RESUMO
This paper discussed how the bioengineering and medical engineering started in Argentina.
Assuntos
Engenharia Biomédica/educação , Engenharia Biomédica/história , Argentina , História do Século XX , História do Século XXI , HumanosAssuntos
Biologia/história , Eletrofisiologia/história , Magnetismo/história , Biologia/instrumentação , Biologia/métodos , Eletrofisiologia/instrumentação , Eletrofisiologia/métodos , Europa (Continente) , História do Século XVIII , História do Século XIX , História do Século XX , Humanos , Magnetismo/uso terapêutico , Estados UnidosRESUMO
The electromyographic study of the muscles involved in the complex movements of the shoulder, is usually one way to quantifying the static and dynamic joint's behavior. In particular, the deltoid medium EMG produced a phenomenon similar to a hysteresis cycle when its amplitude was plotted as a function of the lateral angular position during a static, step by step, sequential abduction-adduction of the arm. Such a cycle was consistently repeated in 16 subjects (12 males and 4 females). The paired Student t-test, after comparing the mean EMG values of the rectified wave for the same arm opening angle between abduction and adduction, produced a highly significant difference (alpha<0.001) in all subjects. In all likelihood, it manifests the participation of muscles other than the deltoid medium in the overall movement (as for example, the anterior and posterior deltoids), that is, they are collaborating muscles that are different in the opening or lifting of the arm from those involved in its closure or lowering. Thus, it is concluded that a quantifiable and significant deltoid medium EMG difference has been demonstrated when the muscle is either ready to abduction or ready to adduction. The effect is fully reproducible between 0 and 90 degrees of an arm in static position within the scapular plane.
Assuntos
Eletromiografia/métodos , Movimento/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Equilíbrio Postural/fisiologia , Postura/fisiologia , Ombro/fisiologia , Ciclos de Atividade/fisiologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dinâmica não Linear , RotaçãoRESUMO
Muscle fibre conduction velocity is an important measurement in electrophysiology, both in the research laboratory and in clinical practice. It is usually measured by placing electrodes spaced at known distances and estimating the transit time of the action potential. The problem, common to all methods, is the estimation of this time delay. Several measurement procedures, in the time and frequency domains, have been proposed. Time-domain strategies usually require two acquisition channels, whereas some frequency-domain methods can be implemented using a single one. The method described operates in the time domain, making use of the autocorrelation function of the difference signal obtained from two needle electrodes and only one acquisition channel. Experimental results were obtained from the electromyogram of two biceps muscles (two adult male subjects, nine records each) under voluntary contraction, yielding an average of 3.58 m s(-1) (SD=0.04 m s(-1)) and 3.37m s(-1) (SD=0.03 m s(-1)), respectively. Several tests showed that the proposed method works properly with electromyogram records as short as 0.3 s.
Assuntos
Eletromiografia/métodos , Fibras Musculares Esqueléticas/fisiologia , Condução Nervosa , Potenciais de Ação , Adulto , Humanos , Masculino , Processamento de Sinais Assistido por ComputadorRESUMO
Classic impedance microbiology (CIM) is based on the measurement of the impedance components that appear between a pair of electrodes submerged in a cell containing inoculated broth. Either a bipolar or a tetrapolar technique can be applied, requiring about 1 x 10(3) to 3 x 10(7) cells/ml to produce detectable changes in the impedance curves. Theoretical analysis of the electrode-electrolyte interface during bacterial growth is lacking, with no generally accepted measuring standards. Besides, there is considerable disagreement. We separated out the interface and medium components using the frequency variation technique (FVT) and also analyzed the interface reactance-resistance diagram, both before and after bacterial growth. Medium resistance Rm, interface reactance Xi, and interface resistance Ri, were quantified as time functions growth curves, from the complex bipolar impedance seen between two electrodes. We took into account the electrical current density, the temperature and the associated circuitry, also explaining the theoretical and experimental bases that justify the proposed dissecting procedure. It was found that, within the working frequency range, Rm, Ri, and Xi percental growth curves are frequency-independent, i.e., neither Rm(f), nor Xi(f) nor Ri(f) changed their slopes before, during and after bacterial growth. Besides, no alpha-dispersion effect in Rm curves was detected. It is concluded that impedance microbiology could become a fertile area for interdisciplinary knowledge; its development might offer new avenues for basic and applied research.
