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Author: Welsch, C. ×

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Now showing 1 - 9 of 9
  • Publication
    Capnography monitoring of non-anesthesiologist provided sedation during percutaneous endoscopic gastrostomy placement: A prospective, controlled, randomized trial
    ( 2020)
    Peveling-Oberhag, J.
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    Michael, F.
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    Tal, A.
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    Welsch, C.
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    Vermehren, J.
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    Farnik, H.
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    Grammatikos, G.
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    Lange, C.
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    Walter, D.
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    Blumenstein, I.
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    Filmann, N.
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    Herrmann, E.
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    Albert, J.
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    Zeuzem, S.
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    Bojunga, J.
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    Friedrich-Rust, M.
    Background and Aim: A number of studies were able to show a reduction of hypoxemia episodes during procedural sedation through the use of capnography (CA). The present study investigates the number of episodes of hypoxemia during percutaneous endoscopic gastrostomy (PEG) placement with propofol sedation comparing standard monitoring (SM) versus SM with additional CA surveillance. Methods: In this single center randomized controlled trial, 150 patients were prospectively randomized 1:1 in either the SM group or the CA group after stratification for ASA class, PEG method (push or pull method), presence of head and neck tumor, and tracheostomy. CA analysis was performed for all patients but was blinded for the endoscopic team in the SM group. Results: In the SM group, 57% episodes of hypoxemia (SpO2 < 90% for > 15 s) and 41% episodes of severe hypoxemia (SpO2 < 85% for > 15 s) were observed in comparison with 28% and 20% in the CA group, respectively. Odds ratios for hypoxemia and severe hypoxemia were 0.29 (confidence interval 0.15-0.57; P = 0.0005) and 0.35 (confidence interval 0.17-0.73; P = 0.008) in favor of the CA group. On average, CA was able to detect imminent mild and severe hypoxemia 83 and 99 s before standard monitoring. Standard monitoring represented an independent risk factor for hypoxemia and severe hypoxemia. Conclusions: Respiratory complications of sedation during PEG placement are frequent events. CA is able to detect imminent hypoxemia at an early time point. This allows an early intervention and consecutively the avoidance of mild and severe hypoxemia. Therefore, CA monitoring can be recommended particularly during PEG insertion procedures.
  • Publication
    Omega-3 and -6 fatty acid plasma levels are not associated with liver cirrhosis-associated systemic inflammation
    ( 2019)
    Schwarzkopf, K.M.
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    Queck, A.
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    Thomas, D.
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    Angioni, C.
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    Cai, C.
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    Freygang, Y.
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    Rüschenbaum, S.
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    Geisslinger, G.
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    Zeuzem, S.
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    Welsch, C.
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    Lange, C.M.
    Background: Liver cirrhosis is associated with profound immunodysfunction, i.e. a parallel presence of chronic systemic inflammation and immunosuppression, which can result in acute-on-chronic liver failure (ACLF). Omega-3 fatty acids are precursors of pro-resolving mediators and support the resolution of inflammation. Objective: The aim of this study was to determine plasma levels of omega-3 fatty acids in patients with liver cirrhosis and ACLF. Methods: Patients with liver cirrhosis with and without ACLF were enrolled in a prospective cohort study and analyzed post-hoc for the present sub-study. Clinical data and biomaterials were collected at baseline and at day 7, 28 and after 3 months of follow-up. Plasma concentrations of arachidonic acid (ARA) and docosahexaenoic acid (DHA), which represent key omega-6 and -3 fatty acids, respectively, were quantified and associated with markers of systemic inflammation and severity of liver cirrhosis. Results: A total of 117 patients were included in the present analyses. Of those, 26 (22.2%), 51 (43.6%) and 40 (34.2%) patients had compensated or decompensated liver cirrhosis, and ACLF. Plasma levels of ARA and DHA were similar in patients with compensated cirrhosis, decompensated cirrhosis, and ACLF. Furthermore, no significant association between plasma ARA or DHA and C-reactive protein or peripheral blood leukocytes were observed (P>0.05). Conclusion: In our study plasma levels of key omega-3 and omega-6 fatty acid are neither associated with the severity of liver cirrhosis nor with liver-cirrhosis-associated systemic inflammation.
