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Mirkovic T.,University of Ljubljana | Knezevic I.,University of Ljubljana | Radan I.,University of Ljubljana | Rozman J.,Center for Implantable Technology and Sensors | And 2 more authors.
Signa Vitae | Year: 2012

Activation of the parasympathetic pathway leads to negative chronotropic, dromotropic, and inotropic changes of heart function. The ability to selectively stimulate certain superficial compartments of peripheral nerves has been demonstrated previously. The aim of the present study was to find a clinically acceptable selective biphasic vagus nerve stimulation technique, which could allow gradual regulation of heart rate and systemic arterial pressure. In two patients, the left vagus nerve was stimulated with a combination of quasi-trapezoidal cathodic and rectangular anodic current pulses with different stimulation frequencies (10Hz, 20Hz, 30Hz) and increasing current. The heart rate and systemic arterial pressure decreased with increasing current at all different stimulation frequencies (p<0.05). The heart rate and arterial pressure response was more gradual with 10Hz compared to 20Hz/30Hz vagus nerve stimulation (p<0.05). In conclusion, selective vagus nerve stimulation, with a combination of quasi-trapezoidal cathodic and rectangular anodic current pulses at 10Hz, offers gradual heart rate and systolic arterial pressure control.

Lainscak M.,University Clinic of Respiratory and Allergic Diseases Golnik | Lainscak M.,Applied Cachexia Research | Podbregar M.,University of Ljubljana | Kovacic D.,General Hospital Celje | And 3 more authors.
Respiratory Medicine | Year: 2011

Chronic obstructive pulmonary disease (COPD) frequently coexists in patients with chronic heart failure (CHF) and is a key factor for beta blocker underprescription and underdosing. This study compared effects of bisoprolol and carvedilol in patients with both conditions. This was a randomized open-label study, of bisoprolol and carvedilol during initiation and uptitration to target of maximal tolerated dose. Pulmonary function testing, 12-lead electrocardiogram, and N-terminal pro brain natriuretic peptide were measured at baseline and follow-up. We randomized 63 elderly patients (73±9 years, 81 men, left ventricular ejection fraction 33±7) with mild to moderate CHF (54 New York Heart Assocation class II) and moderate to severe COPD (76 Global initiative for chronic Obstructive Lung Disease stage 2). Target dose was tolerated by 31 (49) patients and 19 (30) patients experienced adverse events during follow-up (19 bisoprolol, 42 carvedilol, p = 0.045). Study medication had to be withdrawn in 8 (13) patients (bisoprolol: 2 due to hypotension, 1 due to bradycardia; carvedilol: 2 due to hypotension and 1 due to wheezing, dyspnoea, and oedema, respectively). Forced expiratory volume in 1 st second significantly increased in bisoprolol (1561±414ml to 1698±519ml, p = 0.046) but not carvedilol (1704±484 to 1734±548, p = 0.44) group. Both agents reduced heart rate (bisoprolol: 75±14 to 68±10, p = 0.007; carvedilol 78±14 to 72±12, p = 0.016) and had no effect on N-terminal pro brain natriuretic peptide. Beta blockers frequently caused adverse events, and thus 49 of patients could tolerate the target dose. Bisoprolol induced demonstrable improvement in pulmonary function and caused less adverse events. © 2011 Elsevier Ltd. All rights reserved.

Hocevar Z.,University of Ljubljana | Rozman J.,Center for Implantable Technology and Sensors | Paska A.V.,University of Ljubljana | Frangez R.,University of Ljubljana | And 2 more authors.
Journal of Ultrasound in Medicine | Year: 2012

