Electropneumatic system for the simulation of the pulmonary viscoelastic effect in a mechanical ventilation scenario.

The viscoelastic properties of the lung have important implications during respiratory mechanics in terms of lung movement or work of breathing, for example. However, this property has not been well characterized due to several reasons, such as the complex nature of the lung, difficulty accessing its tissues, and the lack of physical simulators that represent viscoelastic effects. This research proposes an electropneumatic system and a method to simulate the viscoelastic effect from temporary forces generated by the opposition of magnetic poles. The study was tested in a mechanical ventilation scenario with inspiratory pause, using a Hamilton-S1 mechanical ventilator (Hamilton Medical) and a simulator of the human respiratory system (SAMI-SII). The implemented system was able to simulate the stress relaxation response of a Standard Linear Solid model in the Maxwell form and showed the capacity to control elastic and viscous parameters independently. To the best of our knowledge, this is the first system incorporated into a physical lung simulator that represents the viscoelastic effect in a mechanical ventilation scenario.

Comparison of frictional resistance among conventional, active and passive selfligating brackets with different combinations of arch wires: a finite elements study.

The aim of this study was to compare frictional resistance among conventional, passive and active selfligating brackets using Finite Elements Analysis (FEA). Seventynine (79) slide tests were performed by combining an upper first bicuspid conventional bracket, 0.018" stainless steel wires and 0.010" ligature by means of an INSTRON 3345 load system to obtain average maximum static frictional resistance (MSFR). This value was compared to the FR (frictional resistance) obtained by simulation of a slide of the same combination by FEA following conventional bracket modeling by means of Computer Aided Design (CAD). Once the FEA was validated, bracket CADs were designed (upper right first bicuspid conventional, active and passive selfligating bracket) and bracket properties calculated. MSFR was compared among conventional, active and passive selfligating brackets with different alloys and archwire cross sections such as 0.018", 0.019" x 0.025"and 0.020" x 0.020". Passive selfligating brackets had the lowest MSFR, followed by conventional brackets and active selfligating brackets. In conventional brackets, a 0.018" archwire produced a linear pattern of stress with maximum concentration at the center. Conversely, stress in 0.020 x 0.020" and 0.019 x 0.025" archwires was distributed across the width of the slot. The highest normal forces were 1.53 N for the 0.018" archwire, 4.85 N for the 0.020 x 0.020" archwire and 8.18 N for the 0.019 x 0.025" archwire. Passive selfligating brackets presented less frictional resistance than conventional and active selfligating brackets. Regardless of bracket type, greater contact area between the slot and the archwire and the spring clip increased frictional resistance.

El objetivo de este estudio fue comparar la resistencia friccional entre brackets convencionales, de autoligado pasivo y activo por medio del método de elementos finitos (MEF). Se realizaron setenta y nueve (79) deslizamientos combinando brackets convencionales de primer bicúspide superior con arcos de acero de 0,018" y ligadura metálica de 0,010" en una máquina INSTRON 3345, obteniendo el promedio de la resistencia estática máxima (REM). Este valor fue comparado con la resistencia friccional obtenida por simulación de un deslizamiento de la misma combinación por medio de MEF previo diseño asistido por computador (CAD) del bracket convencional. Una vez se validó MEF, se realizaron diseños CAD de los brackets (convencional, autoligado activo y pasivo de primer bicúspide superior derecho) y cálculos de sus propiedades. Se realizó una comparación entre brackets convencionales, brackets de autoligado activo y pasivo con diferentes aleaciones y secciones cruzadas de alambre 0.018", 0.019" x 0.025" y 0.020" x 0.020". Los brackets de autoligado pasivo mostraron la menor REM, seguidos de los brackets convencionales y finalmente los brackets de autoligado activo. En los brackets convencionales, el arco de 0,018" produjo un patrón lineal de stress en el fondo de la ranura, con su máxima concentración en el centro. Por el contrario, los arcos de 0.020" x 0.020" y 0.019 x 0.025" tuvieron una distribución de esfuerzos a través del ancho de la ranura. La mayor fuerza normal en los brackets convencionales fue para el arco 0.019"x 0.025" (8.18N), seguido por el arco 0.020 x 0.020" (4.85N) y finalmente el arco 0.018" (1.53N). Los brackets de autoligado pasivo presentaron menos resistencia friccional que los brackets convencionales y autoligado activo respectivamente. Independiente del tipo de bracket, una mayor área de contacto entre la ranura del bracket y el arco, y el spring clip aumentaron la resistencia friccional.

