Envelope Analysis of the Human Alpha Rhythm Reveals EEG Gaussianity.

OBJECTIVE: To assess the Gaussianity of the human alpha rhythm using the envelope signal and the coefficient of variation of the envelope (CVE). METHODS: Envelope analysis relies on the fact that the CVE for Gaussian noise is √{(4-π)/π} ≈ 0.523. CVE can thus be used as a hallmark to detect Gaussianity, and any significant deviation from Gaussianity can be linked to synchronous neural dynamics. We applied envelope analysis to EEG and iEEG public databases. RESULTS: The human alpha rhythm can be characterized either as a synchronous or as a Gaussian signal based on the value of its CVE. Furthermore, Fourier analysis showed the canonical spectral peak at ≈ 10[Hz] is present in both the synchronous and Gaussian cases, thus demonstrating this same peak can be produced by different underlying neural dynamics. CONCLUSION: Human EEG can be classified using envelope parameters. This study confirms the original interpretation of Adrian regarding the origin of the alpha rhythm but also opens the door for the study of Gaussianity in brain dynamics. SIGNIFICANCE: Envelope analysis constitutes a novel complement to Fourier-based methods for neural signal analysis relating amplitude modulations (CVE) to signal energy. These results suggest a broader interpretation for event-related synchronization/desynchronization (ERS/ERD) may be needed.

Multi-scale Entropy Evaluates the Proarrhythmic Condition of Persistent Atrial Fibrillation Patients Predicting Early Failure of Electrical Cardioversion.

Atrial fibrillation (AF) is nowadays the most common cardiac arrhythmia, being associated with an increase in cardiovascular mortality and morbidity. When AF lasts for more than seven days, it is classified as persistent AF and external interventions are required for its termination. A well-established alternative for that purpose is electrical cardioversion (ECV). While ECV is able to initially restore sinus rhythm (SR) in more than 90% of patients, rates of AF recurrence as high as 20-30% have been found after only a few weeks of follow-up. Hence, new methods for evaluating the proarrhythmic condition of a patient before the intervention can serve as efficient predictors about the high risk of early failure of ECV, thus facilitating optimal management of AF patients. Among the wide variety of predictors that have been proposed to date, those based on estimating organization of the fibrillatory (f-) waves from the surface electrocardiogram (ECG) have reported very promising results. However, the existing methods are based on traditional entropy measures, which only assess a single time scale and often are unable to fully characterize the dynamics generated by highly complex systems, such as the heart during AF. The present work then explores whether a multi-scale entropy (MSE) analysis of the f-waves may provide early prediction of AF recurrence after ECV. In addition to the common MSE, two improved versions have also been analyzed, composite MSE (CMSE) and refined MSE (RMSE). When analyzing 70 patients under ECV, of which 31 maintained SR and 39 relapsed to AF after a four week follow-up, the three methods provided similar performance. However, RMSE reported a slightly better discriminant ability of 86%, thus improving the other multi-scale-based outcomes by 3-9% and other previously proposed predictors of ECV by 15-30%. This outcome suggests that investigation of dynamics at large time scales yields novel insights about the underlying complex processes generating f-waves, which could provide individual proarrhythmic condition estimation, thus improving preoperative predictions of ECV early failure.

Comparación del volumen y composición del calostro extraído con una bomba manual o eléctrica / Volumen and composition comparison of human foremilk extracted with manual of electrical pump

Introducción. Objetivo: conocer el efecto sobre el tiempo, volumen y composición de leche humana, cuando para obtenerla se emplea una bomba manual o eléctrica. Material y métodos. Se efectuaron 3 estudios en madres sanas que cursaban la primera semana poscesárea; se midió el tiempo y el volumen de leche obtenido, desde que se inició el goteo hasta que cesó espontáneamente. En el primer estudio, de 85 madres, se extrajo leche con bomba manual (BM) en 129 ocasiones; el mismo procedimiento se efectuó con bomba eléctrica (BE) en 86 madres en 180 ocasiones. En el segundo estudio, a 30 madres se les extrajo leche con BM del pecho izquierdo y del pecho derecho con BE; y en el tercero participaron 22 madres, en quienes se obtuvo la leche de ambos pechos primero con BM y para conocer las características de la leche residual, se aplicó la BE. En los dos últimos estudios se midió la concentración de proteína, lípido e hidratos de carbono en la leche. Resultados. El tiempo empleado en la obtensión de la leche de ambos pechos fue semejante usando BM o BE. En todos los estudios el volumen de leche extraído fue sistemáticamente menor cuando se utilizó BM (P < 0.01). En el segundo estudio la concentración de lípidos de la leche obtenida del pecho izquierdo con BM y del derecho con BE fue semejante. En el tercer estudio, la leche inicial tuvo una concentración de lípidos de 1.6 en tanto que la residual obtenida con BE tuvo una concentración de 2.1 g/dL (P < 0.05). Conslusión. La leche extraída con BM tiene menor volumen que la obtenida con BE, con una composición que semeja más a la leche frontal; la extraída con BE tiene una composición más cercana a la leche escondida, siendo por su volumen y composición más apropiada para nutrir a los niños