Kinetic Monte Carlo simulation analysis of the conductance drift in Multilevel HfO2-based RRAM devices.

The drift characteristics of valence change memory (VCM) devices have been analyzed through both experimental analysis and 3D kinetic Monte Carlo (kMC) simulations. By simulating six distinct low-resistance states (LRS) over a 24-hour period at room temperature, we aim to assess the device temporal stability and retention. Our results demonstrate the feasibility of multi-level operation and reveal insights into the conductive filament (CF) dynamics. The cumulative distribution functions (CDFs) of read-out currents measured at different time intervals provide a comprehensive view of the device performance for the different conductance levels. These findings not only enhance the understanding of VCM device switching behaviour but also allow the development of strategies for improving retention, thereby advancing the development of reliable nonvolatile resistive switching memory technologies.

Variability in HfO2-based memristors described with a new bidimensional statistical technique.

A new statistical analysis is presented to assess cycle-to-cycle variability in resistive memories. This method employs two-dimensional (2D) distributions of parameters to analyse both set and reset voltages and currents, coupled with a 2D coefficient of variation (CV). This 2D methodology significantly enhances the analysis, providing a more thorough and comprehensive understanding of the data compared to conventional one-dimensional methods. Resistive switching (RS) data from two different technologies based on hafnium oxide are used in the variability study. The 2D CV allows a more compact assessment of technology suitability for applications such as non-volatile memories, neuromorphic computing and random number generation circuits.

3D simulation of conductive nanofilaments in multilayer h-BN memristors via a circuit breaker approach.

A 3D simulation of conductive nanofilaments (CNFs) in multilayer hexagonal-BN memristors is performed. To do so, a simulation tool based on circuit breakers is developed including for the first time a 3D resistive network. The circuit breakers employed can be modeled with two, three and four resistance states; in addition, a series resistance and a module to account for quantum effects, by means of the quantum point contact model, are also included. Finally, to describe real dielectric situations, regions with a high defect density are modeled with a great variety of geometrical shapes to consider their influence in the resistive switching (RS) process. The simulator has been tuned with measurements of h-BN memristive devices, fabricated with chemical-vapour-deposition grown h-BN layers, which were electrically and physically characterized. We show the formation of CNFs that produce filamentary charge conduction in our devices. Moreover, the simulation tool is employed to describe partial filament rupture in reset processes and show the low dependence of the set voltage on the device area, which is seen experimentally.

Twenty-first Century Trends in the Global Epidemiology of Pediatric-Onset Inflammatory Bowel Disease: Systematic Review.

BACKGROUND & AIMS: The incidence of inflammatory bowel disease (IBD) is increasing internationally, particularly in nations with historically low rates. Previous reports of the epidemiology of pediatric-onset IBD identified a paucity of data. We systematically reviewed the global trends in incidence and prevalence of IBD diagnosed in individuals <21 years old over the first 2 decades of the 21st century. METHODS: We systematically reviewed studies indexed in MEDLINE, EMBASE, Airiti Library, and SciELO from January 2010 to February 2020 to identify population-based studies reporting the incidence and/or prevalence of IBD, Crohn's disease, ulcerative colitis, and/or IBD-unclassified. Data from studies published before 2000 were derived from a previously published systematic review. We described the geographic distribution and trends in children of all ages and limiting to very early onset (VEO) IBD. RESULTS: A total of 131 studies from 48 countries were included. The incidence and prevalence of pediatric-onset IBD is highest in Northern Europe and North America and lowest in Southern Europe, Asia, and the Middle East. Among studies evaluating trends over time, most (31 of 37, 84%) studies reported significant increases in incidence and all (7 of 7) reported significant increases in prevalence. Data on the incidence and prevalence of VEO-IBD are limited to countries with historically high rates of IBD. Time trends in the incidence of VEO-IBD were visually heterogeneous. CONCLUSIONS: Rates of pediatric-onset IBD continue to rise around the world and data are emerging from regions where it was not previously reported; however, there remains a paucity of data on VEO-IBD and on pediatric IBD from developing and recently developed countries.

Intra-articular human deciduous dental pulp stem cell administration vs. pharmacological therapy in experimental osteoarthritis rat model.

