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Biomedical subjects

G Rau

Publications and source records attributed to G Rau.

211 records · Page 12Linked to original sources
PubMedDate not supplied

[Arm motion analysis: a new method and its clinical application].

AIM: An investigation into the objective criteria of shoulder mobility possesses special meaning for diagnostic documentation, the evaluation of therapy and the effects of rehabilitation in the treatment of diseases of the shoulder. In order to ascertain the criteria which characterise shoulder mobility, it is necessary to have a tool available that is objective, comparable and allows the complexity, variability and range of motion to be recorded. Motion analysis represents one such standard procedure used to measure joint movement. METHOD: Accordingly, a marker- based motion analysis of the wrist and elbow, a marker-based three-dimensional motion analysis system for the upper extremities was developed. We evaluated 10 healthy subjects without shoulder conditions and 8 patients with impingement syndrome (7 operative, 1 conservative therapy). RESULTS: The healthy subjects revealed a reproducible motion curve for the specific motion tested. The curves were defined as the normal standard and we used them for comparative purposes. In the treatment group, an improvement of the 3D range of motion could be documented for the affected shoulder following rehabilitation. CONCLUSION: It can be stated that this newly developed marker-based procedure for the three-dimensional motion analysis is suitable for recording complex unconstrained movements. This was found to be more relevant for the assessment of the ability of patients to manage the physical demands of daily living than traditional clinical tests. Furthermore, the information gained from motion analysis of the upper extremities will play a valuable role in the future for quality control during diagnosis and treatment, as well as for the design of shoulder rehabilitation programs.

Adult↗
PubMedDate not supplied

A new procedure for the registration of the visual-evoked cortical potential by multichannel recording of the gradient distribution.

A new bipolar multichannel visual-evoked cortical potential (VECP) procedure is presented, which can supply objective information on visual field losses. The electrical potential is recorded from 11 electrodes applied to the back of the head in the form of an equidistant rectangular grid. Each neighbouring pair of electrodes feeds one of 14 bipolar channels. The adjacent horizontal and vertical channels are used to calculate an approximation to the direction and amplitude of the electrical field gradients. The gradient distribution is represented by a map of arrows (gradient map) for every instant of the sweep, so that the whole sweep can be plotted as a time series of gradient maps. The maps are easy to scale and are well suited for visual evaluation. Twenty normal subjects were stimulated using checkerboard reversal, partial field patterns to simulate visual field defects. The stimulated area varied between full-, half- and quarter-field, and the particular area stimulated could be clearly seen in the resulting gradient maps. Additionally, we developed a computerized classification procedure that detected 86% of the disturbed visual fields from the gradient recordings.

Adult↗
PubMedDate not supplied

Area-to-amplitude ratio of the terminal phase of the belly-tendon detected motor unit potentials could be used to recognize reinnervated motor units.

Besides the increased number of fibres, the reinnervated motor units (MUs) are characterised by an increased scattering the end-plates, greater desynchronization in the fibres' activation, greater dispersion in the diameters of the MU fibres and thus in propagation velocities along them. As a result, desynchronization in the moments, at which the excitation waves reach the fibres' ends, increases in reinnervated MUs. The possibility to recognize reinnervated MUs in short (hand) muscles on the basis of changes in duration of the terminal (second) phase of the belly-tendon detected motor unit potentials (MUPs) was examined by numerical experiments. A convolution model that took into account the finite fibre length, was used to calculate MUPs for distances typical of surface detection. It was shown that the ratio between the area of the terminal phase and its amplitude, as a measure of duration of the terminal phase, was sensitive to desynchronisation of the waves of excitation. The ratio was independent of the distance from the MU axis and of the volume conductor properties. Basing on the results obtained, we can conclude that the ratio reflects main functional compensations in reinnervated MUs and could be used for discrimination between reinnervated and normal MUs.

Electromyography↗
PubMedDate not supplied

A noninvasive EMG technique for investigating the excitation propagation in single motor units.

A new EMG recording technique which is based on a spatially filtering surface multi-electrode array enables, with its high spatial resolution, the noninvasive investigation of single motor unit (MU) excitations. This recording technique was applied to study the propagation velocity within single, superficial MUs of lower arm muscles. The conduction velocity (CV) was estimated by time shifts between action potentials (APs) recorded at different positions along the muscle fibres. Several signal characteristics to define this time shift were compared in regard of their influence on the reliability of CV values. Best results were obtained by calculating the time shift between main peak maxima, with a standard deviation found for the CV values from single APs in the range of 4 to 25%. The disturbance by signal noise could be reduced by the application of approximating cubic spline functions. The CV values showed a remarkable variability between different sites along the single MU muscle fibres.

Action Potentials↗
PubMedDate not supplied

A novel implantable electromechanical ventricular assist device. First acute animal testing.

A novel ventricular assist device (HIA-EMLVAD-AT1, Helmholtz Institute Aachen-Electromechanical Left Ventricular Assist Device-Animal Test Version 1), driven by a uniformly and unidirectionally rotating actuator and a patented hypocycloidic pusherplate displacement gear unit, was developed and tested in an acute animal experiment. The excellent free filling behavior of the pump chamber with a stroke volume of 65 ml is obtained by a 2:3 ejection-filling time relationship. The uniform motor rotation facilitates simple sensorless pre and afterload detection by motor current analysis. In contrast to common apical cannulation, the inlet cannula was placed via the left atrium through the mitral valve into the left ventricle. This connection mode is preferable for left ventricular recovery and preservation. Left atrial, left ventricular, and aortic pressure curves, as well as pulmonary artery flow data, were obtained. The data show very effective unloading of the natural ventricle and demonstrate the feasibility of this novel assist device. Directions for further improvement of technical features were also identified.

Animals↗