IEEE Engineering in Medicine and Biology Magazine最新文献

This work investigates the complex relationships between cerebrovascular dynamics, intracranial pressure (ICP), Cushing response, and short-term systemic regulation via an original mathematical model. The model has been used to analyze the effects of Cushing response on cardiovascular and cerebrovascular quantities during constant ICP elevation and during the occurrence of ICP plateau waves and to investigate the conditions leading to system instability with the formation of slow (0.05-0.1 Hz) arterial pressure waves. The model may be of value to assist clinicians in finding the balance between clinical benefits of Cushing response and its shortcomings.

Calculation of approximate entropy (ApEn) requires a priori determination of two unknown parameters, m and r. While the recommended values of r, in the range of 0.1¿0.2 times the standard deviation of the signal, have been shown to be applicable for a wide variety of signals, in certain cases, r values within this prescribed range can lead to an incorrect assessment of the complexity of a given signal. To circumvent this limitation, we recently advocated finding the maximum ApEn value by assessing all values of r from 0 to 1 and found that the maximum ApEn does not always occur within the prescribed range of r values. Our results indicate that finding the maximum ApEn leads to the correct interpretation of a signal's complexity. One major limitation, however, is that the calculation of all choices of r values is often impractical because of the computational burden. Our new method, based on a heuristic stochastic model, overcomes this computational burden and leads to the automatic selection of the maximum ApEn value for any given signal. On the basis of Monte Carlo simulations, we derive general equations that can be used to estimate the maximum ApEn with high accuracy for a given value of m. Application to both synthetic and experimental data confirmed the advantages claimed with the proposed approach.

In this article, we investigated the hypothesis that the effects of hypergravity on respiratory sinus arrhythmia (RSA) can mimic the effects observed after spaceflight cardiovascular deconditioning. Artificial gravity along the head-to-feet axis on a short-arm centrifuge induces gravity gradients. This physiological condition of significantly higher g at the feet than at the heart level is specific and likely induces blood sequestration in the lower limbs. After spaceflight, astronauts are in a condition of cardiovascular deconditioning, where blood pooling in the lower part of the body and autonomic adaptation are factors contributing to orthostatic intolerance and changes in heart-rate variability (HRV). ECG and respiration were recorded during imposed and controlled breathing (ICB) protocols, which were repeated at different levels of artificial gravity as well as during supine and standing control conditions, and the changes were analyzed.

The influence of maternal respiration on the occurrence of short-term fetal--maternal heart-rate coordination was examined using a model, which considers both heart-rate characteristics and effects of maternal respiratory sinus arrhythmia. Epochs of fetal--maternal heart-rate coordination were identified in model data produced at varying respiratory rates and compared with epochs found in real data acquired in mother-fetus pairs. The model results suggest that the low incidence of epochs found in the real data at low-breathing rates may be explained by heart-rate characteristics, but that the higher incidence at fast rates must be due to other factors.

The senior capstone design course is the culmination of the previous three years of the undergraduate curriculum. The goal of this course is to develop students' communication (oral and written), interpersonal, teamwork, analytical, design, and project management skills through a team-based design experience. Students learn about the product-development process and gain experience solving open-ended problems. Capstone design courses give students insight into what it is like to work as an engineer.

The cardiovascular system is composed of a variety of specialized subsystems that interact with each other under the influence of internal and external inputs, including central commands, reflex mechanisms, and humoral factors. The concomitant action of all these subsystems produces continuous adjustments in the cardiovascular variables (e.g., heart rate, heart contractility, blood pressure, vascular tone, etc.) referred to as cardiovascular variability. A large body of evidence indicates that this variability includes linear and nonlinear components and conveys important biological information that might help in the understanding of the underlying physiology and facilitate diagnosis and prognosis of cardiovascular dysfunctions.

This article aims to identify the potential indicators of obstructive apnea (OA) in the ECG, based on the traces of QRS area from multiple ECG leads. We compare the difference in these traces' phase relation found during and after each OA episode to the difference between the first and second half of the OA and between split halves of epochs of normal respiration (NR).

Previous studies suggested that gamma oscillations in the brain are associated with higher order cognitive functions, including selective visual attention, motor task planning, sensory perception, working memory, and dreaming rapid eye movement (REM) sleep. These oscillations are mainly observed in the cortical regions and also occur in neocortical and subcortical areas and hippocampus. These oscillations may occur under certain pathological conditions, such as epilepsy, and are mainly observed in the cortical regions and hippocampus. The previous studies have suggested that epilepsy may be associated with disturbances of autonomic nervous system(ANS) and with changes in autonomic cardioregulatory function. In this article, we investigate the influence of acute exposure to 2-aminoethoxy-diphenylborate (2-APB), a membrane-permeable inositol 1,4,5-trisphosphate (IP) receptor, and store-operated Ca(2+) channel (SOC) blocker on the complexity of hippocampal gamma oscillations. Our central hypothesis is that acute exposure to 2-APB significantly reduces the hippocampal gamma oscillations. To test this hypothesis, we use brain-slice recordings and the advanced nonlinear dynamical analysis method based on the Lempel-Ziv (LZ) estimator. Our nonlinear dynamical analysis results estimated from brain-slice recordings suggested that 2-APB exposure significantly reduces the hippocampal gamma oscillations.