Nicht-invasive Beatmung bei Frühgeborenen

Einleitung: Nicht-invasive Beatmung (NIV) wird bei der Mehrheit der ELBW und VLBW Frühgeborenen eingesetzt. Dennoch existieren bis dato keine Leitlinien zur Entwöhnung (Weaning), vielmehr unterliegt dieses häufig der subjektiven Einschätzung des Teams. Um die Beurteilung der Atemarbeit unter NIV zu standardisieren, wird seit 2017 auf unseren neonatologischen Intensivstationen routinemäßig der Silverman-Anderson-Score (SAS) während der Pflegerunden erhoben. Ziel der Studie war es zu untersuchen, welche Faktoren die Weaningentscheidungen beeinflussen und welche Rolle der SAS hierbei spielt. Methoden: Nach Einführung des SAS auf Station wurden über den Zeitraum von 16 Monaten prospektiv bei 33 Frühgeborenen ≤ 32+0 SSW täglich die Weaningentscheidungen, die NIV Parameter und Dauer sowie die Länge des Krankenhausaufenthaltes evaluiert. Zum Vergleich wurden retrospektive Daten von 33 nach Alter und Geschlecht angepassten Kindern, die vor 2017 betreut wurden, herangezogen. Um die Interater Reliabilität zu untersuchen, wurden SAS Scores, die von zwei verblindeten Untersuchern zu Videoaufnehmen vergeben wurden, mit entsprechenden Scores der Pflegekraft verglichen. Ergebnisse: Die Integration des SAS in unsere klinische Routine hatte geringen Einfluss auf die Weaningentscheidungen im Team. Entsprechend sahen wir keine Unterschiede in der NIV Dauer und der Länge des Krankenhausaufenthaltes im Vergleich zur Kontrollgruppe. An 30% der evaluierten Patiententage wurde die Beatmung nicht reduziert, trotz fehlender oder geringer Zeichen von Atemnot bzw. Atemarbeit (SAS ≤ 2). Hauptgrund für ein verzögertes Weaning waren Bradykardien (59% der Tage ohne Weaning), welche isoliert (40%) oder in Kombination mit anderen Faktoren, v.a. Desaturationen, auftraten. Darüber hinaus spielten aber auch sog. soft factors eine Rolle. Extreme Frühgeborene wurden bei vergleichbarem korrigierten Gestationsalter und niedrigem SAS zurückhaltender geweant als moderate Frühgeborene. Die Interrater Reliabilität war niedrig, unabhängig von der klinischen Erfahrung des Untersuchers (Fleiss' Kappa: 0.18). Diskussion: Der Weaningprozess wird von vielen Faktoren beeinflusst, wobei insbesondere das Auftreten von Bradykardien häufig zu einer Entscheidung gegen eine Reduktion der Beatmung führt trotz niedriger SAS-Werte. Während der SAS hilfreich ist, um die Notwendigkeit einer Atemunterstützung vorherzusagen, besitzt er bei der Beatmungsentwöhnung einen geringenprädiktiven Wert. Im Hinblick auf die möglichen negativen Konsequenzen einer unnötig langen Beatmung, muss die Relevanz isolierter Bradykardien für das Outcome infrage gestellt und näher untersucht werden. Die Integration weiterer Faktoren wie die Quantität und Qualität von Apnoen und Bradykardien in den Score könnte helfen, den Weaningprozess zu objektivieren und ggf. die NIV Dauer zu verkürzen. Entscheidend ist hierbei auch eine regelmäßige Schulung des Teams, um die Reliabilität des Scores zu verbessern

Noninvasive Ventilation in Preterm Infants: Factors Influencing Weaning Decisions and the Role of the Silverman-Andersen Score

The factors influencing weaning of preterm infants from noninvasive ventilation (NIV) are poorly defined and the weaning decisions are often driven by subjective judgement rather than objective measures. To standardize quantification of respiratory effort, the Silverman-Andersen Score (SAS) was included in our nursing routine. We investigated the factors that steer the weaning process and whether the inclusion of the SAS would lead to more stringent weaning. Following SAS implementation, we prospectively evaluated 33 neonates born <= 32 + 0 weeks gestational age. Age-, weight- and sex-matched infants born before routine SAS evaluation served as historic control. In 173 of 575 patient days, NIV was not weaned despite little respiratory distress (SAS <= 2), mainly due to bradycardias (60% of days without weaning), occurring alone (40%) or in combination with other factors such as apnea/desaturations. In addition, soft factors that are harder to grasp impact on weaning decisions, whereas the SAS overall played a minor role. Consequently, ventilation times did not differ between the groups. In conclusion, NIV weaning is influenced by various factors that override the absence of respiratory distress limiting the predictive value of the SAS. An awareness of the factors that influence weaning decisions is important as prolonged use of NIV has been associated with adverse outcome. Guidelines are necessary to standardize NIV weaning practice

