Experimental study of an asymmetric valveless pump to elucidate insights into strategies for pediatric extravascular flow augmentation.

Asymmetric pumping is a sub-category of valveless pumping in which a flexible tube is rhythmically compressed in the transverse symmetry plane. Due to the resulting asymmetry between the suction and discharge pipes, a net pumping head is achieved. Asymmetric pumping is regarded as one of the main mechanisms responsible for the Liebau effect in addition to impedance pumping. However, there remains a paucity of research surrounding the governing parameters of asymmetric pumping. Here, we conducted an experimental study of the performance of an asymmetric pump, with an aim to assess its potential for extravascular flow augmentation. A custom flexible latex tube and experimental platform were developed for this purpose. We tested various tube thicknesses and pinching frequencies. Our results demonstrate that the performance is within the range of physiological requirements for pediatric circulatory devices (~ 1 L/min and < 30 mmHg). We conclude that due to the absence of reverse flow and its mechanical simplicity, pure asymmetric pumping is promising for selected cardiovascular applications with less complexity than other valveless techniques.

Benchmark for Numerical Models of Stented Coronary Bifurcation Flow.

In-stent restenosis ails many patients who have undergone stenting. When the stented artery is a bifurcation, the intervention is particularly critical because of the complex stent geometry involved in these structures. Computational fluid dynamics (CFD) has been shown to be an effective approach when modeling blood flow behavior and understanding the mechanisms that underlie in-stent restenosis. However, these CFD models require validation through experimental data in order to be reliable. It is with this purpose in mind that we performed particle image velocimetry (PIV) measurements of velocity fields within flows through a simplified coronary bifurcation. Although the flow in this simplified bifurcation differs from the actual blood flow, it emulates the main fluid dynamic mechanisms found in hemodynamic flow. Experimental measurements were performed for several stenting techniques in both steady and unsteady flow conditions. The test conditions were strictly controlled, and uncertainty was accurately predicted. The results obtained in this research represent readily accessible, easy to emulate, detailed velocity fields and geometry, and they have been successfully used to validate our numerical model. These data can be used as a benchmark for further development of numerical CFD modeling in terms of comparison of the main flow pattern characteristics.

Effects of bifurcation-specific and conventional stents on coronary bifurcation flow. An experimental and numerical study.

Our paper builds on existing research into conventional bare metal stents in order to assess new devices specifically designed for coronary bifurcation angioplasty. The first aim is to validate the numerical model against data from in vitro experiments on stented coronary phantoms. A surface mesh was built in accordance with micro-computed tomography images obtained from coronary stents implanted in silicone models and used for numerical analysis. Computational simulations for steady and unsteady cases generally agreed with their experimental counterparts. A second objective is to compare the hemodynamic performance of one of these new devices (Stentys) to that of conventional devices and stenting techniques in a simplified coronary bifurcation model. Four different coronary bifurcation stenting techniques were analyzed. We have focused on factors contributing to restenosis, such as wall shear stress (WSS), oscillatory shear index (OSI), pressure loss, and local normalized helicity (LNH). It was found that bifurcation-specific stents implanted in the side branch led to increased malapposition. This effect has proved to be more important than stent specific design characteristics such as strut size (different for conventional and Stentys stent). This conclusion is confirmed by means of drop in pressure and mechanical energy loss rate calculation; for the latter, the increase ranged from 9% to 17%, depending on the stenting technique, when dedicated stents were implanted in the side branch. The behavior patterns presented in this study should be double-checked against those obtained in more realistic geometries.

Numerical Study of Blood Clots Influence on the Flow Pattern and Platelet Activation on a Stented Bifurcation Model.

Stent implantation is a common procedure followed in arteries affected by atherosclerosis. This procedure can lead to other stenting-related problems. One of these is the deposition and accumulation of blood clots over stent struts. This process can have further consequences, in so far as it can introduce modifications to the flow pattern. This problem is especially critical in stented bifurcations, where resulting stent geometry is more complex. In this regard, a numerical study is presented of the effect on the flow pattern and platelet activation of blood clot depositions on the stent struts of a stented coronary bifurcation. The numerical model is first validated with experimental measurements performed for this purpose. Experiments considered a flow with suspended artificial thrombi, which naturally deposited on stent struts. The location and shape observed were used to create numerical thrombi. Following this, numerical simulations were performed to analyze the influence of the presence of thrombi depositions on parameters such as Time Averaged Wall Shear Stress, Oscillatory Shear Index or Relative Residence Time. Finally, a study was also carried out of the effect of different geometrical configurations, from a straight tube to a stented bifurcation model with thrombus depositions, on platelet activation.