OBJECTIVE: The aim of the present study was to compare the molecular and morphological effects of diacerein and glucosamine-chondroitin drug treatment and intra-articular injection therapy of human deciduous dental pulp stem cells (hDPSCs) in a rat knee model of induced osteoarthritis (OA). MATERIALS AND METHODS: Thirty-six adult male rats were randomly separated into six groups: Control group (without induction of OA), osteoarthritis group 60 (induction of OA, saline gavage started on day 14 and performed for 60 days, followed by euthanasia), osteoarthritis group (induction of OA and euthanasia after 14 days), diacerein group, glucosamine-chondroitin group, and mesenchymal stem cell group. The drug-treated groups were gavaged with 50 mg/kg of diacerein and 400/500 mg/kg of glucosamine-chondroitin starting on dat 14 for 60 days. The cell therapy-treated group received an intra-articular single dose of 8 × 105 hDPSCs on day 14, and euthanasia was performed after 60 days. Lateral femoral condyles were collected and prepared for immunohistochemistry and light microscopy procedures. RESULTS: The morphological features and immunoexpression of SOX-5, IHH, MMP-8, MMP-13, and Type II collagen were statistically analysed. Our data suggest that hDPSC therapy contributes more actively and effectively in the structural reorganization of lateral femoral condyles. In contrast, the glucosamine-chondroitin sulphate treatment was more effective in inflammatory control, while diacerein showed better results associated with the maintenance of the primordial cartilage. CONCLUSIONS: The positive therapeutic effect of daily administered conventional drugs can be confirmed in a rat model of OA. However, one single dose of locally administered hDPSCs provides significant improvement in tissue regeneration in an OA model.

Reproductive Behavior of Copitarsia uncilata (Lepidoptera: Noctuidae).

Copitarsia sp. (Hampson) (Lepidoptera: Noctuidae: Cuculliinae) is a quarantine pest in different countries and affects diverse crops of economic importance in South America. The development of ethological control strategies is an important issue that requires knowing the reproductive behavior of the species involved. Therefore, the aim of this study was to establish the reproductive behavior of Copitarsia uncilata (Burgos & Leiva) and to evaluate the attractiveness of synthetic pheromone compounds under laboratory conditions. Observations of nocturnal reproductive behavior of males and females were performed for 7 days in order to register the courtship, mating, and oviposition time. Once the period of the highest reproductive activity was identified, flight behavior and attraction of virgin males were evaluated in a wind tunnel towards synthetic compounds previously reported as commercial pheromones for Copitarsia species, namely (Z)-tetradec-9-enyl acetate (Z9-14Ac), (Z)-tetradec-9-enol (Z9-14OH), and their mixture (Z9-14Ac + Z9-14OH at 4:1 ratio), in comparison with virgin females and clean air flow. We observed that reproductive behavior occurs during the first third of the scotophase and begins on the second day after adult emergence. Highest proportion of courtship and mating occurs on days 2 and 3 after emergence, and oviposition starts the night immediately after the first mating. Wind tunnel assessments showed that males were highly attracted to calling females compared with the blend of synthetic pheromone compounds, with 89% and 12% of males landing at the source, respectively. Moreover, males also showed a low response to the isolated compounds (Z9-14Ac 14% and Z9-14OH 4%).

Resistive Switching and Charge Transport in Laser-Fabricated Graphene Oxide Memristors: A Time Series and Quantum Point Contact Modeling Approach.

This work investigates the sources of resistive switching (RS) in recently reported laser-fabricated graphene oxide memristors by means of two numerical analysis tools linked to the Time Series Statistical Analysis and the use of the Quantum Point Contact Conduction model. The application of both numerical procedures points to the existence of a filament connecting the electrodes that may be interrupted at a precise point within the conductive path, resulting in resistive switching phenomena. These results support the existing model attributing the memristance of laser-fabricated graphene oxide memristors to the modification of a conductive path stoichiometry inside the graphene oxide.

Reverse Monte Carlo reconstruction algorithm for discrete electron tomography based on HAADF-STEM atom counting.

In this paper, we propose an algorithm to obtain a three-dimensional reconstruction of a single nanoparticle based on the method of atom counting. The location of atoms in three dimensions has been successfully performed using simulations of high-angle-annular-dark-field images from only three zone-axis projections, [110], [310] and [211], for a face-centred cubic particle. These three orientations are typically accessible by low-tilt holders often used in high-performance scanning transmission electron microscopes.

