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Positive end-expiratory pressure at minimal respiratory elastance represents the best compromise between mechanical stress and lung aeration in oleic acid induced lung injury

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Critical Care 2007年第4期11卷 1-13页

作者： Carvalho, Alysson Roncally S. Jandre, Frederico C. Pino, Alexandre V. Bozza, Fernando A. Salluh, Jorge Rodrigues, Rosana Ascoli, Fabio O. Giannella-Neto, Antonio Biomedical Engineering Program COPPE Federal University of Rio de Janeiro 21941-914 Rio de Janeiro Av. Horácio Macedo Brazil Fundação Oswaldo Cruz Instituto de Pesquisa Clinica Evandro Chagas e Laboratório de Imunofarmacologia IOC 21045-900 Rio de Janeiro Av Brasil 4365 Manguinhos Brazil National Institute of Cancer-1 ICU 20230-130 Rio de Janeiro Praça Cruz Vermelha Brazil Radiodiagnostic Service Clementino Fraga Filho Hospital Federal University of Rio de Janeiro 21-941-913 Rio de Janeiro R Professor Rodolpho Paulo Rocco 255 Brazil

Introduction: Protective ventilatory strategies have been applied to prevent ventilator-induced lung injury in patients with acute lung injury (ALI). However, adjustment of positive end-expiratory pressure (PEEP) to avoid alveolar de-recruitment and hyperinflation remains difficult. An alternative is to set the PEEP based on minimizing respiratory system elastance (Ers) by titrating PEEP. In the present study we evaluate the distribution of lung aeration (assessed using computed tomography scanning) and the behaviour of Ers in a porcine model of ALI, during a descending PEEP titration manoeuvre with a protective low tidal volume. Methods: PEEP titration (from 26 to 0 cmH₂O, with a tidal volume of 6 to 7 ml/kg) was performed, following a recruitment manoeuvre. At each PEEP, helical computed tomography scans of juxta-diaphragmatic parts of the lower lobes were obtained during end-expiratory and end-inspiratory pauses in six piglets with ALI induced by oleic acid. The distribution of the lung compartments (hyperinflated, normally aerated, poorly aerated and non-aerated areas) was determined and the Ers was estimated on a breath-by-breath basis from the equation of motion of the respiratory system using the least-squares method. Results: Progressive reduction in PEEP from 26 cmH₂O to the PEEP at which the minimum Ers was observed improved poorly aerated areas, with a proportional reduction in hyperinflated areas. Also, the distribution of normally aerated areas remained steady over this interval, with no changes in non-aerated areas. The PEEP at which minimal Ers occurred corresponded to the greatest amount of normally aerated areas, with lesser hyperinflated, and poorly and non-aerated areas. Levels of PEEP below that at which minimal Ers was observed increased poorly and non-aerated areas, with concomitant reductions in normally inflated and hyperinflated areas. Conclusion: The PEEP at which minimal Ers occurred, obtained by descending PEEP titra

关键词： Continuous Positive Airway Pressure Acute Lung Injury Recruitment Manoeuvre Peep Level Lung Aeration

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A frequency-compensated coded-excitation pulse to improve axial resolution of ultrasonic system

A frequency-compensated coded-excitation pulse to improve ax...

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2006 IEEE International Ultrasonics Symposium, IUS

作者： Barros, Álvaro Luiz Pereira Machado, João Carlos Da Costa-Félix, Rodrigo Pereira Barretto Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro RJ Brazil Duque de Caxias RJ Brazil

ISBN: (纸本)1424402018

This work presents a method for coded excitation of ultrasound system using a compensated frequency modulation based on the spectral response of the echo from a flat reflector. The method provides an improvement of the overall range resolution of the ultrasound system comprising the pulse generator, impedance matching networks, receive amplifier and transmit/receive transducer. The method was tested in terms of the range resolution for the echo from a flat reflector and with the transducer of the ultrasound system excited with a linear frequency modulated coded excitation and with the proposed compensated frequency modulation coded excitation. The received echo was compressed using the cross-correlation technique and the width of the compressed echo-pulse envelope was around 1.02 and 0.85 μs for linear frequency modulation and compensated frequency modulation coded excitations, respectively. © 2006 IEEE.

