149 research outputs found
Sensitivity of Modern Lighting Technologies to Rapid Voltage Changes
Rapid Voltage Changes (RVCs) are one of the Power Quality disturbances that are recently receiving a lot of attention from the point of view of international standards. However, although they can cause or contribute to flicker, IEC 61000-4-15 only addresses periodic amplitude fluctuations and more effort is needed to regulate the occurrence of RVCs, according to their effect on flicker perceptibility. Alongside, flicker perception is challenged by the integration of modern lighting technology, whose response is different from the traditional incandescent lamp. This paper studies the connection between the increasing importance of RVCs and the evolution of illumination technologies. Sensitivity of modern lighting technologies to RVCs is studied by measuring flicker with a high precision light flickermeter. A large set of modern lamps is tested and the relationship between RVCs parameters and flicker perceptibility is analyzed
Metodología de selección de especies de arbolado para el sombreado urbano en la parte oriental de la cornisa Cantábrica
The mitigation of the Urban Heat Island is one of the biggest future challenges in cities due to climate change. One of the methods to achieve the cooling of urban spaces is the attenuation of solar radiation provided by the trees. In the present article, a methodology of selection of arboreal species is proposed for the improvement of thermal comfort in urbanized areas of the eastern part of the Cantabrian coast. Starting from a pre-selection of native species, a classification of various species suitable for shading is obtained, describing its main characteristics and its possible use scope according to the typology of urban space.La mitigación del efecto Isla de Calor es uno de los mayores retos del futuro en las ciudades debido al cambio climático. Uno de los métodos para conseguir el enfriamiento de los espacios urbanos es la atenuación de radiación solar proporcionada por el arbolado. En el presente artículo se plantea una metodología de selección de especies arbóreas para la mejora del confort térmico en zonas urbanizadas de la parte oriental de la cornisa cantábrica. Partiendo de una preselección de especies autóctonas, se obtiene una clasificación de diversas especies aptas para el sombreado describiéndose sus principales características y su posible ámbito de utilización en función de la tipología de espacio urbano
Efecto de la localización del electrodo ventricular izquierdo sobre los parámetros ecocardiográficos de asincronía en pacientes sometidos a terapia de resincronización cardíaca
Introduction and objectives. Cardiac resynchronization
therapy has been shown to be an option in the treatment
of patients with congestive heart failure. The current
indication for this treatment is based on clinical and electrocardiographic
criteria, although echocardiography has
also been shown to be a useful tool for the diagnosis of
ventricular dyssynchrony. The aim of this study was to assess
left ventricular dyssynchrony by echocardiography
and to evaluate the effect of the stimulation site on the
magnitude of resynchronization.
Patients and method. We studied 25 patients with biventricular
stimulation (left ventricular lead located in a lateral
position in 13 patients, and in an anterior position in
12). A complete echo-Doppler evaluation, including left
ventricular ejection fraction, ventricular diameters and parameters
of inter- and intraventricular dyssynchrony, was
performed before implantation and 3 months after the
procedure, with the device connected and disconnected.
Results. Left ventricular ejection fraction increased significantly
from 23.7 (6.5) to 27.8 (5.5) (P=.007) at 3
months. In the group as a whole, biventricular pacing was
associated with a significant decrease in all intraventricular
dyssynchrony parameters (septal-to-lateral wall motion
delay and septal-to-posterior wall motion delay). This decrease
in septal-to-posterior wall motion delay and septalto-
lateral wall motion delay was significantly greater in patients
with the electrode implanted in the lateral position
(58.1 ms vs 118 ms; P=.02) than with the lead in the anterior
position (39.5 ms vs 86.5 ms; P=.04). Three patients,
all with the electrode in an anterior location, were considered
non-responders.
Conclusions. Left lateral free wall stimulation provided
significantly better intraventricular resynchronization compared
to stimulation at an anterior site. Echocardiography
is a useful tool to evaluate changes in intra- and interventricular
synchrony related to the pacing site
Tratamiento de la insuficiencia cardíaca avanzada mediante estimulación biventricular. Experiencia inicial en una serie de 22 casos consecutivos
Recent data suggest that biventricular pacing may play
an important role in treating advanced heart failure in the presence of a
significant interventricular and/or intraventricular conduction disorder by
correcting cardiac dysynchrony. In this article, we review the initial technical
and clinical experience with cardiac resynchronization therapy in an
electrophysiology laboratory. METHODS: The first 22 consecutive patients with
severe congestive heart failure, ejection fraction < 0.35, NYHA functional class
III or IV, and QRS duration > 120 ms who were implanted biventricular pacemakers
were studied. Clinical, electrocardiographic, and echocardiographic evaluations
were made before and three months after pacemaker implantation. Acute functional
capacity testing with peak oxygen uptake was measured during biventricular pacing
and during intrinsic rhythm or right ventricular pacing three months after the
implantation procedure. RESULTS: The success rate of pacemaker implantation was
95%. Pre-discharge left ventricular pacing was achieved in 91%, with an average
pacing threshold of 1.53 (1.04) volts. NYHA functional class improved (p = 0.039)
from 3.4 (0.7) to 2.3 (0.78). The rate of hospitalization for heart failure
decreased from an average of 3.12 (0.58) three months before the procedure to
1.38 (0.34) three months after the procedure. Peak oxygen uptake was
significantly greater (p = 0.028) during biventricular pacing: 14.89 (2.1)
ml/min/kg, than during intrinsic rhythm or right ventricular pacing: 12.65 (2.3)
ml/min/kg. CONCLUSIONS: Cardiac resynchronization therapy can be performed safely
and with a high success rate in the electrophysiology laboratory. Biventricular
pacing seems to improve the symptoms of congestive heart failure in patients with
evidence of atrioventricular and/or interventricular/intraventricular
dysynchrony. An acute benefit in peak oxygen uptake was associated with
biventricular pacing after the implantation procedure
Síndrome CLIPPERS. A propósito de un caso
Presentamos el caso de un varón de 44 años, con antecedentes personales de linfohistiocitosis hemofagocítica primaria
(portador homocigótico de mutación Ala91Val), resuelta tras
esplenectomía. Presenta un cuadro de inicio brusco y curso
progresivo, de 2 meses de evolución, de sensación de adormecimiento y hormigueo en ambas plantas de los pies,
rigidez en las piernas que se desencadena con la actividad
física y sensación de inestabilidad. Además, desde hace 48 h,
asocia adormecimiento y hormigueo de ambas palmas. Niega
antecedentes epidemiológicos de interés
Utilidad de la infusión de adenosin trifosfato (ATP) en el diagnóstico de los pacientes con síncope de origen desconocido
El síncope es una patología frecuente en los servicios de Urgencias que se acompaña de un alto índice de recurrencias. A pesar de las pruebas utilizadas en su estudio, en un alto porcentaje de pacientes no se puede filiar la etiología. Esta revisión analiza el fundamento, la utilidad y las implicaciones terapéuticas del test de infusión de ATP, recientemente incorporado en el estudio del síncope de origen desconocido.Syncope is a common clinical problem in the emergency room. Many patients have recurrences of syncope at follow up. Although many tests have been used for the evaluation of syncope, in some cases it is not possible to find the aetiology. In this paper we analyse the basis, utility and therapeutic implications of ATP test in the diagnosis of syncope of unknown origin
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