| 1. |
- Benouar, Sara, et al.
(författare)
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Classification of impedance cardiography dZ/dt complex subtypes using pattern recognition artificial neural networks
- 2021
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : Walter de Gruyter. - 1862-278X .- 0013-5585. ; 66:5, s. 515-527
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Tidskriftsartikel (refereegranskat)abstract
- In impedance cardiography (ICG), the detection of dZ/dt signal (ICG) characteristic points, especially the X point, is a crucial step for the calculation of hemodynamic parameters such as stroke volume (SV) and cardiac output (CO). Unfortunately, for beat-to-beat calculations, the accuracy of the detection is affected by the variability of the ICG complex subtypes. Thus, in this work, automated classification of ICG complexes is proposed to support the detection of ICG characteristic points and the extraction of hemodynamic parameters according to several existing subtypes. A novel pattern recognition artificial neural network (PRANN) approach was implemented, and a divide-and-conquer strategy was used to identify the five different waveforms of the ICG complex waveform with output nodes no greater than 3. The PRANN was trained, tested and validated using a dataset from four volunteers from a measurement of eight electrodes. Once the training was satisfactory, the deployed network was validated on two other datasets that were completely different from the training dataset. As an additional performance validation of the PRANN, each dataset included four volunteers for a total of eight volunteers. The results show an average accuracy of 96% in classifying ICG complex subtypes with only a decrease in the accuracy to 83 and 80% on the validation datasets. This work indicates that the PRANN is a promising method for automated classification of ICG subtypes, facilitating the investigation of the extraction of hemodynamic parameters from beat-to-beat dZ/dt complexes.
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| 2. |
- Bissig, Hugo, et al.
(författare)
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Calibration of insulin pumps based on discrete doses at given cycle times
- 2023
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : De Gruyter Open Ltd. - 1862-278X .- 0013-5585. ; 68:1, s. 67-77
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Tidskriftsartikel (refereegranskat)abstract
- One application in the medical treatment at very small flow rates is the usage of an Insulin pump that delivers doses of insulin at constant cycle times for a specific basal rate as quasi-continuous insulin delivery, which is an important cornerstone in diabetes management. The calibration of these basal rates are performed by either gravimetric or optical methods, which have been developed within the European Metrology Program for Innovation and Research (EMPIR) Joint Research Project (JRP) 18HLT08 Metrology for drug delivery II (MeDDII). These measurement techniques are described in this paper, and an improved approach of the analytical procedure given in the standard IEC 60601-2-24:2012 for determining the discrete doses and the corresponding basal rates is discussed in detail. These improvements allow detailed follow up of dose cycle time and delivered doses as a function of time to identify some artefacts of the measurement method or malfunctioning of the insulin pump. Moreover, the calibration results of different basal rates and bolus deliveries for the gravimetric and the optical methods are also presented. Some analysis issues that should be addressed to prevent misinterpreting of the calibration results are discussed. One of the main issues is the average over a period of time which is an integer multiple of the cycle time to determine the basal rate with the analytical methods described in this paper.
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| 3. |
- Bissig, Hugo, et al.
(författare)
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In-line measurements of the physical and thermodynamic properties of single and multicomponent liquids
- 2023
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : De Gruyter Open Ltd. - 1862-278X .- 0013-5585. ; 68:1, s. 39-50
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Tidskriftsartikel (refereegranskat)abstract
- Microfluidic devices are becoming increasingly important in various fields of pharmacy, flow chemistry and healthcare. In the embedded microchannel, the flow rates, the dynamic viscosity of the transported liquids and the fluid dynamic properties play an important role. Various functional auxiliary components of microfluidic devices such as flow restrictors, valves and flow meters need to be characterised with liquids used in several microfluidic applications. However, calibration with water does not always reflect the behaviour of the liquids used in the different applications. Therefore, several National Metrology Institutes (NMI) have developed micro-pipe viscometers for traceable inline measurement of the dynamic viscosity of liquids used in flow applications as part of the EMPIR 18HLT08 MeDDII project. These micro-pipe viscometers allow the calibration of any flow device at different flow rates and the calibration of the dynamic viscosity of the liquid or liquid mixture used under actual flow conditions. The validation of the micro-pipe viscometers has been performed either with traceable reference oils or with different liquids typically administered in hospitals, such as saline and/or glucose solutions or even glycerol-water mixtures for higher dynamic viscosities. Furthermore, measurement results of a commercially available device and a technology demonstrator for the inline measurement of dynamic viscosity and density are presented in this paper. © 2022 the author(s)
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| 4. |
- Buehler, S., et al.
