386 research outputs found
SKION: Digitale Basiskaart - Eindverslag
No full textThis document gives an overview of the progress and achievements of R. Spliet and S. Smit during their internship at SKION, including all delivered documentation.IN3405 BachelorprojectComputer ScienceElectrical Engineering, Mathematics and Computer Scienc
Diagnostic accuracy of lung ultrasound in diagnosis of ARDS and identification of focal or non-focal ARDS subphenotypes: a systematic review and meta-analysis
No full textBackgroundAcute respiratory distress syndrome (ARDS) is a life-threatening respiratory condition with high mortality rates, accounting for 10% of all intensive care unit admissions. Lung ultrasound (LUS) as diagnostic tool for acute respiratory failure has garnered widespread recognition and was recently incorporated into the updated definitions of ARDS. This raised the hypothesis that LUS is a reliable method for diagnosing ARDS.ObjectivesWe aimed to establish the accuracy of LUS for ARDS diagnosis and classification of focal versus non-focal ARDS subphenotypes.MethodsThis systematic review and meta-analysis used a systematic search strategy, which was applied to PubMed, EMBASE and cochrane databases. Studies investigating the diagnostic accuracy of LUS compared to thoracic CT or chest radiography (CXR) in ARDS diagnosis or focal versus non-focal subphenotypes in adult patients were included. Quality of studies was evaluated using the QUADAS-2 tool. Statistical analyses were performed using "Mada" in Rstudio, version 4.0.3. Sensitivity and specificity with 95% confidence interval of each separate study were summarized in a Forest plot.ResultsThe search resulted in 2648 unique records. After selection, 11 reports were included, involving 2075 patients and 598 ARDS cases (29%). Nine studies reported on ARDS diagnosis and two reported on focal versus non-focal ARDS subphenotypes classification. Meta-analysis showed a pooled sensitivity of 0.631 (95% CI 0.450-0.782) and pooled specificity of 0.942 (95% CI 0.856-0.978) of LUS for ARDS diagnosis. In two studies, LUS could accurately differentiate between focal versus non-focal ARDS subphenotypes. Insufficient data was available to perform a meta-analysis.ConclusionThis review confirms the hypothesis that LUS is a reliable method for diagnosing ARDS in adult patients. For the classification of focal or non-focal subphenotypes, LUS showed promising results, but more research is needed
Quantitative CT-analysis of over aerated lung tissue and correlation with fibrosis extent in patients with idiopathic pulmonary fibrosis.
No full textINTRODUCTION- The usual interstitial pneumonia (UIP) pattern, hallmark of idiopathic pulmonary fibrosis (IPF), may induce harmful local overdistension during mechanical ventilation given the juxtaposition of different tissue elasticities. Mechanotransduction, linking mechanical stress and strain to molecular pro-fibrotic pathways, likely contributes to fibrosis progression. Understanding the mechanical forces and aeration patterns in the lungs of IPF patients is crucial for unraveling potential mechanisms of disease progression. Quantitative lung computed tomography (CT) can accurately assess the air content of lung regions, thus informing on zonal distension. This study aims to investigate radiological evidence of lung over aeration in spontaneously breathing UIP patients compared to healthy controls during maximal inspiration.
METHODS- Patients with IPF diagnosis referred to the Center for Rare Lung Diseases of the University Hospital of Modena (Italy) in the period 2020-2023 who underwent High Resolution Computed Tomography (HRCT) scans at residual volume (RV) and total lung capacity (TLC) using standardized protocols were retrospectively considered eligible. Patients with no signs of lung disease at HRCT performed with the same image acquisition protocol nor at pulmonary function test (PFTs) served as controls. Lung segmentation and quantitative analysis were performed using 3D Slicer software. Lung volumes were measured, and specific density thresholds defined over aerated and fibrotic regions. Comparison between over aerated lung at RV and TLC in the two groups and according to lung lobes was sought. Further, the correlation between aerated lung and the extent of fibrosis was assessed and compared at RV and TLC.
RESULTS- IPF patients (N=20) exhibited higher over aerated lung proportions than controls (N=15) both at RV and TLC (4.5% vs. 0.7%, p<0.0001 and 13.8% vs. 7%, p<0.0001 respectively). Over aeration increased significantly from RV to TLC in both groups, with no intergroup difference (p=0.67). Sensitivity analysis revealed significant variations in over aerated lung areas among lobes when passing from RV to TLC with no difference within lobes (p=0.28). Correlation between over aeration and fibrosis extent was moderate at RV (r=0.62, p<0.0001) and weak at TLC (r=0.27, p=0.01), being the two significantly different at interpolation analysis (p<0.0001).