A Multi-techniques Approach to assess reprocessing of Single-use electrosurgical pencils.

Reprocessing and reuse of single-use electrosurgical pencils (EPs) is a diffused practice in countries with limited access to healthcare subvention system and in developing countries. However, safety and efficacy issues are associated to this practice, requiring specific methods for checking the reprocessed device before clinical re-use. This study aimed at defining a set of testing methods for assessing thermal and surface characteristics of reprocessed single-use EPs and evaluating the suitability of these techniques for revealing modifications between brand new and reprocessed single-use EPs. We reported a multi-technique approach based on optical and electron microscopy, X-rays spectroscopy and thermal analysis. The assessment of a total of 30 variables of interest on both brand new and reprocessed devices, allowed to identify the most informative ones. Seven of the evaluated variables were found to differentiate the reprocessed device from the new ones in a significant way. The presented methods deserve potential for tracking modifications during the device lifecycle.

Comparison of frictional resistance among conventional active and passive solf-ligating brackets with different combinations of arch wires: a finite element study

The aim of this study was to compare frictional resistance among conventional, passive and active selfligating brackets using Finite Elements Analysis (FEA). Seventynine (79) slide tests were performed by combining an upper first bicuspid conventional bracket, 0.018” stainless steel wires and 0.010” ligature by means of an INSTRON 3345 load system to obtain average maximum static frictional resistance (MSFR). This value was compared to the FR (frictional resistance) obtained by simulation of a slide of the same combination by FEA following conventional bracket modeling by means of Computer Aided Design (CAD). Once the FEA was validated, bracket CADs were designed (upper right first bicuspid conventional, active and passive selfligating bracket) and bracket properties calculated. MSFR was compared among conventional, active and passive selfligating brackets with different alloys and archwire cross sections such as 0.018”, 0.019” x 0.025”and 0.020” x 0.020”. Passive selfligating brackets had the lowest MSFR, followed by conventional brackets and active selfligating brackets. In conventional brackets, a 0.018” archwire produced a linear pattern of stress with maximum concentration at the center. Conversely, stress in 0.020 x 0.020” and 0.019 x 0.025” archwires was distributed across the width of the slot. The highest normal forces were 1.53 N for the 0.018” archwire, 4.85 N for the 0.020 x 0.020” archwire and 8.18 N for the 0.019 x 0.025” archwire. Passive selfligating brackets presented less frictional resistance than conventional and active selfligating brackets. Regardless of bracket type, greater contact area between the slot and the archwire and the spring clip increased frictional resistance.

El objetivo de este estudio fue comparar la resistencia friccional entre brackets convencionales, de autoligado pasivo y activo por medio del método de elementos finitos (MEF). Se realizaron setenta y nueve (79) deslizamientos combinando brackets convencionales de primer bicúspide superior con arcos de acero de 0,018” y ligadura metálica de 0,010” en una máquina INSTRON 3345, obteniendo el promedio de la resistencia estática máxima (REM). Este valor fue comparado con la resistencia friccional obtenida por simulación de un deslizamiento de la misma combinación por medio de MEF previo diseño asistido por computador (CAD) del bracket convencional. Una vez se validó MEF, se realizaron diseños CAD de los brackets (convencional, autoligado activo y pasivo de primer bicúspide superior derecho) y cálculos de sus propiedades. Se realizó una comparación entre brackets convencionales, brackets de autoligado activo y pasivo con diferentes aleaciones y secciones cruzadas de alambre 0.018”, 0.019” x 0.025” y 0.020” x 0.020”. Los brackets de autoligado pasivo mostraron la menor REM, seguidos de los brackets convencionales y finalmente los brackets de autoligado activo. En los brackets convencionales, el arco de 0,018” produjo un patrón lineal de stress en el fondo de la ranura, con su máxima concentración en el centro. Por el contrario, los arcos de 0.020” x 0.020” y 0.019 x 0.025” tuvieron una distribución de esfuerzos a través del ancho de la ranura. La mayor fuerza normal en los brackets convencionales fue para el arco 0.019”x 0.025” (8.18N), seguido por el arco 0.020 x 0.020” (4.85N) y finalmente el arco 0.018” (1.53N). Los brackets de autoligado pasivo presentaron menos resistencia friccional que los brackets convencionales y autoligado activo respectivamente. Independiente del tipo de bracket, una mayor área de contacto entre la ranura del bracket y el arco, y el spring clip aumentaron la resistencia friccional.