Lipid Doppelschicht Stabilität unter hoher adhesiver Last

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersThe plasma membrane is the outermost component of cellular structures and as such it protects the cell interior from the external environment. Due to its wide range of biochemical functionality, the composition of this lipid bilayer structure is extremely complex and also differs from cell to cell. Supported lipid bilayers (SLBs) are greatly simplified model system for the plasma membrane and enable one to investigate the very basic properties of lipid bilayer structures. Due to the underlying substrate, the applicability of a variety of measurement techniques on the system is considerably enhanced. In this research, the stability of such synthetic lipid bilayer systems under high adhesion was investigated. For this purpose, the surface forces apparatus (SFA) was applied, yielding the distance-dependent interaction force of the deposited layer with an opposite surface and a qualitative measure of its mechanical compressibility. Time-stability and resistance of the systems to high adhesion forces could be detected by comparing sequential measurements performed on the same sample. In addition, the obtained data could be compared to the expected distance dependence of the interaction force according to DLVO theory. Atomic force microscopy (AFM) was further applied to measure the surface topographies of the systems which were then related to the results obtained from SFA experiments. The first measurements were performed on a mica supported 1,2-dipalmitoyl-snglycero-3-phosphocholine (DPPC) bilayer as a typical SLB system which was later modified in order to gain system stability. It was found that by introducing an inner layer with stronger interaction with the substrate material, a higher mechanical stability of the deposited layer structure under pressure could be achieved. This was shown for 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP) as the inner layer, giving an electrostatic attraction to the substrate, and, to a greater extent, for a self-assembled monolayer (SAM) of hexadecanethiol on gold as the inner layer, yielding a strong covalent bond to the substrate.5

Imagerie plein champ super-résolue basée sur un signal de fluorescence modulé dans le temps

La microscopie de fluorescence est actuellement la principale modalité d'imagerie appliquée en biologie cellulaire et moléculaire. Une méthode importante est SMLM (Single Molecule Localization Microscopy), qui permet la localisation de molécules individuelles dans des structures biologiques avec une précision nanométrique. Dans cette thèse, une nouvelle technique de microscopie de fluorescence est introduite, appelée TimeLoc (Time-modluation Localization Microscopy). Basé sur un motif de franges lumineuses d'excitation modulées dans le temps, il permet la localisation à grand champ d'émetteurs uniques en utilisant un module de comptage de photons unique comme dispositif de détection. En raison des taux d'acquisition élevés de ces modules, cela donne une augmentation considérable de la résolution temporelle par rapport aux techniques conventionnelles basées sur une caméra. La première partie de ce travail a consisté à mettre en œuvre cette nouvelle méthode, d'abord pour la localisation dans une puis dans les deux dimensions latérales. Une fois la configuration optique terminée, elle a d’abord été testée sur des billes fluorescentes de 40 nm, où les résultats expérimentaux ont montré un bon accord avec la limite théorique de précision de localisation de la technique. La configuration a ensuite été appliquée au suivi de particules uniques, où il a pu être démontré que cette méthode permet effectivement une augmentation considérable de la résolution temporelle par rapport aux méthodes basées sur une caméra. Dans la dernière partie de ce travail, TimeLoc a été combiné avec SMLM pour imager des structures biologiques. Les résultats préliminaires sur les microtubules marqués dans les cellules COS7 ont ainsi donné une preuve de concept pour l'application de TimeLoc sur SMLM.Fluorescence microscopy has emerged as the principal imaging modality applied in modern cell and molecular biology. A prominent method in the field is Single Molecule Localization Microscopy (SMLM), which allows the localization of individual molecules in biological structures at nanometric precision. In this doctorate thesis, a new fluorescence microscopy technique is introduced, which we named Time-modulation Localization microscopy (TimeLoc). Based on a time-modulated excitation light pattern of fringes, it enables wide-field localization of single emitters using a single photon counting module as a detection device. Due to the high acquisition rates of such modules, this gives a considerable increase in temporal resolution as compared to conventional camera-based techniques. The first part of this work consisted in implementing this new method, first for localization in one and then in both lateral dimensions. After completing the optical setup, it was first tested on 40 nm fluorescent beads, where experimental results showed good agreement with the technique’s theoretical limit of localization precision. The configuration was then applied on single particle tracking, where it could be shown that this method indeed allows for a considerable increase in temporal resolution as compared to camera-based methods. In the last part of this work, TimeLoc was combined with SMLM to image biological structures. Preliminary results on labelled microtubules in COS7 cells thereby gave a proof-of-concept for the application of TimeLoc on SMLM

Interaction Profiles and Stability of Rigid and Polymer-Tethered Lipid Bilayer Models at Highly Charged and Highly Adhesive Contacts