CONCLUSIONS-This study provides the first evidence of radiological signs of lung over aeration in patients with UIP-pattern patients when passing from RV to TLC. These findings offer new insights into the complex interplay between mechanical forces, lung structure, and fibrosis and warrant larger and longitudinal investigations
Design of ankle-knee prostheses using predictive simulations
No full textThere is an increasing need for transfemoral prostheses that provide gait support, stability, safety and comfort. Although there are many prostheses available in different levels of complexity and price, there is still room for improvement. It has been proved that the cost of transport (CoT) for walking is significantly increased for transfemoral amputees with respect to their healthy peers. Assisting push-off is one of the main challenges in prosthesis design. Push-off is normally achieved by plantarflexion of the ankle joint. Prosthesis designs should aim to restore this function in order to lower the amount of energy needed for walking. This study aims to investigate the effect of prosthesis design on the gait pattern through musculoskeletal modelling and predictive simulations. Two prosthesis designs are modelled for these purposes, after which several variations on these models are made. It is hypothesised that the prosthesis that assists in push-off through ankle plantarflexion, should result in a gait pattern that is closer to a healthy one. It should also decrease the CoT. Furthermore, we aim to evaluate the use of modelling and simulations in the customisation of prostheses.OpenSim was used to create a total of eight models based on a model with 9 degrees of freedom and 18 muscles: a healthy person, a conventional prosthesis model, two scaled versions of the conventional prosthesis model, the walkMECH prosthesis and three variations on the walkMECH. SCONE was used to find an optimal gait pattern for each of the models through the CMA-ES method. CoT-, gait-, degrees of freedom- and reaction force objectives were minimised. The results were evaluated by comparing the CoT, joint angles, ground reaction forces and muscle activation of each model.The CoT for the healthy model was found to be higher than reported before, based on both experimental and simulation studies. As a result, we have little confidence in the CoT estimation of our models. This is further exacerbated by the finding of a lower CoT for the conventional prosthesis than for the healthy model, in contrast to earlier reports. The results for most other measures were irregular, making it difficult to draw conclusions from them. It is expected that the predictive optimisations did not reach a global minimum, and that the results are therefore not accurate. Future research should aim to solve this problem. It should also be attempted to find the cause of the difference in CoT between our simulations and those of others.No conclusions could be drawn from the results. Nonetheless, there is a clear potential for the use of musculoskeletal modelling and predictive simulation in the investigation of the effects of prosthesis design on gait.Biomedical Engineerin
Validation of New Quantitative Lung Ultrasound Protocol and Comparison With Lung Ultrasound Score in Patients With COVID-19
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Thermal and Electrical Properties of Nanocomposites, Including Material Properties
No full textThe research described in this thesis is part of a state-funded IOP-EMVT project in cooperation with industrial companies, aiming at the design, assessment and implementation of new, environmental friendly (e.g. oil and SF6 - free) solid dielectric materials. A large disadvantage of solid polymer dielectrics is their relatively low thermal conductivity. Therefore, the focus in this thesis is on if and how nanotechnology can improve the thermal conductivity without deteriorating existing electrical properties. Epoxy resin, which is very common polymer material in the electrical and power industry, has been used as a host to create new insulating materials: nanocomposites. In order to improve the thermal conductivity of epoxy resin, thermally conducting but electrically insulating nanofillers, such as aluminum and magnesium oxides (Al2O3 and MgO), silicon dioxide (SiO2), boron and aluminum nitrides (BN and AlN) were used to dope the polymer matrix. Good compatibility and adhesion was achieved by surface modification of the nanoparticles, using a silane coupling agent. Proper dispersion of nanoparticles is a vital factor for the final properties of nanocomposites. Good and stable dispersion of nanoparticles in polymer matrices have been achieved by mechanical mixing and ultrasonic vibration. The quality of the dispersion of nanoparticles was satisfactory for most of the nanocomposite samples. The fabricated composites were classified into three types, according to the average particle size and the extent of agglomerates observed inside the polymer matrix. Dielectric spectroscopy revealed that the relative permittivity of many nanocomposites is lower than that of the pure epoxy. This surprises, since the relative permittivity of the bulk materials of the fillers used is higher than that of the epoxy. The anomalous dielectric behaviour of nanocomposites was explained by the existence of an interface layer between polymer matrix and inorganic filler, and its influence on the macroscopic properties of the composite. The dielectric