Dielectric elastomer actuator-based valveless pump as Fontan failure assist device: introduction and preliminary study.

OBJECTIVES: Fontan failure refers to a condition in which the Fontan circulation, a surgical procedure used to treat certain congenital heart defects, becomes insufficient, leading to compromised cardiac function and potential complications. This in vitro study therefore investigates the feasibility of bladeless impedance-driven cavopulmonary assist device via dielectric elastomer actuator (DEA) as a means to address Fontan failure. METHODS: A cavopulmonary assist device, constructed using DEA technologies and employing the impedance pump concept, is subjected to in vitro testing within a closed-loop setup. This study aims to assess the device's functionality and performance under controlled conditions, providing valuable insights into its potential application as a cavopulmonary assistive technology. RESULTS: The DEA-based pump, measuring 50 mm in length and 30 mm in diameter, is capable of achieving substantial flow rates within a closed-loop setup, reaching up to 1.20 l/min at an activation frequency of 4 Hz. It also provides a broad range of working internal pressures (<10 to >20 mmHg). Lastly, the properties of the flow (direction, magnitude, etc.) can be controlled by adjusting the input signal parameters (frequency, amplitude, etc.). CONCLUSIONS: In summary, the results suggest that the valveless impedance-driven pump utilizing DEA technology is promising in the context of cavopulmonary assist devices. Further research and development in this area may lead to innovative and potentially more effective solutions for assisting the right heart, ultimately benefiting patients with heart-related health issues overall, with a particular focus on those experiencing Fontan failure.

Novel para-aortic cardiac assistance using a pre-stretched dielectric elastomer actuator.

OBJECTIVES: We propose an evolution of a dielectric elastomer actuator-based cardiac assist device that acts as a counterpulsation system. We introduce a new pre-stretched actuator and implant the device in a graft bypass between the ascending and descending aorta to redirect all blood through the device (ascending aorta clamped). The objective was to evaluate the influence of these changes on the assistance provided to the heart. METHODS: The novel para-aortic device and the new implantation technique were tested in vivo in 5 pigs. We monitored the pressure and flow in the aorta as well as the pressure-volume characteristics of the left ventricle. Different activation timings were tested to identify the optimal device actuation. RESULTS: The proposed device helps reducing the end-diastolic pressure in the aorta by up to 13 ± 4.0% as well as the peak systolic pressure by up to 16 ± 3.6%. The early diastolic pressure was also increased up to 10 ± 3.5%. With different activation, we also showed that the device could increase or decrease the stroke volume. CONCLUSIONS: The new setup and the novel para-aortic device presented here helped improve cardiac assistance compared to previous studies. Moreover, we revealed a new way to assist the heart by actuating the device at different starting time to modify the left ventricular stroke volume and stroke work.

Dielectric Elastomer Actuator-Based Valveless Impedance-Driven Pumping for Meso- and Macroscale Applications.

Impedance pumps are simple designs that allow the generation or amplification of flow. They are fluid-filled systems based on flexible tubing connected to tubing with different impedances. A periodic off-center compression of the flexible tubing causes the fluid to move and generate flow. Wave reflection at the impedance mismatch is the primary driving mechanism of the flow. In addition to their straightforward design, impedance pumps are bladeless, valveless, and pulsatile. These properties are highly sought after by demanding and challenging applications, such as the biomedical field, as they present less risk of damage, disruption, and obstruction when handling viscous and delicate fluids/matter. In this study, we propose a high-performance impedance-driven pumping concept with embedded actuation based on a multilayered tubular dielectric elastomer. This pumping system is made of three parts, a dielectric elastomer actuator tube, a passive tube, and a rigid ring that binds and decouples the two subsystems. The system is able to generate net fluid flow rates up to 1.35 L/min with an internal pressure of 125 mmHg. The soft simplistic design, self-contained concept, and high performances of these pumping systems could make them disruptive in many challenging meso- and macroscale applications in general and in the biomedical field in particular.

Hemodynamic effects of a dielectric elastomer augmented aorta on aortic wave intensity: An in-vivo study.

Dielectric elastomer actuator augmented aorta (DEA) represents a novel approach with high potential for assisting a failing heart. The soft tubular device replaces a section of the aorta and increases its diameter when activated. The hemodynamic interaction between the DEA and the left ventricle (LV) has not been investigated with wave intensity (WI) analysis before. The objective of this study is to investigate the hemodynamic effects of the DEA on the aortic WI pattern. WI was calculated from aortic pressure and flow measured in-vivo in the descending aorta of two pigs implanted with DEAs. The DEAs were tested for different actuation phase shifts (PS). The DEA generated two decompression waves (traveling upstream and downstream of the device) at activation followed by two compression waves at deactivation. Depending on the PS, the end-diastolic pressure (EDP) decreased by 7% (or increased by 5-6%). The average early diastolic pressure augmentation (Pdia¯) increased by 2% (or decreased by 2-3%). The hydraulic work (WH) measured in the aorta decreased by 2% (or increased by 5%). The DEA-generated waves interfered with the LV-generated waves, and the timing of the waves affected the hemodynamic effect of the device. For the best actuation timing the upstream decompression wave arrived just before aortic valve opening and the upstream compression wave arrived just before aortic valve closure leading to a decreased EDP, an increased Pdia¯ and a reduced.WH.

A novel soft cardiac assist device based on a dielectric elastomer augmented aorta: An in vivo study.