Assuntos
Impedância Elétrica , Fenômenos Fisiológicos Bacterianos , Eletrofisiologia , Modelos Estatísticos , Fatores de TempoRESUMO
Left ventricular volume calibration based on the conductance catheter depends on the correct determination of the parallel conductance (Gp). Baan's saline manoeuvre procedure leads to Gp by finding the end-systolic (Ges) and end-diastolic (Ged) conductances, for each beat of the dilution curve rising limb. After plotting such values in an xy-system, their linear regression is back-projected to intersect the identity line, so yielding an estimated Gp. The objective is to theoretically analyse all possible lines, Ges = aGed + b (Baan's line) and, based on experimental results, to establish their limitations. This was attained by calculating the regression lines using, first Ged = f1(Ges) and thereafter, Ges = f2(Ged), which led to two values, Gp2 and Gp1, for the parallel conductance. The morphology of the saline curve was also modified to assess its effect on the extrapolation. Multiple dilutions were recorded in eight experimental dogs injecting different concentrations. Each curve was classified according to the maximum change (VAR) reached by the total average conductance. Over 138 manoeuvres, 276 regressions were processed yielding correlations higher than 0.65. Of this total, 92.4% gave positive parallel conductances. The rest produced negative values and, thus, were neglected. If the two (Ged, Ges) statistical relationships were ideal, they should yield Gp = Gp1 = Gp2; however, there were differences which, when Gp1 was studied against Gp2, led to: Gp1 = 0.97 Gp2 + 0.055, with r = 0.9476, and n = 85. The remaining 53 were discarded because either some Gp values were negative, or the correlation of Ges which Ged (or vice versa) was < 0.85, and/or VAR < 15%; the two latter conditions were found necessary for reliable calibration. Baan's line high correlation is not a unique condition to ensure the accuracy and precision of Gp determination because the slope a depends on VAR and, thus, different intersections with the identity line may be obtained. Its recommended that manoeuvres be used with at least eight data points, with VAR > 15% and, finally, with (Ges, Ged) correlation better than 0.85. Theoretical analysis of Baan's line offers a reference frame, which contains only a limited number of practical possibilities.
Assuntos
Volume Cardíaco , Animais , Calibragem , Cardiografia de Impedância , Cães , Ventrículos do Coração , Modelos BiológicosRESUMO
The conductance catheter has gained momentum since its introduction in cardiovascular dynamics back in 1980. However, measuring errors are still blurring its clinical acceptance. The main objective here was to study the effects of the injected saline concentration and temperature on the evaluation of the parallel conductance, Gp, and thus, on the correction volume Vp. That conductance, Gp, and its associated volume, Vp, were computed using 167 saline dilution curves obtained with boluses at different concentrations and temperatures, injected in seven anesthetized closed-chest dogs. The excursion of the total conductance relative to the steady-state value during a saline maneuver showed good correlation with the injected concentration at both studied temperatures. The reference parallel volume (one reference per dog) was defined as the average value obtained with three successive maneuvers, at 6-M concentration and at body temperature; therefore, the method acted as its own reference. The variation of Vp relative to the reference value was clearly dependent on the injected concentration and on its temperature; dispersion was greater at 22 degrees C than at 40 degrees C. The variability would recognize also other causes, such as uncertainty of the extrapolation procedure and the thoracic redistribution of electrical field lines. As conclusion, it is recommended to characterize each maneuver by its concentration and temperature. Body temperature and 6-M concentration appear as the most recommendable combination for the injectate in most animals. Finally, these results intend to characterize the Vp estimation procedure in order to minimize errors. The variability of Vp, in different experimental conditions, demonstrated that both concentration and temperature are additional parameters that may modify the Gp estimate.
Assuntos
Cateterismo Cardíaco/métodos , Volume Cardíaco , Solução Salina Hipertônica/administração & dosagem , Temperatura , Animais , Cateterismo Cardíaco/normas , Cães , Modelos Lineares , Sístole/fisiologiaRESUMO
The impedancimetric method is a technique for the rapid evaluation of milk bacterial content and also of its subproducts. Several authors have made use of culture conductance changes during bacterial growth for quantitative and qualitative assessments of microbial growth. However, interface capacitance curves, Ci, have not been used. In this paper, we quantify bacteria in cow raw milk by following their growth as the above-mentioned capacitance change time course event. With it, bigger growth variations, shorter detection times and a better coefficient of correlation with the plate count method were obtained than those yielded by conductance curves. Calibration was performed by plotting initial known concentrations, IC (CFU/ml), as a function of the time detection theshold (TDT).