  • Publication
    Prolonged Corrosion Stability of a Microchip Sensor Implant during In Vivo Exposure
    ( 2018)
    Glogener, P.
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    Krause, M.
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    Katzer, J.
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    Schubert, M.A.
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    Birkholz, M.
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    Bellmann, O.
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    Kröger-Koch, C.
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    Hammon, H.M.
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    Metges, C.C.
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    Welsch, C.
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    Ruff, R.
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    Hoffmann, K.P.
    A microelectronic biosensor was subjected to in vivo exposure by implanting it in the vicinity of m. trapezii (Trapezius muscle) from cattle. The implant is intended for the continuous monitoring of glucose levels, and the study aimed at evaluating the biostability of exposed semiconductor surfaces. The sensor chip was a microelectromechanical system (MEMS) prepared using 0.25 µm complementary metal-oxide-semiconductor CMOS/BiCMOS technology. Sensing is based on the principle of affinity viscometry with a sensoric assay, which is separated by a semipermeable membrane from the tissue. Outer dimensions of the otherwise hermetically sealed biosensor system were 39 × 49 × 16 mm. The test system was implanted into cattle in a subcutaneous position without running it. After 17 months, the device was explanted and analyzed by comparing it with unexposed chips and systems. Investigations focused on the MEMS chip using SEM, TEM, and elemental analysis by EDX mapping. The sensor chip turned out to be uncorroded and no diminishing of the topmost passivation layer could be determined, which contrasts remarkably with previous results on CMOS biosensors. The negligible corrosive attack is understood to be a side effect of the semipermeable membrane separating the assay from the tissue. It is concluded that the separation has enabled a prolonged biostability of the chip, which will be of relevance for biosensor implants in general.
  • Publication
    Ongoing liver inflammation in patients with chronic hepatitis C and sustained virological response
    ( 2017)
    Welsch, C.
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    Efinger, M.
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    Wagner, M. von
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    Herrmann, E.
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    Zeuzem, S.
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    Welzel, T.M.
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    Lange, C.M.
    Background: Novel direct-acting antiviral DAA combination therapies tremendously improved sustained virologic response (SVR) rates in patients with chronic HCV infection. SVR is typically accompanied by normalization of liver enzymes, however, hepatic inflammation, i.e. persistently elevated aminotransferase levels may persist despite HCV eradication. Aim: To investigate prevalence and risk factors for ongoing hepatic inflammation after SVR in two large patient cohorts. Methods: This post-hoc analysis was based on prospectively collected demographic and clinical data from 834 patients with SVR after HCV treatment with either PegIFN- or DAA-based treatment regimens from the PRAMA trial (n = 341) or patients treated at our outpatient clinic (n = 493). Results: We observed an unexpected high prevalence of post-SVR inflammation, including patients who received novel IFN-free DAA-based therapies. Up to 10% of patients had ongoing elevation of aminotransferase levels and another 25% showed aminotransferase activity above the so-called healthy range. Several baseline factors were independently associated with post-SVR aminotransferase elevation. Among those, particularly male gender, advanced liver disease and markers for liver steatosis were strongly predictive for persistent ALT elevation. The use of IFN-based antiviral treatment was independently correlated with post-SVR inflammation, further supporting the overall benefit of IFN-free combination regimens. Conclusion: This is the first comprehensive study on a large patient cohort investigating the prevalence and risk factors for ongoing liver inflammation after eradication of HCV. Our data show a high proportion of patients with ongoing hepatic inflammation despite HCV eradication with potential implications for the management of approximately one third of all patients upon SVR.
  • Publication
    System integration of a silicone-encapsulated glucose monitor implant
    ( 2014)
    Birkholz, M.
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    Glogener, P.
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    Basmer, T.