Preprint version of the article Bilotto, P., Lengauer, M., Andersson, J., Ramach, U., Mears, L. L. E., & Valtiner, M. (2019). Interaction Profiles and Stability of Rigid and Polymer-Tethered Lipid Bilayer Models at Highly Charged and Highly Adhesive Contacts. Langmuir, 35(48), 15552–15563. https://doi.org/10.1021/acs.langmuir.9b01942Understanding interaction force versus distance profiles of supported lipid bilayers (SLBs) is relevant to a number of areas, which rely on these model systems, including, e.g., characterization of ligand/receptor interactions or bacterial adhesion. Here, the stability of 4 different SLB architectures was compared using the surface forces apparatus (SFA) and atomic force microscopy (AFM). Specifically, the outer envelope of the bilayer systems remained constant as 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The inner layer was varied between DPPC and 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP) both on mica, and self-assembled monolayers (SAMs) of hexadecanethiol and the polymer-tethered diphytanylglycerol-tetraethylene glycol-lipoid acid (DPhyTL) on smooth gold surfaces. In that same order these gave an increasing strength of interaction between the inner layer and the supporting substrate and hence improved stability under highly adhesive conditions. Detachment profiles from highly charged and highly adhesive contacts were characterized, and approach characteristics were fitted to DLVO models. We find increasing stability under highly adhesive loads, approaching the hydrophobic limit of the adhesive energy between the inner and outer layers for the SAM-based systems. For all four SLBs we further compare AFM surface topographies, which strongly depend on preparation conditions, and the DLVO fitting of the SFA approach curves finds a strong charge regulation behavior during interaction, dependent on the particular model system. In addition, we find undulation characteristics during approach and separation. The increased stability of the complex architectures on a gold support makes these model systems an ideal starting point for studying more complex strongly adhesive/interacting systems, including, for example, ligand/receptor interactions, biosensing interactions, or cell/surface interactions.Europäischer Forschungsrat (ERC)

Noninvasive Ventilation in Preterm Infants: Factors Influencing Weaning Decisions and the Role of the Silverman-Andersen Score

The factors influencing weaning of preterm infants from noninvasive ventilation (NIV) are poorly defined and the weaning decisions are often driven by subjective judgement rather than objective measures. To standardize quantification of respiratory effort, the Silverman-Andersen Score (SAS) was included in our nursing routine. We investigated the factors that steer the weaning process and whether the inclusion of the SAS would lead to more stringent weaning. Following SAS implementation, we prospectively evaluated 33 neonates born &le; 32 + 0 weeks gestational age. Age-, weight- and sex-matched infants born before routine SAS evaluation served as historic control. In 173 of 575 patient days, NIV was not weaned despite little respiratory distress (SAS &le; 2), mainly due to bradycardias (60% of days without weaning), occurring alone (40%) or in combination with other factors such as apnea/desaturations. In addition, &ldquo;soft factors&rdquo; that are harder to grasp impact on weaning decisions, whereas the SAS overall played a minor role. Consequently, ventilation times did not differ between the groups. In conclusion, NIV weaning is influenced by various factors that override the absence of respiratory distress limiting the predictive value of the SAS. An awareness of the factors that influence weaning decisions is important as prolonged use of NIV has been associated with adverse outcome. Guidelines are necessary to standardize NIV weaning practice

Optimizing multiple beam interferometry in the surface forces apparatus: Novel optics, reflection mode modeling, metal layer thicknesses, birefringence, and rotation of anisotropic layers

Multiple beam interferometry (MBI) evolved as a powerful tool for the simultaneous evaluation of thin film thicknesses and refractive indices in Surface Forces Apparatus (SFA) measurements. However, analysis has relied on simplifications for providing fast or simplified analysis of recorded interference spectra. Here, we describe the implementation of new optics and a generalized fitting approach to 4 × 4 transfer matrix method simulations for the SFA. Layers are described by dispersive complex refractive indices, thicknesses, and Euler angles that can be fitted, providing modeling for birefringent or colored layers. Normalization of data by incident light intensities is essential for the implementation of a fitting approach. Therefore, a modular optical system is described that can be retrofit to any existing SFA setup. Real-time normalization of spectra by white light is realized, alignment procedures are considerably simplified, and direct switching between transmission and reflection modes is possible. A numerical approach is introduced for constructing transfer matrices for birefringent materials. Full fitting of data to the simulation is implemented for arbitrary multilayered stacks used in SFA. This enables self-consistent fitting of mirror thicknesses, birefringence, and relative rotation of anisotropic layers (e.g., mica), evaluation of reflection and transmission mode spectra, and simultaneous fitting of thicknesses and refractive indices of media confined between two surfaces. In addition, a fast full spectral fitting method is implemented for providing a possible real-time analysis with up to 30 fps. We measure and analyze refractive indices of confined cyclohexane, the thickness of lipid bilayers, the thickness of metal layers, the relative rotation of birefringent materials, contact widths, as well as simultaneous fitting of both reflection and transmission mode spectra of typical interferometers. Our analyses suggest a number of best practices for conducting SFA and open MBI in an SFA for increasingly complex systems, including metamaterials, multilayered anisotropic layers, and chiral layers.Europäischer Forschungsrat (ERC)1