[Urological pathology of lymphatic origin]. / Patología urológica de origen linfático.

OBJECTIVES: Lymphatic disease is a rarely cause of some very unspecific genitourinary manifestations, assuming a diagnostic challenge in most cases. The aim of this paper is to warn about the possible etiology of these urological lymphatic presentations and discuss its management. METHODS: Retrospective review of clinical data in pediatric patients with urological pathology of lymphatic origin between 2008-2014. Three patients, two boys and a girl, were included. The complaints were: redundant prepuce, inguinal scrotal tumor and urinary incontinence. Clinical, diagnosis and treatment protocol is described. RESULTS: The first case is a male with genital lymphedema presented at birth as a redundant prepuce and the subsequent emergence of lower limb lymphedema, treated with compression bandages. The second case, a groin lymphangioma which debuted as a sudden painless inguinal tumor simulating a cord cyst, it was sclerosed and treated with OK- 432. Finally, a preteen who consulted for involuntary leakage of urine, genital lymphedema likely primary cause (lymphodisplasia) or malformation was diagnosed, which improved with two Lipiodol® embolization. CONCLUSIONS: Genitourinary manifestations can be the debut of more complex lymphatic pathology, so it is necessary to consider this cause, uncommon and nonspecific. Its management must be conservative initially by compression bandages, OK-432 or embolization with Lipiodol®.

OBJETIVOS: La patología linfática es infrecuente como causa de manifestaciones genitourinarias inespecíficas, suponiendo un reto diagnóstico en la mayoría de los casos. El objetivo de este trabajo es advertir sobre la posible etiología linfática de estas presentaciones urológicas y discutir su manejo. MATERIAL Y METODOS: Revisión retrospectiva de los datos clínicos de los pacientes pediátricos con patología urológica de origen linfático entre el año 2008-2014. Se incluyeron 3 pacientes, dos niños y una niña. Todos ellos se evaluaron para obtener un diagnóstico fiable. Los motivos de consulta fueron: prepucio redundante, tumoración inguino-escrotal e incontinencia urinaria. Se describe la clínica, el protocolo diagnóstico y el tratamiento de los mismos. CASOS CLINICOS: El primer caso se trata de un lactante varón con un linfedema genital que presentaba un prepucio redundante congénito y la aparición posterior de linfedema en el miembro inferior que es tratado con vendajes compresivos. El siguiente, un linfangioma inguinal que debutó con una tumoración inguinal indolora de aparición súbita simulando un quiste de cordón y tratado mediante esclerosis con OK-432. Por último, una preadolescente que consultó por escapes involuntarios de orina diagnosticada de linfedema genital de probable causa primaria (linfodisplasia) o malformativa que mejoró con dos embolizaciones de Lipiodol®. CONCLUSIONES: Las manifestaciones genitourinarias pueden ser el debut de una patología linfática más compleja, por ello es necesario tener presente esta etiología infrecuente e inespecífica. Su manejo inicialmente debe ser conservador, mediante vendajes compresivos, OK-432 o embolización con Lipiodol®.

Chemical Composition of the Low-Polar Fraction of the Copitarsia uncilata Burgos & Leiva (Lepidoptera: Noctuidae) Eversible Pheromone Gland.

In Colombia, Copitarsia uncilata Burgos & Leiva has been reported as a pest of ornamental flowers. The leafworm causes serious economic losses to farmers because the shipments are intercepted at the detection sites. The identification and subsequent synthesis of the sex pheromone compounds can lead to the use of semiochemicals as an important strategy to complement the pest management. This paper identifies and characterizes the chemical components of the female sexual gland of C. uncilata at three different age stages in order to relate the effect of age on the gland extract composition. Eggs and larvae were collected from commercial crops. The specimens were reared and sexed. Pheromone glands of intact females were excised at (a) 1-2, (b) 3-4, and (c) 5-6 days old. The extracts were analyzed using GC-MS after two extraction time points: 20 min and 8 days. The extracts from the third age stage showed an increase in concentration for 35% of the compounds after 8 days of storage. The relative abundance as a function of the female age showed two trends: an upward trend, where the relative abundances of the compounds increased through the age stages, while some compounds shown a downward trend. Within the first trend, mostly of the compounds were found to be related with infochemicals type structures, where tetradec-9-en-1-yl acetate (within several C-14 long-chain alcohols) is the main one. The 9-14:Ac quadrupled concentration through the ages is possibly related to the increased length of calling period as female moth age.

HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (<20 nm), tips display a curved surface and a significantly larger thickness. As far as a correlative approach aims at analysing the same specimen by both techniques, it is mandatory to explore the limits and advantages imposed by the particular geometry of atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography.

Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission.

In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 10(8) cm(-2)) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required.

Enfoques y fundamentos para un modelo de rehabilitación ambulatoria en personas con lesión cerebral adquirida / Approaches and foundations for a model of outpatient rehabilitation in people whit acquired brain injury

Introducción: Un porcentaje significativo de personas que adquieren una lesión cerebral necesita programas de rehabilitación ambulatoria. En Chile predomina aún un modelo biomédico de rehabilitación, no obstante, las nuevas guías clínicas recomiendan un abordaje interdisciplinario que considere las necesidades del paciente y su familia. Actualmente existe un vacío respecto a cómo operacionalizar intervenciones eficaces que respondan a este paradigma. Objetivo: Encontrar evidencia que permita el desarrollo y evaluación de enfoques en neurorehabilitación ambulatoria de personas con lesión cerebral adquirida y las posibles metodologías de operacionalización de estos. Metodología: Revisión inductiva y conceptual de la literatura. Resultados: En la literatura chilena no existe evidencia empírica ni desarrollos sistemáticos sobre los fundamentos y la efectividad de los programas de rehabilitación ambulatoria para estas personas. En la literatura internacional se destacan tres enfoques: el enfoque holista, el centrado en el cliente y el basado en la planificación de metas. Si bien tales enfoques permiten guiar las acciones de los equipos, la evidencia de su efectividad, en base al criterio de expertos y pequeños estudios longitudinales y de caso único, es aun limitada. Conclusiones: Esencial a la construcción de identidad de un equipo de rehabilitación es determinar los principios y enfoques que sustente su labor. La complejidad y diversidad de los pacientes en la fase ambulatoria requiere que los equipos posean claros fundamentos para guiar la constante toma de decisiones. Es necesaria la evaluación de la eficacia de los programas de rehabilitación ambulatoria en Chile, desarrollando metodologías acordes a la naturaleza multifactorial del fenómeno.

Introduction: A significant percentage of people who acquire a Brain Injury need outpatient rehabilitation programs. In Chile the rehabilitation field is in a transitional stage. Even though the biomedical model is predominant in rehabilitation, the clinical guidelines have begun to recommend an interdisciplinary approach that considers patients needs and their families. Now-a-days, there is a gap on how to operationalize effective interventions responding to this paradigm. Objectives: To find evidence that sustains the development and assessment of outpatient neurorehabilitation approaches of people with brain injury and, to describe the possible operationalization methodologies of these. Methodology: Inductive and conceptual review of literature. Results: In Chilean Literature does not exist empirical evidence nor systematic developments on the foundations and effectiveness of outpatient rehabilitation programs for people with brain injury. International Literature describes three approaches: holistic, client centered, and goal-based. While such approaches can guide the team actions, the evidence of their effectiveness, based on expert criteria and small longitudinal studies and single case studies is still limited. Conclusions: For the development of a rehabilitation team identity, it is essential to determine the principles and approaches that support their work. Due to complexity and diversity of patients in the ambulatory phase, it is crucial that teams have clear foundations to guide the constant decision making. The evaluation of the effectiveness of ambulatory programs in Chile is a necessity; also it is to develop methodologies according to the nature of the phenomenon.

HLA-DRB1*04 and HLA-DQB1*03 association with the atrophic but not with the goitrous form of chronic autoimmune thyroiditis in a Brazilian population.

