Análisis numérico de una prótesis endobronquial utilizada para el tratamiento de cáncer pulmonar / Numerical analysis of intrabronchial prosthesis used for the treatment of lung cancer

En México, la mortalidad debido a enfermedades bronco-respiratorias se ubica en el sexto lugar según datos estadísticos dados por el Instituto Nacional de Enfermedades Respiratorias (INER). Esto genera la necesidad de incrementar la eficiencia en la aplicación de los tratamientos usados para este tipo de patología. Algunos de los métodos utilizados con mayor frecuencia para el tratamiento de estas dolencias hacen uso de micro dispositivos, también conocidos como válvulas endobronquiales. Este es un sistema alternativo que evita cirugías invasivas y logra prolongar e incrementar la calidad de vida de los pacientes. En este trabajo se presenta el análisis del desempeño de la válvula IBV®. Para el desarrollo del estudio numérico se determinaron las dimensiones y propiedades mecánicas del modelo a partir de catálogos del fabricante. Se desarrolló un modelo para el cual se consideraron las propiedades del Nitinol® y Silastic®. Asimismo, se propusieron dos condiciones de operación para la válvula, una anclada en el bronquio y la otra en la condición en la que se encuentra plegada dentro del broncoscopio. Se utilizó el Método del elemento finito (MEF) para simular las condiciones de trabajo de la válvula. Los resultados encontrados muestran el funcionamiento estructural y el nivel de los esfuerzos generados en el implante durante el ciclo de respiración forzada del individuo. Además, se proporcionan las bases para generar un nuevo dispositivo que pueda emular el funcionamiento de este tipo de implantes y aumente la eficiencia del tratamiento de dicha patología.

In Mexico, the mortality rate due to bronchial respiratory sickness is placed in the sixth position, according to statistics from the National Institute of Breathing Sickness (INER), so it is convenient to increment the efficiency of treatments for those pathologies. The intrabronchial valve is a recommended alternative method; being it main objective to avoid invasive surgery and increase the time and quality of patient´s life. Within this work a biomechanical analysis of an IBV® valve is carried out. Regarding the numerical analysis, the dimensions and mechanical properties of the valve were proposed based on catalogues published by the manufacturer as more reliable information was not available in the open literature. As a result, a new model was developed in which both materials Nitinol® and Silastic® are considered as the main valve materials. The proposed working conditions assume that the valve is implanted in folded form at the bronchus and then anchored when it is unfolded. Finite Element Method (FEM) was used to simulate the proposed working conditions. Results obtained show the structural performance and the level of stress generated in the implant during the breathing cycle. In addition, it provides the knowledge to generate a new device that could emulate the performance of these implants and develop a more efficient treatment this disease.

Viability and enzymatic activity of cryopreserved porcine heart valve

Fibroblast viability of a natural tissue valve for replacing a defective heart valve through allograft or xenograft has been suggested to affect its clinical durability. In this study, the cell viability and enzymatic activity of porcine heart valve leaflets were examined in regard to concerning to the preservation process [variable warm ischemic time (WIT), cold ischemic time (CIT), and cryopreservation]. Porcine heart enblocs were obtained and valve dissection was performed after 2, 12, 24, or 36 hours, in respective groups A, B, C, and D, as WIT. Each group was stored for 24 hours as CIT and cryopreserved. Leaflets were dissected from a valved conduit after each process, and cell viability and enzymatic activity in the leaflet were investigated using trypan blue staining and API ZYM kits. WIT extension significantly decreased fibroblast viability (p < 0.05, 92.25 +/- 2.7% at 2 hours, 84.9 +/- 6.7% at 12 hours, 57.0 +/- 10.2% at 24 hours, 55.9 +/- 7.9% at 36 hours), while CIT for 24 hours was also influenced significantly (p < 0.05), whereas cryopreservation demonstrated no effect on cellular viability. In enzyme activity observation, several enzymes related to lipid or nucleotide degradation (esterase, esterase lipase, particularly phosphatase, phosphohydrolase) were remarkably changed following the valve-fabrication process. After 24 hours CIT, these enzymatic activities in groups B, C and D significantly increased, but the activities decreased after cryopreservation. Particularly, both the viability and enzymatic activity showed remarkable changes after CIT in group B (WIT = 12 hours). These results suggest that WIT is more important than CIT in maintaining viability of the valve, and that completing all the cryopreservation process within 12 hours after acquisition is recommended.