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    Glös, F.
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    Genschow, D.
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    Welsch, C.
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    Ruff, R.
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    Hoffmann, K.-P.
    An intelligent sensor implant for continuous glucose monitoring is presented as intended for use in the human interstitial. The sensor operates by the principle of affinity viscosimetry, by which glucose concentrations are determined with a microelectromechanical system (MEMS) measuring the glucose-dependent viscosity of a concanavalinA-dextran assay. Data transmission is performed in the 403MHz band as approved for medical implant communication services (MICS). The sensor system is encapsulated in silicone to enable a sufficient hermiticity for time spans of weeks and months. In vitro testing revealed no corrosion of system components for a period of months.
  • Publication
    Development, manufacturing and application of double-sided flexible implantable microelectrodes
    ( 2014)
    Poppendieck, W.
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    Sossalla, A.
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    Krob, M.O. orcid-logo
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    Welsch, C.
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    Nguyen, T.A.K.
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    Gong, W.
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    DiGiovanna, J.
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    Micera, S.
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    Merfeld, D.M.
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    Hoffmann, K.P.
    Many neuroprosthetic applications require the use of very small, flexible multi-channel microelectrodes (e.g. polyimide-based film-like electrodes) to fit anatomical constraints. By arranging the electrode contacts on both sides of the polyimide film, selectivity can be further increased without increasing size. In this work, two approaches to create such double-sided electrodes are described and compared: sandwich electrodes prepared by precisely gluing two single-sided structures together, and monolithic electrodes created using a new double-sided photolithography process. Both methods were successfully applied to manufacture double-sided electrodes for stimulation of the vestibular system. In a case study, the electrodes were implanted in the semicircular canals of three guinea pigs and proven to provide electrical stimulation of the vestibular nerve. For both the monolithic electrodes and the sandwich electrodes, long-term stability and functionality was observed over a period of more than 12 months. Comparing the two types of electrodes with respect to the manufacturing process, it can be concluded that monolithic electrodes are the preferred solution for very thin electrodes (<20 mm), while sandwich electrode technology is especially suitable for thicker electrodes (40-50 mm).
  • Publication
    Sandwich electrode technology for precise vestibular electrodes with high reliability
    ( 2013)
    Poppendieck, W.
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    Krob, M.-O. orcid-logo
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    Welsch, C.
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    Merfeld, D.
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    Micera, S.
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    Hoffmann, K.-P.
    Development of multi-channel microelectrodes for interfacing the vestibular system makes high demands on fabrication technology. To be able to insert such electrodes in the semicircular canals, adequate stiffness of the structures is required. Moreover, a double-sided arrangement of the electrode contacts is desired, in order to increase selectivity. In this work, two approaches are presented and compared to create such electrode systems. While using a double-sided photolithography process is a suitable method to create very thin and flexible monolithic double-sided electrode structures, application in a vestibular prosthesis demands fabrication of thicker and stiffer electrodes. For this purpose, sandwich electrode technology is the preferred method. Here, two single-sided polyimide thin-film structures are precisely glued together to form a sandwich-like electrode with active contacts on both sides of the structure. For vestibular prostheses, this technology allows a faster and more reliable production of vestibular microelectrodes.
  • Publication
  • Publication
    Development of multi-channel intramuscular EMG recording electrodes
    ( 2013)
    Poppendieck, W.
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    Muceli, S.
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    Welsch, C.
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    Krob, M.-O. orcid-logo
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    Sossalla, A.
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    Yoshida, K.
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    Farina, D.
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    Hoffmann, K.-P.
    A 16-channel intramuscular electrode system for high-resolution EMG recording was developed and fabricated. This system consists of a flexible thread-like thin-film structure based on polyimide, which is attached to a conventional needle cannula by the use of a guiding filament. This needle is removed after insertion, leaving only the polyimide structure within the muscle. The electrode systems were electrically characterized and successfully evaluated in human subjects for recording of high-resolution EMG signals and single motor unit activity.