Assuntos
Bactérias/crescimento & desenvolvimento , Contagem de Colônia Microbiana/métodos , Condutometria/métodos , Leite/microbiologia , Animais , BovinosRESUMO
An apparatus for the measurement of bacterial growth is described. The instrument applies alternate adequate sequential currents of two different frequencies through a pair of electrodes immersed in a cultured medium. It monitors, detects and quantifies the growth of micro-organisms based on the measurement of the impedance across the two electrodes and, simultaneously, it measures the variation in the medium turbidity. The medium conductivity and the interface electrode impedance changes can be extracted from the measured impedance. The variations in turbidity can be calibrated in absorbance or optical density units. Moreover, all these parameters are also proportional to bacterial proliferation. The computer-controlled apparatus processes and displays the parameters on a monitor showing bulk resistance, electrode impedance and turbidity changes as time course events. The equipment can detect aerobic or anaerobic micro-organisms and permits the operator simultaneously to assess impedance and turbidity, or it can produce each parameter as a separate event. Time growth curves of different micro-organisms are presented in the results.
Assuntos
Bactérias/crescimento & desenvolvimento , Técnicas Bacteriológicas/instrumentação , Impedância Elétrica , Eletrônica Médica , Nefelometria e Turbidimetria/instrumentaçãoRESUMO
Movement of a straight arm centred at the shoulder joint in three successive 90 degrees rotations, each around the respective orthogonal coordinate axis, leads to an apparently unrelated 90 degrees rotation around the longitudinal arm axis. This empirical fact is known as Codman's paradox, after a Bostonian surgeon who first reported it in 1934. However, by means of homogeneous coordinates, it is herein demonstrated that the phenomenon is just a mechanical property mathematically described by the equivalence between the matricial product of three orthogonal rotation matrices applied to a position vector and the matricial product of a single rotation matrix applied to the same vector. The latter rotation matrix corresponds to the middle one in the former group of three. When polar coordinates are used, the demonstration is even simpler, for the total shift vector clearly shows a single net effect on the longitudinal axis rotation. Thus, Codman's paradox is not a paradox. This property improves the muscle dynamics arm knowledge and might find applications in robotics.
Assuntos
Braço/fisiologia , Fenômenos Biomecânicos , Engenharia Biomédica , Eletromiografia , Humanos , Matemática , Modelos Biológicos , RotaçãoRESUMO
After a brief historical overview, the concept of electrical impedance is introduced as a principle of transduction calling attention to the possible mechanisms by which a physiological event may change impedance, i.e., by geometric, resistivity, and/or permittivity changes. Thereafter, since impedance measurements usually require the injection of current, its biological effects are discussed in order to establish the safety criteria. Finally, the elements found in an impedancimetric circuit and their respective nature are presented and described. The particular behavior of the biological impedance and the electrode/electrolyte interface appear immediately as strikingly important. The section ends with a bird's-eye view of the basic circuitry to measure impedance. Each subsection is closed by partial conclusions to underline the relevant concepts.
Assuntos
Impedância Elétrica , Eletrofisiologia/métodos , Animais , Fenômenos Fisiológicos Sanguíneos , Estimulação Elétrica , Eletrodos , Eletrólitos , Hematócrito , Humanos , TemperaturaRESUMO
The measurement of a physiological event caused by a change in dimension, conductivity, or permittivity can be easily carried out by the impedance technique, requiring only the application of two or more electrodes, which are easy to apply. In some cases, the impedance is transformed into its resistive and reactive components, in others the total impedance is measured. In certain cases only a change in impedance, with or without separation into its components, contains enough information to be correlated to the physiological event. Recent measurements of physiological data by impedance techniques have reemphasized the value of the painless and harmless acquisition from human and animal subjects in such diverse domains as manned spacecraft, nutrition, and electrical impedance imaging. This part attempts to present all the numerous experiments performed on humans to estimate changes in volume, orientation, and distribution of fluids and tissues accompanying physiological activity. The main sections concern the respiratory system, the cardiovascular system, the brain, the total body impedance, muscle and skin impedance, and bacteriometry.