Comparação ecodopplercardiográfica da dinâmica valvar entre atletas ciclistas, corredores e futebolistas e indivíduos sedentários / Comparative Doppler Echocardiographic Assesement of Valvar Function in Cyclists, Runners and Soccer Players Athletes, and Sedentary Subjects

PURPOSE--To compare the patterns of valvar dynamics expressed by the mitral prolapse and regurgitation across the valves, between competitive athletes players of distinctive sport modalities, and between these and sedentary control subjects. METHODS--Pulsed and continuous wave non-colour Doppler echocardiographic evaluation of mitral valvular movements and flow patterns across the different valves was comparatively performed in 10 cyclists, 10 runners, 19 football players, and in 17 sedentary nonathletes controls, all males with ages ranging between 16 and 28 years old (p > 0.05). Valvar dynamics was evaluated from the apical two and four-chamber and parasternal short-axis and long-axis views. The proportions of valvar functional patterns in each group were compared using the chi-square test. RESULTS--Similar (p > 0.05) and high frequency of mitral prolapse were detected in the cyclists (30 per cent ), runners (50 per cent ), football players (32 per cent ), and controls (47 per cent ). Mitral, tricuspid and pulmonary regurgitations were very frequent and their proportions similar (p > 0.05) in the cyclists (40 per cent , 80 per cent and 40 per cent , respectively), runners (50 per cent , 70 per cent and 60 per cent ), football players (37 per cent , 58 per cent and 58 per cent ), and controls (41 per cent , 35 per cent and 35 per cent ). No significant difference (p > 0.05) was observed between cyclists (20 per cent ), runners (20 per cent ), football players (16 per cent ), and controls (35 per cent ) for the frequency of mitral prolapse plus regurgitation. Aortic regurgitation was not observed in any athlete or control subject. CONCLUSION--Neither the practice, nor the sport modalities studied appears to influence the prevalence of mitral prolapse and mitral, tricuspid and pulmonary valvar regurgitation. In all likelihood, these manifestations represent physiological variants of valvar dynamic which can be better detected by means of Doppler echocardiography

Objetivo - Comparar os padrões de dinâmica valvar traduzidos pelo prolapso da valva mitral (PVM) e refluxos valvares entre atletas competidores de modalidades esportivas distintas e, entre estes, e indivíduos sedentários. Métodos - A dinâmica valvar foi avaliada pela ecocardiografia com Doppler pulsado e contínuo não colorido, por meio dos cortes apicais de 2 e 4 câmaras e paraesternais longitudinal e transversal, em 10 ciclistas, 10 corredores, 19 futebolistas e em 17 controles sedentários, todos do sexo masculino, com idades entre 16 e 28 anos (p>0,05). As proporções dos padrões funcionais valvares em cada grupo foram comparadas pelo teste do qui-quadrado. Resultados - A freqüência de PVM foi elevada e semelhante (p>0,05) nos ciclistas (30%), corredores (50%), futebolistas (32%) e controles (47%). Regurgitação através das valvas mitral, tricúspide e pulmonar foi achado freqüente e suas proporções não diferiram (p>0,05) entre ciclistas (40%, 80% e 40%, respectivamente), corredores (50%, 70% e 60%), futebolistas (37%, 58% e 58%) e indivíduos controles (41%, 35% e 35%). A freqüência de PVM associado com regurgitação através desta valva, também mostrou-se semelhante (p>0,05) nos ciclistas (20%), corredores (20%), futebolistas (16%) e indivíduos sedentários (35%). Regurgitação aórtica não foi observada em quaisquer dos grupos. Conclusão - Nem a prática regular e nem a modalidade do exercicio físico mantido por ciclistas, corredores e futebolistas, parecem modificar a dinâmica valvar. As elevadas e semelhantes freqüências de PVM e de refluxos valvares encontradas nos diferentes grupos, sugerem que estas manifestações funcionais sejam variantes fisiológicas da dinâmica valvar, melhor identificadas pela ecodopplercardiografia

Padröes ecocardiográficos normais em crianças na cidade do Rio de Janeiro: II - Medidas dos diâmetros, dimensöes, espessuras de estruturas cardíacas e movimentos valvares / Normal echocardiographic patterns in children in the city of Rio de Janeiro: II - Measures of the diameters, dimensions, cardiac structures thickeness and valvar movements

Foram estudadas 127 crianças normais, na faixa etária de 1 a 144 meses, 65 do sexo masculino e 62 do feminino. Todas apresentavam exame físico, eletrocardiograma e radiografia de tórax normais e encontravam-se dentro dos limites normais de peso e altura para a populaçäo brasileira. O ecocardiograma foi realizado de acordo com normas padronizadas internacionalmente e nenhuma medicaçäo sedativa foi utilizada. As medidas realizadas foram: diâmetro da aorta (AO), abertura sistólica da valva aórtica (Ab. V.Ao), dimensöes do átrio esquerdo (AE) e do ventrículo direito (VD), trato de saída do ventrículo direito (TSVD), espessuras diastlica e sistólica do septo e da parede posterior do ventrículo esquerdo (SD, SS, PPVE-d e PPVE-s), amplitude de excursäo D-E (Exc. DE) e velocidade da rampa E-F da valva mitral (EF mit.), depressäo "a" e velocidade da rampa E-F da valva pulmonar (dep. "a" e EF pul.), relaçäo átrio esquerdo/diâmetro da aorta (Rel. AE/AO), relaçäo septo/parede posterior do ventrículo esquerdo (Rel. S/PPVE)