Although heart transplant is the preferred solution for patients suffering from heart failures, cardiac assist devices remain key substitute therapies. Among them, aortic augmentation using dielectric elastomer actuators (DEAs) might be an alternative technological application for the future. The electrically driven actuator does not require bulky pneumatic elements (such as conventional intra-aortic balloon pumps) and conforms tightly to the aorta thanks to the manufacturing method presented here. In this study, the proposed DEA-based device replaces a section of the aorta and acts as a counterpulsation device. The feasibility and validation of in vivo implantation of the device into the descending aorta in a porcine model, and the level of support provided to the heart are investigated. Additionally, the influence of the activation profile and delay compared to the start of systole is studied. We demonstrate that an activation of the DEA just before the start of systole (30 ms at 100 bpm) and deactivation just after the start of diastole (0-30 ms) leads to an optimal assistance of the heart with a maximum energy provided by the DEA. The end-diastolic and left ventricular pressures were lowered by up to 5% and 1%, respectively, compared to baseline. The early diastolic pressure was augmented in average by up to 2%.

Incidencia del VIH-SIDA y su relación con el incremento del trabajo sexual comercial en la ciudad de La Paz en el periódo / Incidence of the HIV-AIDS and their relationship with the increment of the work sexual commercial in the city of The Peace in the period

El sexo ha estado en venta a través de todas las épocas, y sin embargo es obio que las foras actuales del comerció sexual, se hallan muy alejadas de las que se tuvo en el pasado, ya que hoy el sexo es comercializado por internet y prensa, convirtiéndose en una alternativa para muchas mujeres que obtienen dinero sin necesidad de una formación (estudios, profesión). La inquetud pra realizar esta investigación, radica en los informes contradictorios acerca del número de personas que viven con VIH-SIDA (PVVS), y la persistencia de la idea de que esta problematica se halla circunscrita a grupos en riesgo, ignorando que gran part de esta población, son también madres de familia, y tienen de una u otra forma un núcleo familiar, que se ve inmerso en este fenómeno biopsicosocial. Al ser un proyecto de investigación, destinado a identificar los factores causales para el aumento de la incidencia del VIH-SIDA y la relación con el trabjo sexual comercial (TSC); se realizó un estudio descriptivo retrospectivo en la población denominada en situación de riesgo en la ciudad de La Paz en el periódo de 1999-2003. El universo está constituido por 1750 TSC registradas entre enero de 1999, hasta diciembre de 2003 y una muestra de 300, seleccionadas por conveniencia en forma no probabilística de las cuales se recolectó información mediante na encuesta prediseñada; con consentimiento informado, que permitió también identificar, tres causas importantes que las indujieron al trabajo sexual comercial: Económicas con 73.3 porcinto, falta de cúcleo familkiar 10 porciento y el abandono de pareja con un 6.6 porciento.

Efectividad de la técnica del paralelismo usando aditamento de precisión XCP en la toma de radiografías por los estudiantes de las clínicas intramurales de la facultad de odontología de la Universidad de El Salvador en un período de septiembre a noviembre de 1998 / Effectiveness of the parallelism technique using XCP precision attachment in taking radiographs by students of the intramural clinics of the Faculty of Dentistry of the University of El Salvador in a period from September to November 1998

La presente investigación tiene como objetivo, mostrar la efectividad de la técnica de paralelismo con aditamentos de precisión XCP; en la toma de radiografías por los estudiantes de las clínicas intramurales de la facultad de odontología de la Universidad de El Salvador en un periodo de septiembre a noviembre de 1998. Dicha investigación consta de cinco fases donde la primera contiene el planteamiento del problema que enmarca la situación en la que se presentan todas aquellas circunstancias que hacen valedera la realización de esta investigación; como también todas aquellas dificultades que se presentan a laos estudiantes de odontología del área de diagnostico al realizar la toma de radiografías, también se presenta el enunciado del problema, el cual es el punto de partida para la realización de esta investigación, además esta fase consta de la justificación en donde se presentan todas aquellas razones por las cuales esta investigación amerita ser realizada; concluyendo esta fase con la presentación de los objetivos tanto general como específicos, alcances y limitaciones. La segunda fase se refiere al marco teórico, el cual está formado por antecedentes del tema de estudio. En la tercera fase se encuentra la formulación de la hipótesis en donde se plantea todas aquellas suposiciones que al ser demostradas permitirán la comprobación de los objetivos, además en esta fase se presentan las variables e indicadores en estudio y la definición operacional de dichas variables. En la cuarta fase se contempla la metodología que consta del tipo de investigación, la población en que fue realizada y como fueron seleccionadas, además contiene las técnicas e instrumentos realizados en la realización del experimento. En la quinta fase se encuentran los resultados obtenidos en la investigación, la comprobación de hipótesis a partir de estos resultados y las conclusiones tanto específicas como generales de la investigación, así como las recomendaciones hechas por los investigadores a partir de las conclusiones.

The present research aims to show the effectiveness of the parallelism technique with XCP precision attachments; in the taking of X-rays by the students of the intramural clinics of the Faculty of Dentistry of the University of El Salvador in a period from September to November 1998. Said investigation consists of five phases where the first contains the statement of the problem that frames the situation in which all those circumstances are presented that make the carrying out of this investigation valid; As well as all those difficulties that are presented to the dental students of the diagnostic area when taking X-rays, the statement of the problem is also presented, which is the starting point for the realization of this research, in addition this phase consists of of the justification in which all those reasons are presented for which this investigation deserves to be carried out; concluding this phase with the presentation of both general and specific objectives, scope and limitations. The second phase refers to the theoretical framework, which is formed by antecedents of the subject of study. In the third phase is the formulation of the hypothesis where all those assumptions are raised that when demonstrated will allow the verification of the objectives, also in this phase the variables and indicators under study and the operational definition of said variables are presented. In the fourth phase, the methodology that consists of the type of research, the population in which it was carried out and how they were selected, also contains the techniques and instruments used in carrying out the experiment. In the fifth phase are the results obtained in the research, the hypothesis testing based on these results and the specific and general conclusions of the research, as well as the recommendations made by the researchers based on the conclusions.