Jiri Silny

Bio: Jiri Silny is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Motor unit & Filter (signal processing). The author has an hindex of 29, co-authored 63 publications receiving 3136 citations.

Intraluminal Multiple Electric Impedance Procedure for Measurement of Gastrointestinal Motility

Abstract: A new catheter-related procedure for high-resolution measurements of gastrointestinal motility is presented. The method is based on simultaneous acquisition of the electric impedance in the surrounding body volume conductor from a number of annular electrodes, successively arranged on the catheter. The impedance of a volume conductor around the catheter, consisting of a bolus, the organ wall, body fluids, and so forth, has a characteristic value for each segment and phase of contraction wave, as theoretical and experimental investigations revealed. A calculation on the basis of a simplified model reveals that the impedance changes as a logarithmic function of the bolus thickness, in which the highest sensitivity is advantageously obtained at a small lumen size and utilizing unipolar or bipolar electrode setups. The high resolution in time, space, and amplitude of the changes in the bolus shape allow us to use this impedance method for evaluation of functional stages in each measuring segment and of the beginning, end, and type of contraction wave, as well as their characteristics. The unique mechanical properties of the catheter (thinner than 3 mm, several meters long, flexible, closed surface) and the ability to distribute more than 32 measuring segments of different lengths on the catheter make this procedure suitable even for long-term physiologic and pathologic studies of gastrointestinal motility.

Association of apnea and nonacid gastroesophageal reflux in infants: Investigations with the intraluminal impedance technique.

Abstract: An association of apnea and gastroesophageal reflux (GER) was proposed previously. However, pH metry as the standard diagnostic tool for GER only measures acid reflux (pH < 4). It is difficult to interpret studies in infants with a presumed association between apnea and GER based on pH metry because the buffering effect of feeding may result in predominantly nonacid GER. The aim of this study was to investigate the temporal association of apnea and GER with the pH-independent intraluminal impedance technique (IMP). Infants with recurrent regurgitation or respiratory symptoms suggestive of apnea were investigated simultaneously with IMP, pH monitoring, and polygraphy. IMP patterns, pH, oronasal flow, and chest wall movement were recorded and analyzed. In 22 infants, 364 GER episodes were recorded by IMP. One hundred and sixty five apneas were documented by visual validation of polygraph records. Forty-nine apneas (29.7%) were associated with GER; 11 (22.4%) of these showed acid reflux (pH < 4). A significant correlation between the time spent apneic and GER was found (P < 0.001). There is marked association between apnea and gastroesophageal reflux in infants. Patients potentially at risk cannot be reliably identified by pH metry. Its exclusive use is therefore not suitable for the detection of all GER-associated apneas in infants. The pH-independent intraluminal impedance technique has proven to be a sensitive diagnostic tool for this approach.

Improvement of spatial resolution in surface-EMG: a theoretical and experimental comparison of different spatial filters

Abstract: In the present study, different isotropic and anisotropic filters have been compared by means of theoretical field simulations and experiments in volunteers. A tripole model for an excited motor unit (MU) was used as the basis for simulating the spatial extension of the filter response for each of the investigated filters. The spatial extension is an indicative of the spatial resolution. For the experimental validation, the total number of single motor units was not directly investigated, but the signal-to-noise ratio (SNR) has been determined. Therefore, the potential distribution generated on the skin surface during maximum voluntary contraction has been simultaneous spatially filtered with each of the investigated filters. The simulations show that an isotropic spatial filtering procedure reduces the spatial extension of the filter response and improves the spatial resolution of the electromyography (EMG)-recording arrangement in comparison to anisotropic spatial filters up to 30%. In other words, the spatial selectivity of the arrangement is increased. This improvement in the filter performance is more pronounced for MU's located close to the skin surface than for MU's more distantly located. Additionally, this theoretical improvement in selectivity depends on the direction of the excitation spread relative to the filter alignment. However, the investigations also show that isotropic filters offer an advantage, compared to anisotropic filters, only when the investigated MU is located extremely close to the filter input. The results of the simulations can be confirmed by the experimental investigations. An improvement of 11% in the SNR, relative to anisotropic spatial filters, can be established when using an isotropic spatial filter. This experimental improvement in selectivity is less than the theoretical improvement because the experimentally investigated MU's have less portion in the anisotropic range of the filters than the simulated one at best.

