during pregnancy is essential to assist clinicians in making more timely decisions. Non-invasive monitoring of fetal heart activities using abdominal ECGs is useful for diagnosis of heart defects. However, the extracted fetal ECGs are usually too weak to be robustly detected. Thus, it is a necessity to enhance fetal R-peak since their peaks may be hidden within the signal due to the immaturity of the fetal cardiovascular system. Therefore, to improve the detection of the fetal heartbeat, a novel fetal R-peak enhancement technique was proposed to statistically generate the weighting mask according to the distribution of the neighboring temporal intervals between each pair of peaks. Two sets of simulations were designed to validate the reliability of the method: challenges with different levels of (1) noise contamination and (2) R-peak interval changing rate. The simulation results showed that the weighting mask improved the accuracy of the R-peak detection rate by 25% and decreased the false alarm rate by 20% with white noise contamination, and ensured high R-peak detection rate (>80%), especially with mild noise contamination (noise amplitude ratio <1.5 and noise rate per minute <25%). For the simulations with continuous R-peak intervals changing, the masking process can still effectively eliminate noise contamination especially when the amplitude of the sinusoidal fetal R-R intervals is lower than 50 ms. For the real fetus ECGs, the detection rate was increased by 3.498%, whereas the false alarm rate was decreased by 3.933%. Next, we implemented the fetal R-peak enhancement technique to investigate fractal regulation and multiscale entropy of the real fetal heartbeat intervals. Both scaling exponent (â¼0.6 to â¼1 in scale 4-15) and entropy measure (scale 6-10) increased with gestational ages (22-40 weeks). The results confirmed fractal slope and complexity of fetal heartbeat intervals can reflect the maturation of fetus organism.
Asunto(s)
Electrocardiografía/métodos , Monitoreo Fetal/métodos , Frecuencia Cardíaca Fetal/fisiología , Procesamiento de Señales Asistido por Computador , Algoritmos , Femenino , Edad Gestacional , Humanos , Embarazo , Reproducibilidad de los ResultadosRESUMEN
BACKGROUND: Medical students often learn the skills necessary to perform a central venous catheterization in the operating room after simulator training. We examined the performance of central venous catheterization by medical students from the logbooks during their rotation in department of anesthesiology. METHODS: From the logbooks of medical students rotating in our department between January 2011 and June 2012, we obtained the kind and the number of central venous catheterization students had done, the results of the procedures whether they were success or failed, the reasons of the failures, complications, and the student self-reported confidence and satisfaction of their performance. RESULTS: There were 93 medical students performed 875 central venous catheterizations with landmark guidance on patients in the operating theater, and the mean number of catheterizations performed per student was 9.4 ± 2.0, with a success rate of 67.3%. Adjusted for age, sex, body mass index, surgical category, ASA score and insertion site, the odds of successful catherization improved with cumulative practice (odds ratio 1.10 per additional central venous catheterization performed; 95% confidence interval 1.05-1.15). The major challenge students encountered during the procedure was the difficulty of finding the central veins, which led to 185 catheterizations failed. The complication rate of central venous catheterization by the students was 7.8%, while the most common complication was puncture of artery. The satisfaction and confidence of students regarding their performance increased with each additional procedure and decreased significantly if failure or complications had occurred. CONCLUSION: A student logbook is a useful tool for recording the actual procedural performance of students. From the logbooks, we could see the students' performance, challenges, satisfaction and confidence of central venous catheterization were improved through cumulative clinical practice of the procedure.