Objectives - This study evaluated the possible effects of ultrasound (US) on gene expression in brain tissue of rat embryos. Methods - Four groups (n = 5 each) of pregnant Wistar Han rats were exposed to US for different durations (55, 100, 145, and 195 seconds) via a multifrequency transducer in the 2-dimensional imaging mode with a pulse duration of 1.29 microseconds, a pulse repetition frequency of 1 kHz, and a derated spatial-peak pulse-average intensity of 222.4 W/cm 2 on day 5, 9, 7, or 13 of gestation. Gene expression profiling was performed in fetal brain tissue (n = 5 per group) by quantitative reverse transcription-polymerase chain reaction arrays. Results - The results indicated substantial alterations in gene expression. The most differentially expressed genes were Adamts5, Gadd45a, Npy2r, and Chrna1, which are implicated in important developmental signaling pathways. Conclusions - On the basis of our findings, routine short US examinations for monitoring fetal development are not contraindicated, but prolonged exposures should be used only when needed to obtain important diagnostic information. © 2012 by the American Institute of Ultrasound in Medicine.

Rozman J.,Center for Implantable Technology and Sensors | Peclin P.,Center for Implantable Technology and Sensors | Mehle A.,University of Ljubljana | Sala M.,Slovenian National Institute of Chemistry
Australasian Physical and Engineering Sciences in Medicine | Year: 2014

In this study, the electrochemical performance of platinum electrodes within a multi-electrode spiral cuff to be used for selective nerve stimulation was investigated. The original cuff, simplified into a half-cuff, contained a single row of nine electrodes (0.5 ×2 mm) at a distance of 2 mm from its inner surface. Cyclic voltammetry was used to investigate the electrochemical reactions at the electrode–electrolyte interface, to define a potential window within which the electrode could be safely used in selective nerve stimulation, to calculate the charge injection capacity and cathodal charge storage capacity. Voltage transients retrieved during excitation with quasitrapezoidal biphasic current pulses, tested by selective nerve stimulation of the isolated porcine left cervical vagus nerve segment, were used to determine the maximum polarization across the electrode–electrolyte interface and to calculate cathodic charge injection capacity of the electrode. The results show that the most negative and most positive potentials across the electrode–electrolyte interface reached −0.54 and 0.59 V; these did not exceed the safe potential limits for water electrolysis. Furthermore, the time integral of the cathodic current by cyclic voltammetry measured over the potential range of water electrolysis, actually representing the cathodal charge storage capacity, was approximately −4mC cm−2. The charge injection capacity, representing the maximum charge density injected in a current stimulation pulse, using only reversible processes, however, was around 75µCcm−2. In conclusion, both, the tested stimulation pulse and electrode are suitable for efficient and safe selective nerve stimulation. © 2014, Australasian College of Physical Scientists and Engineers in Medicine.

Peclin P.,Center for Implantable Technology and Sensors | Krajnik J.,University of Ljubljana | Acimovic-Janezic R.,University of Ljubljana | Stanic U.,Jozef Stefan Institute | Rozman J.,Center for Implantable Technology and Sensors
2014 37th International Convention on Information and Communication Technology, Electronics and Microelectronics, MIPRO 2014 - Proceedings | Year: 2014

Functional electrical stimulation (FES) of the common peroneal nerve (CPN), to correct gait, has been shown to be a useful means for the restoration of functional movement in the lower extremities of hemiplegic individuals. Motor function over a twenty-nine year period of selective stimulation of the CPN with an implantable stimulator to correct drop-foot in a 56 year old patient with left-sided hemiplegia, was evaluated. Partial restoration of dorsal flexion and well balanced eversion of the affected foot was achieved by selective stimulation of superficial region of the CPN innervating mostly the tibialis anterior and partly peroneus longus and peroneus brevis muscles. It was shown that the system is suitable for very long-term FES providing improved muscle function. Namely, even after 29 years of daily FES of the CPN, a functional and reliable recruitment of fibres within the CPN was still achieved, thus providing an appropriate dorsal flexion and eversion of the affected foot. It was found that the stimulation-associated-mechanical trauma to the CPN elicited some minor non-age-related loss of the larger myelinated nerve fibres. Electrophysiological and biomechanical measurements however, have not revealed any functional signs which could be attributed to the damage of the CPN. © 2014 MIPRO.

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