关键词： Frequency modulation

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Detection of the Anaerobic Threshold by Surface Electromyography

Detection of the Anaerobic Threshold by Surface Electromyogr...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Roger G. T. Mello Liliam F. Oliveira Jurandir Nadal Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil Biomechanics Laboratory School of Physical Education and Sports Federal University of Rio de Janeiro Brazil

This work aims at presenting a method for automatic detection of the anaerobic thresholds by surface electromyography (RMS-slope) and compare with respective values identified by the analysis of ventilatory gas exchange. Thirteen healthy adults were submitted to a single maximal oxygen uptake test, being monitored the ventilatory parameters V O2 , V CO2 , and V E , and the surface EMG (SEMG) of the right vastus lateralis muscle. Each cycle of myoelectric activity was automatically detected and the time series of the mean RMS values of these cycles used for determining the SEMG threshold (SEMG-T) by linear regression. The method was successful to determine SEMG-T for all subjects, with consistent results when compared to respective anaerobic thresholds visually estimated in the ventilatory equivalent V E /VO 2

关键词： Electromyography Blood Production Linear regression Frequency estimation Condition monitoring Protocols Muscles Testing Physiology

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P2D-9 A Frequency-Compensated Coded-Excitation Pulse to Improve Axial Resolution of Ultrasonic System

P2D-9 A Frequency-Compensated Coded-Excitation Pulse to Impr...

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IEEE Symposium (IUS) Ultrasonics

作者： R. P. B. da Costa-Felix J. C. Machado A. L. P. Barros Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil Laboratory of Ultrasound National Institute of Metrology Standardization and Industrial Quality Rio de Janeiro Brazil

This work presents a method for coded excitation of ultrasound system using a compensated frequency modulation based on the spectral response of the echo from a flat reflector. The method provides an improvement of the overall range resolution of the ultrasound system comprising the pulse generator, impedance matching networks, receive amplifier and transmit/receive transducer. The method was tested in terms of the range resolution for the echo from a flat reflector and with the transducer of the ultrasound system excited with a linear frequency modulated coded excitation and with the proposed compensated frequency modulation coded excitation. The received echo was compressed using the cross-correlation technique and the width of the compressed echo-pulse envelope was around 1.02 and 0.85 mus for linear frequency modulation and compensated frequency modulation coded excitations, respectively

关键词： Ultrasonic imaging Pulse amplifiers Bandwidth Frequency modulation Ultrasonic transducers Pulse modulation Pulse generation Chirp modulation Impedance matching Frequency response

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P1G-9 Stepped Sine Versus Coded Pulse As Excitation Signals for Ultrasonic Transducer Calibration in a Non-Linear Propagation Field

P1G-9 Stepped Sine Versus Coded Pulse As Excitation Signals ...

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IEEE Symposium (IUS) Ultrasonics

作者： R. P. B. da Costa-Felix J. C. Machado Lab. of Ultrasound Nat. Inst. of Metrol. Stand. & Ind. Quality Duque de Caxias Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Brazil

Secondary calibration of a 2.25 MHz center frequency, 25.4 mm of diameter transducer was performed using two different excitation signals: chirp-coded pulse and a set of pure-tone busts. For some frequencies, measurements were performed in the near and/or distorted field. Chirp-coded excitation was more robust than pure-tone burst, resulting in better measurement with respect to distortion and diffraction occurrence

关键词： Ultrasonic transducers Calibration Chirp Distortion measurement Nonlinear distortion Frequency measurement Ultrasonic variables measurement Performance evaluation Robustness Diffraction

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Classification of breast tumours on ultrasound images using morphometric parameters

Classification of breast tumours on ultrasound images using ...

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IEEE International Symposium on Intelligent Signal Processing

作者： A.V. Alvarenga W.C.A. Pereira A.F.C. Infantosi C.M. de Azevedo Biomedical Engineering Program/COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil Rio de Janeiro Brazil

This work aims to assess the potentiality of morphometric parameters in separating breast tumour, on ultrasonic images, as malign or benign. Parameters were calculated over normalised radial length and convex polygons from 152 segmented tumour images. Linear discriminant analysis was applied and parameters performance assessed (accuracy, sensitivity and specificity). The best parameter performances for individual parameters were the normalised residual mean square value and the circularity. Taking these last two and the roughness the best separation performance was obtained: specificity (90.4%) and sensitivity (88.0%). These three parameters were also applied to a multilayer perceptron network using GA-backpropagation hybrid training. The initial results pointed out that hybrid GA-backpropagation training was capable to produce similar high performance both to training (accuracy = 90.3%, sensitivity = 90.0% and specificity = 90.9%) and test (accuracy, sensitivity and specificity equal to 90.0%) procedures. Besides, the performances obtained with two training sets of distinct sizes (30% and 50% of all samples) were slightly different.

关键词： Breast tumors Ultrasonic imaging Breast cancer Artificial neural networks Sensitivity and specificity Multilayer perceptrons Genetic algorithms Mammography Biopsy Image databases

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The ultrasonic attenuation coefficient for human blood plasma in the frequency range of 7-90 MHz

The ultrasonic attenuation coefficient for human blood plasm...