Indicadores de energía térmica enlos horpitales de Castilla y León / Indicators of thermal energy in the hospitals of Castilla y Leon

Se trata en este trabajo de btener indicdores energéticos de calefacción y ACS por periodos de tiempo equivalentes que sean independientes de a ubicación y de la diensión del hospital. La desviación de los indicacores de cada hospital con respecto a los indicacores obtenidos como media de los hospitales de Catella y León - indicadores de referencia – permitirá extraer concluisones sobre el estados de las instalaciones, el funciomnamiento y la bondd térmica del edificio. Este primer análisis de los indicadores de energía térmica se realizará en base a los datos de la Auditorías Energéticas realizadas en los hospitales de Castilla y León. Los indicadores de energía térmica anuales, y en todos ellos se intentará ponderar el valor con el año tipo climatológico para evitar la aleatoriedaes climatológicas. Dada la diferencia de servicios y de actividad que los hospitales de castilla y León titne por tamaño, se ha considerado en este trabajo la tipoogía de grandes hospitales conmás de 300 camas (AU)

Through this work, the authors have proposed to obtain indicators and DHW heating energy for equivalent time periods that are independent of the location and size of the hospital The deviation of the indictors for each hospital with respect to indicators of the average obtained from hospitals in Castilla y Leon bench marks “will draw conclusions about the state of the facilities, operation and building thermal goodness (AU)

[Computational fluid dynamics simulations of the airflow in the human nasal cavity]. / Análisis del flujo aéreo en la cavidad nasal mediante Mecánica de Fluidos Computacional.

OBJECTIVE: This study represents an attempt to simulate the complex three-dimensional airflow pattern in the human nasal passageways. MATERIALS AND METHODS: In the present study the computational Fluid Dynamics (CFD) have been used. The CFD solved numerically the flow governing equations. The CFD demonstrated to be a very efficient tool for researching on nasal flow. RESULTS: By means of CT scan, an anatomic accurate three-dimensional representation of the human nasal cavity was obtained. Based on this model the influence of the inspiration and at the expiration at the flow pattern has been reviewed. The flow pattern is visualized by the velocity, pressure and turbulence intensity fields. CONCLUSIONS: The flow patterns show the channel effect of turbinates and the influence of the breathing phase.

Análisis del flujo aéreo en la cavidad nasal mediante Mecánica de Fluidos Computacional / Computational fluid dynamics simulations of the airflow in the human nasal cavity

Objetivo: El objetivo de este trabajo es visualizar y analizar el flujo aéreo a través de la cavidad nasal de forma computarizada. Material y métodos: Se utiliza una aproximación alternativa y novedosa llamada Mecánica de Fluidos Computacional (MFC) que ha demostrado ser una herramienta muy poderosa para el estudio de la dinámica de fluidos. Esta técnica consiste en simular cómo se mueve el aire bajo unas determinadas condiciones de contorno. Resultados: Se realiza el modelo numérico de la cavidad nasal anatómicamente exacta basándonos en la anatomía (imágenes de TC) y en la fisiología nasal. Se visualiza el flujo aéreo en las dos fases de la respiración y se observan las líneas de corriente, los perfiles de velocidad y los campos de presión y de intensidad de turbulencia. Conclusiones: Se demuestra el efecto de guiado de los cornetes, la distribución laminar del flujo y la influencia de la fase de la respiración en el patrón del flujo (AU)

Objective: This study represents an attempt to simulate the complex three-dimensional airflow pattern in the human nasal passageways. Materials and methods: In the present study the computational Fluid Dynamics (CFD) have been used. The CFD solved numerically the flow governing quations. The CFD demonstrated to be a very efficient tool for researching on nasal flow. Results: By means of CT scan, an anatomic accurate three-dimensional representation of the human nasal cavity was obtained. Based on this model the influence of the inspiration and at the expiration at the flow pattern has been reviewed. The flow pattern is visualized by the velocity, pressure and turbulence intensity fields. Conclusions: The flow patterns show the channel effect of turbinates and the influence of the breathing phase (AU)