Assuntos
Fenômenos Fisiológicos Cardiovasculares , Impedância Elétrica , Eletrofisiologia/métodos , Monitorização Fisiológica/métodos , Diálise Renal , Animais , Líquidos Corporais/fisiologia , Encéfalo/fisiologia , Eletroencefalografia/métodos , Epilepsia , Extremidades/fisiologia , Feminino , Humanos , Lactente , Recém-Nascido , Técnicas Microbiológicas , Modelos Biológicos , Gravidez , Fenômenos Fisiológicos Respiratórios , TomografiaRESUMO
Among the factors involved in the induction, generalization, and reversion of cardiac fibrillation, the amount of tissue is a determinant factor. One question is whether an increase in myocardial mass would or would not require the same electrical threshold. Accordingly, one objective was to determine if ventricular weight (VW) has any effect on the fibrillation thresholds (FTs). A second objective was to find a possible relationship between spontaneous defibrillation (SPDE) and heart weight. Fifty mongrel dogs of both sexes were used, of which 26 were 2- to 10-week-old puppies. The rest were adult animals of undetermined age. Fibrillation was induced with two types of stimuli directly applied to the heart. The stimuli were a train of rectangular pulses (TP) not synchronized with the ECG, and single pulses (SP) synchronized with and delayed from the R wave. TP type was used in one group with paddle electrodes; and the TP and SP types were used in a second group with hook electrodes. For both types, stimulation started at a low current and was increased until fibrillation was triggered. Once defibrillated, either spontaneously or by electrical shock, the procedure was repeated. Correlation coefficients between FT and VW were low (< 0.4), and scaling of the thresholds to VW resulted in hyperbolic relationship, for all cases, thus suggesting independence of the two parameters. SPDE fell sharply with weight. For values higher than 12 grams it was essentially nonexistent. VW does not have any effect on the FT but it dramatically influences the capacity of the myocardium to revert the arrhythmia by itself.
Assuntos
Cardioversão Elétrica , Miocárdio/patologia , Fibrilação Ventricular/terapia , Animais , Cães , Eletrocardiografia , Tamanho do Órgão , Fibrilação Ventricular/patologia , Fibrilação Ventricular/fisiopatologiaRESUMO
One problem faced by intracardiac conductance volumetry is the non-uniform distribution of the injected current. Salo, in 1989, proposed a method to correct this undesirable effect. The objective here is to test Salo's method in known volumes of simple geometry by obtaining volume profiles. A plastic rod with 15 metallic rings simulated the conductance catheter. Five sections were used for the resistance measurements employing the upper electrode as fixed current source and the lowest one as the shifting source. This is part of Salo's procedure. The source-to-section distance was measured from the moving source to the section (linear definition) or using the equivalent distance concept (Salo's). Thereafter, each sectional resistance set of values was plotted as a function of the inverse of the source-to-section distance (either definition) elevated to an empirical exponent k to obtain the corrected sectional resistance by extrapolation back to zero of the regression line, i.e., a value produced by a source theoretically placed at infinity. In addition, a mathematical analysis was attempted, searching for an optimum k based on minimum volume error. The best volume profiles for two cylinders and a frustum were obtained with k = 2 using the linear definition of distance (errors of -3.49%, -1.25% and -3.65%, respectively). Moreover, the frustum angle was determined within 0.4 degrees (2.7%) of the real value. The theoretical analysis led to an inverse logarithmic relationship between the exponent k and the source-to-section distance.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Volume Cardíaco , Eletrodiagnóstico , Coração/fisiologia , Condutividade Elétrica , Humanos , Modelos Cardiovasculares , Modelos EstruturaisRESUMO
We measured impedance in a cell containing culture broth inoculated with E. coli, before and during bacterial growth. The electrode interface impedance components (Ri, Xi) and the culture medium component Rm were separated by making use of the Warburg's model frequency dependent properties. Measurements were carried out at different frequencies (from 18 Hz to 18 kHz) with a constant current impedance bridge as growth proceeded. It was found that: Growth curves for Ri and Xi showed a similar temporal pattern within the frequency range of 18-100 Hz. Dispersion was not observed in Rm, meaning that the same growth response was obtained within the 18-18,000 Hz range. At low frequency, the resistive and capacitive reactive components, or Rb and Xb, respectively, were directly measured, where Rb = (2.Ri + Rm) and Xb = 2.Xi and, at high frequency (above 5 kHz), Rm was obtained (for Zi is negligible). Thus, Ri was easily discriminated from Rm by simple arithmetic: Ri = [Rb (low f) - Rb (high f)]/2. In four experiments, the maximum spread of Xi, Ri, and Rm was smaller than 5%, indicating good repeatability. There is potential new information in dissecting out the growth curve in three separate component curves.