TOPOGRAPHICAL AND STRUCTURAL EVALUATION OF DIATHERMY PENCILS EMPLOYED ON AESTHETIC SURGERY SUBJECTED TO FOUR REPROCESSING CYCLES USING THE EIA/CES "QUALY" APPROACH / EVALUACIÓN TOPOGRÁFICA Y ESTRUCTURAL DE LÁPICES DE DIATERMIA EMPLEADAS EN CIRUGÍA ESTÉTICA, SOMETIDOS A CUATRO CICLOS DE REPROCESADO UTILIZANDO EL ENFOQUE DE EIA/CES "QUALY" / AVALIAÇÃO TOPOGRÁFICA E ESTRUTURAL DE LÁPIS DE DIATERMIA USADOS EM CIRURGIA COSMÉTICA SOFRIDO QUATRO CICLOS DE REPROCESSAMENTO USANDO A ABORDAGEM DE EIA/CES "QUALY"

Diathermy pencils are one of the most employed medical devices around the world, this condition increases its probability to be reprocessing in patients; diathermy pencil has different parts (cord, tip, handgrip, current cables), which are composed of different kind of materials. In order to identify the medical device behavior is necessary to characterize all of those materials in the instrument. An exploration to determinate topographic surface defects and structural movements in each material was performed, with the intention of evaluated the reuse cycles effects on the medical device. The experiment was performing using the EIA/CES "QUALY" approach [1]. The study concludes that four reprocessing cycles induce some changes that are not statistically representative. Surface defects were detected in the cord; also an aggressive superficial waste after four reprocessing cycles in the tip was observed. We do not observe structural changes in the polymeric chain of the cord.

Los lápices diatermia son uno de los dispositivos médicos más empleados en todo el mundo, condición que aumenta su probabilidad de ser reprocesados con pacientes. El lápiz diatermia tiene diferentes partes (cable, punta, empuñadura, cables de corriente), que están compuestas de diferentes tipos de materiales. Con el fin de identificar el comportamiento de dispositivos médicos es necesario caracterizar todos esos materiales en el instrumento. Se efectuó una exploración de los defectos en la superficie topográfica y determinados movimientos estructurales en cada material, con el propósito de evaluar los efectos de los ciclos de reutilización sobre el dispositivo médico. El experimento se realizó mediante el enfoque "QUALY" EIA/CES [1]. El estudio concluye que cuatro ciclos de reprocesado implican algunos cambios que no son estadísticamente representativos. Se detectaron defectos en la superficie del cable; igualmente, se observó un residuo superficial agresivo después de cuatro ciclos de reprocesamiento en la punta. No se observaron cambios estructurales en la cadena polimérica de la cuerda.

Os lápis de diatermia são um dos dispositivos mais utilizados em todo o mundo médico, uma condição que aumenta a sua chance de ser reprocessados com os pacientes. O lápis de diatermia tem diferentes partes (cabo, ponta, aderência, linhas de energia), que são compostas de materiais diferentes. A fim de identificar o comportamento de dispositivos médicos é necessário caracterizar todos tais materiais no instrumento. Uma varredura de defeitos foi realizado na superfície topográfica e certos movimentos estruturais em cada material, com o objetivo de avaliar os efeitos dos ciclos de reutilização no dispositivo médico. O experimento foi realizado utilizando o EIA/CES [1] abordagem "QUALY". O estudo conclui que quatro ciclos de reprocessamento envolvem algumas mudanças que não são estatisticamente representativa. Os defeitos foram detectados na superfície do cabo; do mesmo modo, um resíduo de superfície agressivo foi observada após quatro ciclos na ponta reprocessamento. Não foram observadas alterações estruturais na cadeia do polímero da corda.