Autoimmune chronic lymphocytic thyroiditis appears in two forms, goitrous and atrophic. The evidence available is not enough to prove that the goitrous precedes the atrophic form, but immunogenetic analysis suggests that they may be distinct entities. The distribution of HLA class II alleles DRB1* and DQB1* was verified in patients from the region of Campinas, São Paulo, Brazil with both forms of thyroiditis. Ninety-one patients with primary hypothyroidism through autoimmune thyroiditis were classified as goitrous - 54 patients, 42.27 +/- 11.72 years old, having had hypothyroidism for 8.57 +/- 6.63 years - or atrophic - 37 patients, 42.72 +/- 12.01 years old, hypothyroidism for 6.73 +/- 4.07 years. The distribution of class II alleles was determined, DRB1* and DQB1* were genotyped after purifying DNA blood samples using the DNAzol technique, and the low-resolution PCR-SSP system was utilized for determination of generic alleles. Chi-square and Fisher's exact test were utilized to compare the distribution frequency of HLA alleles and the significant p-values were subjected to Bonferroni correction. We have demonstrated that the DRB1*04 allele is associated with autoimmune thyroiditis, and that there are genotypic differences regarding the presentation forms with a strong association between DRB1*04 and DQB1*03 and the atrophic form only.

[Exercise limitation in patients with chronic obstructive pulmonary disease at the altitude of Bogota (2640 m). Breathing pattern and arterial gases at rest and peak exercise]. / Limitación a la tolerancia al ejercicio en pacientes con EPOC a la altura de Bogotá (2.640m). Patrón respiratorio y gasometría arterial en reposo y en ejercicio pico.

OBJECTIVE: To describe the response to exercise of normal subjects and patients with chronic obstructive pulmonary disease (COPD) in Bogota, Colombia (altitude: 2640 m; atmospheric pressure: 560 mm Hg) and compare it with data published on COPD patients at sea level. Healthy people increase their minute ventilation to attenuate hypoxemia (PaCO2: 30 mm Hg; PaO2: 63 mm Hg). MATERIAL AND METHOD: A descriptive study was carried out on healthy subjects and COPD patients. Exercise limitation was determined by an incremental test on a cycle ergometer. RESULTS: The study enrolled 16 healthy subjects and 25 COPD patients (forced expiratory volume in 1 second: 43.3% [SD 13%]). Minute ventilation at rest was greater in COPD patients compared with healthy subjects, it was not adequately sustained during exercise, and there was a reduction in peak oxygen uptake (53.0% [15%]). At peak exercise, inspiratory capacity decreased (-0.62 [0.34] L), the ratio of minute ventilation to maximal voluntary ventilation increased, and severe hypoxemia occurred (PaO2: 49.9 [9.9] mm Hg). There was significant correlation between hypoxemia and the percentage of predicted peak oxygen uptake (r=0.60), leg fatigue (r=-0.62), percentage of predicted peak inspiratory capacity (r=0.61), and the percentage of predicted peak tidal volume (r=0.49). Minute ventilation at rest was shown to be higher, there was a greater reduction in the inspiratory capacity during exercise, and hypoxemia was more severe at rest and during exercise for patients with COPD in Bogota, compared with those at sea level. CONCLUSIONS: Patients with COPD living in Bogota were shown to have lower tolerance to exercise evidenced by ventilatory limitation and severe hypoxemia. Increased minute ventilation at rest, greater reduction in inspiratory capacity, and severity of hypoxemia during exercise were the main differences between COPD in Bogota and at sea level.

[Premature mortality in the early postoperative period of liver transplantation]. / Mortalidad precoz en el postoperatorio inmediato del trasplante hepático.

OBJECTIVES: To analyze the relation between premature death and complications that develop in the early postoperative period after liver transplantation. MATERIAL AND METHODS: Liver transplants performed in adults in our hospital were reviewed retrospectively. Patients were distributed in 2 groups, those who died and those who survived the early recovery period, and the incidences of complications in the two groups were compared using a chi 2 for single variables and logistic regression for multiple variables. RESULTS: In the 827 liver transplants studied, the recipient died in 86 cases, 7 inside the operating room (0.85%) and 79 during recovery (9.63%), for an overall mortality rate of 10.4% for surgery and the immediate postoperative period. Complications that were significantly different with respect to mortality in the multivariant analysis were post-reperfusion syndrome, atrial fibrillation, acute renal failure, and infection. CONCLUSIONS: Only one of the complications was specific to liver transplantation: post-reperfusion syndrome. The others were of the type found in any critically ill patient, an nearly all led to an increase in infections, which is the most common reason for death during surgical recovery.

[Drop-out from out-patient treatment for alcohol dependence: a two-year prospective study]. / Abandono del tratamiento para dependencia alcohólica en medio ambulatorio: estudio prospectivo de dos años.