(författare)
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The shape of intratidal resistance-volume and compliance-volume curves in mechanical ventilation - an animal study
- 2013
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : Walter de Gruyter GmbH. - 1862-278X .- 0013-5585. ; 58
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Tidskriftsartikel (refereegranskat)abstract
- In respiratory system mechanics, the shape of the intratidal pulmonary compliance-volume curve can be used to detect atelectasis or overdistension in the mechanically ventilated lung and thus to optimise the ventilator setting in terms of positive end-expiratory pressure (PEEP) and tidal volume (V-T). To this end, a set of shape-categories had been suggested. Furthermore, a characteristic behaviour of the intratidal resistance is expected as a consequence of alveolar recruitment and overdistension of the airways. We inspect the intratidal compliance and resistance profiles in mechanically ventilated pigs and suggest a classification into slope-categories for the resistance profile which could be used in combination with the compliance shape-categories to optimize PEEP and V-T.
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| 5. |
- Chow, Winnie W. Y., et al.
(författare)
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Influence of bio-coatings on the recording performance of neural electrodes
- 2014
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : Walter de Gruyter GmbH. - 1862-278X .- 0013-5585. ; 59:4, s. 315-322
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Tidskriftsartikel (refereegranskat)abstract
- Neural probes are complex devices consisting of metallic (often Pt based) electrodes, spread over an insolating/dielectric backbone. Their functionality is often limited in time because of the formation of scaring tissues around the implantation tracks. Functionalization of the probes surface can be used to limit the glial scar reaction. This is however challenging, as this treatment has to be equally efficient on all probe surfaces (metallic as well as dielectric) and should not influence the electrodes performances. This paper presents a novel technique to functionalize recording neural probes with hyaluronic acid (HyA), a major component of the extracellular matrix (ECM). HyA and the probe surface are both modified to make the reaction feasible: HyA is chemically functionalized with SS-pyridine groups while the probe surfaces are silanized. The thiol groups thus introduced on the probe surface can then react with the HyA SS-pyridine group, resulting in a covalent bonding of the latter on the former. The electrodes are protected by introducing a pretreatment step, namely an additional hyaluronic acid layer on the platinum electrode, prior to the silanization process, which was found to be effective in reducing electrode impedance under optimized conditions.
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| 6. |
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| 7. |
- Dombovari, Balazs, et al.
(författare)
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In vivo validation of the electronic depth control probes
- 2014
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : Walter de Gruyter GmbH. - 1862-278X .- 0013-5585. ; 59:4, s. 283-289
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we evaluated the electrophysiological performance of a novel, high-complexity silicon probe array. This brain-implantable probe implements a dynamically reconfigurable voltage-recording device, coordinating large numbers of electronically switchable recording sites, referred to as electronic depth control (EDC). Our results show the potential of the EDC devices to record good-quality local field potentials, and single- and multiple-unit activities in cortical regions during pharmacologically induced cortical slow wave activity in an animal model.
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| 8. |
- Hemm-Ode, Simone, et al.