The extraction of neural strategies from the surface EMG

Abstract: This brief review examines some of the methods used to infer central control strategies from surface electromyogram (EMG) recordings. Among the many uses of the surface EMG in studying the neural control of movement, the review critically evaluates only some of the applications. The focus is on the relations between global features of the surface EMG and the underlying physiological processes. Because direct measurements of motor unit activation are not available and many factors can influence the signal, these relations are frequently misinterpreted. These errors are compounded by the counterintuitive effects that some system parameters can have on the EMG signal. The phenomenon of crosstalk is used as an example of these problems. The review describes the limitations of techniques used to infer the level of muscle activation, the type of motor unit recruited, the upper limit of motor unit recruitment, the average discharge rate, and the degree of synchronization between motor units. Although the global surface EMG is a useful measure of muscle activation and assessment, there are limits to the information that can be extracted from this signal.

Pediatric Gastroesophageal Reflux Clinical Practice Guidelines: Joint Recommendations of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN)

Abstract: Objective: T o de v elop a North American Society for Pediatric Ga str oen te rol og y , He pat olo gy , and Nut ri tio n (N ASP GH AN) and Eu rop ea n Soc ie ty fo r Pe di atr ic Gas tr oen te ro log y , Hep at ol og y , and Nut rit io n (ES PGH AN ) int er nat io nal con se ns us on th e di agn os is an d ma nag em ent of gas tr oes op hag eal refl ux and gas tr oes op hag eal re flu x di sea se in th e ped ia tr ic po pu la tio n. Methods: An international panel of 9 pediatric gastroenterologists and 2 epidemiologists were selected by both societies, which de v eloped these guidelines based on the Delphi principle. Statements were based on systematic literature searches using the best-av ailable e vidence from PubMed, Cumulati ve Index to Nursing and Allied Health Literature, and bibliographies. The committee con v ened in face-to-face meetings 3 times. Consensus was achie v ed for all recommendations through nominal group technique, a structured, quantitati v e method. Articles were e v aluated using the Oxford Centre for Evidence-based Medicine Le vels of Evidence. Using the Oxford Grades of Recommendation, the quality of e vidence of each of the recommendations made by the committee was determined and is summarized in appendices. Results: More than 600 articles were re vie wed for this work. The document provides e vidence-based guidelines for the diagnosis and management of gastroesophageal reflux and gastroesophageal reflux disease in the pediatric population. Conclusions: Th is do cum ent is int end ed to be us ed in dai ly pra cti ce fo r th e de v el op me nt of fut ure cli ni cal pra ct ic e gu ide lin es and as a bas is for cli ni cal tr ia ls . JP GN 49 :49 8 – 54 7, 20 09 . Ke y Wo rd s: Cli nic al pra ct ic e gu id el ine s — Di agn os tic te sts — Ga str oes op hag ea l refl ux (GE R) — Ga str oes op hag ea l refl ux di sea se (GE RD ) — The rap eut ic mod al iti es. # 20 09 by Eu rop ea n Soc ie ty fo r Pe di atr ic Gas tr oen te ro log y , Hep at ol og y , and Nut rit io n and No rt h Am er ica n So ci ety for Pe dia tri c Ga str oen te rol og y , Hep at ol og y , an d Nu tr iti on

Ablation catheter positioning system

Abstract: A multi-electrode cardiac catheter (10) has pairs of electrodes (13) connected to sensing circuitry (31, 32, 40) to produce a differential signal. The sensing output is sharply defined and self normalizing. Preferably, a catheter ablation tip electrode (12) is an electrode of one pair, and the differential signal becomes non-zero when the tip contacts surrounding tissue. The shape of the differential signal provides information on the degree of electrode contact, as well as on the amount of locally-sensed tissue impedance change. The signal may be used as a trigger enable signal for a cardiac ablation catheter (10), and the applied level of RF power may be controlled based on the indicated degree of electrode contact and value of tissue impedance.

Gastro-oesophageal reflux monitoring: review and consensus report on detection and definitions of acid, non-acid, and gas reflux

Abstract: To date, most concepts on the frequency of gastro-oesophageal reflux episodes and the efficiency of the antireflux barrier have been based on inferences derived from measurement of oesophageal pH. The development of intraluminal impedance monitoring has highlighted the fact that pH monitoring does not detect all gastro-oesophageal reflux events when little or no acid is present in the refluxate, even if special pH tracing analysis criteria are used. In November 2002, a workshop took place at which 11 specialists in the field of gastro-oesophageal reflux disease discussed and criticised all currently available techniques for measurement of reflux. Here, a summary of their conclusions and recommendations of how to achieve the best results from the various techniques now available for reflux measurement is presented.