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2004 IEEE Ultrasonics Symposium

作者： Filho, M. M. Calor Machado, J.C. PETROBRAS Rio de Janeiro RJ 21945-900 Brazil Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro RJ 21945-970 Brazil

ISBN: (纸本)0780384121

This work presents experimental results of the ultrasound attenuation coefficient of human blood plasma in the frequency range of 7-90 MHz. Measurements were done with a sample of 450 μL of plasma immersed in a water bath with the temperature controlled at 36.5°C. The results follow the power law frequency dependence with an exponent of 1.43, compatible with the literature results for low frequency. Also, the results indicate a relaxation mechanism in the vicinity of 10 MHz. © 2004 IEEE.

关键词： Ultrasonics

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Accessibility of selected hospitals and medical procedures by means of aerial and transit network-based measures

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Health Services Management Research 2003年第2期16卷 136-140页

作者： Costa, L.S. Nassi, C.D. Pinheiro, R.S. Almeida, Renan Moritz Varnier R. Biomedical Engineering Program COPPE Federal University of Rio de Janeiro Rio de Janeiro 21945-970 Brazil Transportation Program COPPE Federal University of Rio de Janeiro Rio de Janeiro 21945-970 Brazil NESC Medical School Federal University of Rio de Janeiro Rio de Janeiro 21945-970 Brazil

Objective: This report investigates the use of linear and travelled route (transit network-based) distances in estimating the accessibility of hospitals to patients, for some selected hospital admission diagnostics. Methods: For patients admitted to 14 public hospitals in Rio de Janeiro City, during 1996, under the ICD-9 headings 'Complications of Pregnancy, Childbirth and the Puerperium' and.'Disorders of the Circulatory System', average distances between the patient's district of residence and hospital of admission were calculated (both as Euclidean and as network-based distances). Data were obtained from the country's public health data processing agency. Geographic co-ordinates were obtained for districts of residence from the postal codes of the patients' residences. Distances were estimated with the TransCAD Geographical Information System, based on a map of the city transit network. There were 8654 patients admitted under the 'Complications of Pregnancy' heading and 3439 under 'Disorders of Circulatory System'. Results: Variations of up to a factor of 5.3, and up to 34km, could be identified between linear and network estimates. Conclusion: While recognizing that network estimates have advantages, the literature on accessibility frequently argues that aerial estimates are a good approximation for those. The present results show that this is not necessarily the case.

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Time-Frequency Mapping of the Magnitude Squared-Coherence for Intra-QRS Potentials Detection

Time-Frequency Mapping of the Magnitude Squared-Coherence fo...

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A New Beginning for Human Health: Proceedings of the 25th Annual International Conference of the IEEE engineering in Medicine and Biology Society, EMBS 2003

作者： Barbosa, P.R.B. Bernardino Jr., L.C. Barbosa-Filho, J. Cordovil, I. Nadal, J. Biomed. Engineering Program - COPPE Federal University of Rio de Janeiro Rio de Janeiro Brazil Gama Filho University Rio de Janeiro Brazil National Institute of Cardiology Rio de Janeiro Brazil Biomedical Engineering Program-COPPE Federal University of Rio de Janeiro P.O. Box 68510 21945-970 - Rio de Janeiro - RJ Brazil

Intra-QRS potentials detected in the presence of heart disease represents unstable electrical conduction in damaged myocardium, probably due to dispersion in propagation time-constants. A one-dimensional linear model of continuous velocity waveform transmission is proposed, and a time-frequency magnitude squared-coherence (MSC) mapping of the ventricular activation (VA) of patients with ventricular tachycardia (VT) and normal volunteers was studied. Normal subjects shows high MSC estimates, mainly at the beginning and end of VA. Reduction of MSC estimate throughout VA was observed in VT, which reflects variation in the content of successive spectral estimates. This finding is indicative of fluctuation in propagation velocity of the ventricular activation in damaged myocardium.

关键词： Cardiology

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Time-frequency mapping of the magnitude squared-coherence for intra-QRS potentials detection

Time-frequency mapping of the magnitude squared-coherence fo...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： P.R.B. Barbosa L.C. Bernardino J. Barbosa-Filho I. Cordovil J. Nadal Biomedical Engineering Program-COPPE Federal University of Rio de Janeiro Brazil Gama Filho University Rio de Janeiro Brazil

关键词： Time frequency analysis Myocardium Electrocardiography Surface waves biomedical engineering Cardiology Cardiac disease Fluctuations Filtering Frequency domain analysis

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