(författare)
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Correlation between laser Doppler measurements and anatomy during deep brain stimulation surgery
- 2012
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Ingår i: Biomedical Engineering. - Berlin : Walter de Gruyter. - 0006-3398 .- 1573-8256. ; 57
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionIn Deep Brain Stimulation (DBS) the save, accurate and precise electrode implantation is essential. We have previously presented an optical technique for intra-operative measurements during DBS implantation. The aim of the present study was to establish the link between anatomy and total light intensity (TLI, the greyness of the tissue) and microvascular perfusion recordings.MethodsTwelve patients (6 subthalamic nucleus STN, 6 ventral intermediate nucleus Vim) referred for unilateral or bilateral DBS-implantation for the treatment of essential tremor or Parkinson’s disease were included in the study. Stereotactic CT imaging was used for planning of the trajectories and targets (n=22). Measurement of the TLI and the microvascular perfusion were performed in mm-steps along the trajectory. TLI and perfusion data were post-processed to “optical trajectories” ranging from the cortex towards the target. These were compared with anatomy along the final trajectories by the use of a brain atlas and Surgiplan.ResultsPost-processing of the TLI signal showed a clear relationship with anatomy. Characteristic median curves were determined. The curve normally started with low values for STN and Vim patients when in cortex. When the probe entered white matter the TLI increased and stayed at this level until it passed in the vicinity to putamen, caudate nucleus or ventricle. A statistical significant difference (p<0.05) could be shown between white matter and putamen and between white matter and the target area. Concerning microvascular perfusion, high values were often seen in the cortex and low ones in white matter (significant statistical difference: p<0.05). In one case a small bleeding was suspected during surgery with the optical technique. This was confirmed with post-operative CT.ConclusionIn summary the optical technique show promising results and typical trajectories were defined towards the STN and Vim, but further evaluation is necessary in order to refine the “optical bar codes” towards specific DBS-targets.
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| 9. |
- Hey, Matthias, et al.
(författare)
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The Intra-Cochlear Impedance-Matrix (IIM) test for the Nucleus (R) cochlear implant
- 2015
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Ingår i: Biomedizinische Technik / Biomedical Engineering. - : Walter de Gruyter GmbH. - 1862-278X. ; 60:2, s. 123-133
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To describe the principles and operation of a new telemetry-based function test for the Nucleus (R) cochlear implant, known as the CS19 Intra-Cochlear Impedance Matrix (IIM) and to present results from a multicentre clinical study to establish reproducibility (test-retest reliability) and normative ranges. Method: The IIM test measures bipolar impedances between all electrode pairs and employs a normalization procedure based on common ground impedances in order to identify abnormal current paths among electrodes. Six European clinics collected IIM data from a total of 192 devices. Results: Reproducibility was high between initial and repeat measurements. The normative analysis demonstrated narrow ranges among devices after normalization of impedance data. The IIM is able to identify abnormal current paths that are not evident from standard impedance telemetry and may otherwise only be found utilising average electrode voltage measurements (AEV). Conclusions: The IIM test was found to be straightforward to perform clinically and demonstrated reproducible data with narrow ranges in normally-functioning devices. Because this test uses a very low stimulation level the IIM test is well suited for children or multiply handicapped CI users who cannot reliably report on their auditory percepts. The new algorithms show potential to improve implant integrity testing capabilities if implemented in future clinical software.
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| 10. |
- Håkansson, Joakim, et al.
(författare)
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De- and recellularized urethral reconstruction with autologous buccal mucosal cells implanted in an ovine animal model
- 2023
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : De Gruyter Open Ltd. - 1862-278X .- 0013-5585. ; 68:5, s. 493-
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Tidskriftsartikel (refereegranskat)abstract
- Patients with urethral stricture due to any type of trauma, hypospadias or gender dysphoria suffer immensely from impaired capacity to urinate and are in need of a new functional urethra. Tissue engineering with decellularization of a donated organ recellularized with cells from the recipient patient has emerged as a promising alternative of advanced therapy medicinal products. The aim of this pilot study was to develop an ovine model of urethral transplantation and to produce an individualized urethra graft to show proof of function in vivo. Donated urethras from ram abattoir waste were decellularized and further recellularized with autologous buccal mucosa epithelial cells excised from the recipient ram and expanded in vitro. The individualized urethral grafts were implanted by reconstructive surgery in rams replacing 2.5 ± 0.5 cm of the native penile urethra. After surgery optimization, three ram had the tissue engineered urethra implanted for one month and two out of three showed a partially regenerated epithelium. Further adjustments of the model are needed to achieve a satisfactory proof-of-concept; however, we interpret these findings as a proof of principle and a possible path to develop a functional tissue engineered urethral graft with de- and recellularization and regeneration in vivo after transplantation.
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