INTRODUCTION: Treatment compliance in alcohol-dependent patients seems closely related to abstinence rates, so it could be an outcome measure. The aim of our study was to identify which sociodemographic and clinical characteristics of alcohol-dependent patients are associated to high drop-out rates. METHOD: 165 alcohol-dependent out-patients were assessed by means of a structured questionnaire and followed for two years. RESULTS: It was shown a predictive value for personal history of suicidal intents or affective and anxiety disorders, comorbidity with affective and personality disorders, family history of affective disorders and psychiatric and somatic complications of dependence, and past or present abstinence. DISCUSSION: Implications of these findings and inconsistencies between previous studies and these results are discussed.

Experiencia en trauma renal en niños: Hospital Clínico San Borja Arriarán / Renal trauma experience in children: San Borja Arriarán Clinical Hospital

El tratamiento abdominal se ha convertido en un problema emergente y dentro de éste el órgano más frecuentemente lesionado este riñón. El objetivo de nuestro trabajo fue caracterizar epidemiológicamente y analizar la conducta terapéutica de los traumas renales ingresados a nuestro servicio. Se analizaron retrospectivamente las fichas clínicas de 42 pacientes ingresados por traumatismo abdominal complicado en el Servicio de Urgencia del Hospital San Borja Arriarán entre los años 1984 a 2001. De los pacientes con trauma renal se analizó la información referente a exámenes clínicos e imagenológicos, su clasificación, su tratamiento y complicaciones. De los 42 traumas abdominales hubo 13 casos con compromiso renal, los exámenes realizados fueron análisis de orina en todos los casos, ecografía renal en 9,TAC en 6 UIV en 5 angiografía renal en un caso. La frecuencia de las lesiones fue: 5 Grado 2, 1 Grado 3, 5 Grado 4, 1 Grado 5. La relación hombre mujer fue de 3,6: 1 con un promedio de edad de 9 años 6 meses, los mecanismos de lesión más frecuentes fueron caídas de altura, golpe directo y atropello (con 4 casos cada uno), el manejo fue expectante en 10 casos y de resolución quirúrgica de urgencia en 3. En 3 pacientes en que se mantuvo conducta expectante debió realizarse una cirugía electiva por complicaciones. Se realizaron 2 nefrectomías y una heminefrectomía. El promedio de estadía hospitalaria fue de 15 días, siendo 31 para los pacientes con cirugía y de 6 días para los que no quirúrgicos. Nuestro trabajo concuerda con la literatura en que el riñón más frecuentemente lesionado en los traumas abdominales. Existe una clara diferencia en cuanto al sexo, siendo el grupo más afectado los hombres entre 7 a 12 años. Dentro de los exámenes realizados, la ecografía es uno de los más solicitados. Se observa a través de los años analizados una tendencia hacia un manejo conservador para las lesiones renales.

Expiratory muscle endurance in middle-aged healthy subjects.

To evaluate expiratory muscle endurance in middle-aged healthy subjects using incremental as well as constant expiratory loads, 14 healthy volunteers (51 +/- 16 years) were submitted to a specific endurance test, which was performed breathing against a threshold valve, and was divided into two parts. In part I, the load was progressively increased (50 g each 2 min) until task failure occurred. The mean mouth pressure generated against the highest load held for at least 60 sec was defined as the maximal expiratory sustainable pressure (Pth(max)). In part II, each subject breathed against a constant submaximal expiratory load (80% Pth(max)) until task failure occurred (expiratory endurance time or Tth(80)). Both parts of the test were repeated 24-48 h later. Progressive expiratory loading induced a linear increase in mouth expiratory pressure and the Pth(max) obtained was 141 +/- 43 cm H(2)O, representing 74 +/- 28% of the maximal expiratory pressure (PE(max)). Under constant loads, the Tth(80) was 17 +/- 9 min. At the end-point of both parts, the tension time index for expiratory muscles was dramatically increased (>0.25), and both EMG central frequency and PE(max) were decreased with no changes in maximal inspiratory pressure or inspiratory capacity. Extreme dyspnea was present in most of the subjects but no complications were observed. The endurance of expiratory muscles can be easily assessed in healthy subjects using this method, which has acceptable reproducibility and tolerance.