spectroscopy investigations demonstrated a reduction of the real and imaginary parts of the complex permittivity for all samples after subjecting the samples to postcuring. The postcuring process leads to evaporation of absorbed water and finalizes the process of epoxy curing. It was postulated that the interface polymer volume, which is affected by the alignment of polymer chains around surface treated nanoparticles, conducts the heat much better than an amorphous polymer that is not altered by nanoparticles. We proposed a three-phase Lewis-Nielsen model to fit the thermal conductivity behaviour of nanocomposites, which have a third phase of aligned polymer layers. The model fits the experimental data very well and takes the thermal resistance of the interface into account. Besides the interfacial layer and its nature, the size of the particles, their aspect ratio, crystal structure and alignment inside the polymer as well as surface modification are important aspects in determining the thermal conductivity of composites. Several ways are proposed to optimize the nanocomposite processing to enable scaling up to large industrial volumes. Finally, possible harmful effects of nanoparticles on health and required precautions for the workplace are discussed in the course of this thesis.High Voltage Technology & ManagenmentElectrical Engineering, Mathematics and Computer Scienc
Stress-strain curve and elastic behavior of the fibrotic lung with usual interstitial pneumonia pattern during protective mechanical ventilation
No full textBackground- Patients with acute exacerbation of lung fibrosis with usual interstitial pneumonia (EUIP) pattern are at increased risk for ventilator-induced lung injury (VILI) and mortality when exposed to mechanical ventilation (MV). Yet, lack of a mechanical model describing UIP-lung deformation during MV represents a research gap. Aim of this study was to develop a constitutive mathematical model for UIP-lung deformation during lung protective MV based on the stress-strain behavior and the specific elastance of patients with EUIP as compared to that of acute respiratory distress syndrome (ARDS) and healthy lung.
Methods- Partitioned lung and chest wall mechanics were assessed for patients with EUIP and primary ARDS (1:1 matched based on body mass index and PaO2/FiO2 ratio) during a PEEP trial performed within 24 h from intubation. Patient’s stress-strain curve and the lung specific elastance were computed and compared with those of healthy lungs, derived from literature. Respiratory mechanics were used to fit a novel mathematical model of the lung describing mechanical-inflation-induced lung parenchyma deformation, differentiating the contributions of elastin and collagen, the main components of lung extracellular matrix.
Results- Five patients with EUIP and 5 matched with primary ARDS were included and analyzed. Global strain was not different at low PEEP between the groups. Overall specific elastance was significantly higher in EUIP as compared to ARDS (28.9 [22.8 – 33.2] cmH2O versus 11.4 [10.3 – 14.6] cmH2O, respectively). Compared to ARDS and healthy lung, the stress/strain curve of EUIP showed a steeper increase, crossing the VILI threshold stress risk for strain values greater than 0.55. The contribution of elastin was prevalent at lower strains, while the contribution of collagen was prevalent at large strains. The stress/strain curve for collagen showed an upward shift passing from ARDS and healthy lungs to EUIP lungs.
Conclusions- During MV, patients with EUIP showed different respiratory mechanics, stress-strain curve and specific elastance as compared to ARDS patients and healthy subjects and may experience VILI even when protective MV is applied. According to our mathematical model of lung deformation during mechanical inflation, the elastic response of UIP-lung is peculiar and different from ARDS. Our data suggest that patients with EUIP experience VILI with ventilatory setting that are lung-protective for patients with ARDS
Space charge accumulation in polymeric high voltage DC cable systems
No full textOne of the intrinsic properties of the polymeric high voltage (HV) direct current (DC) cable insulation is the accumulation of electrostatic charges. Accumulated charges distort the initial Laplacian distribution of the electric field, leading to a local field enhancement that may cause insulation degradation and premature breakdown of the system. The general objective of the present study is to obtain a better understanding of the major factors that control the space charge processes in polymeric HVDC cable systems. In order to achieve this goal, two main factors of influence have been investigated. 1) Cable accessories, i.e. cable joints and cable terminations, are considered to be the weakest part of a cable system, because of the presence of a dielectric interface between the cable insulation and that of the accessory. This thesis aims at a better knowledge of the polarization phenomena occurring at dielectric interfaces. To that purpose, an accurate methodology has been developed for the experimental study of the space charge behavior at the dielectric interface. The pulsed electro-acoustic (PEA) method for the measurement of space charge has been reviewed in case of dielectric interfaces. Secondly, space charge accumulation has been experimentally observed at the dielectric interfaces of different test specimens. 2) Across the insulation of HVDC cable systems a temperature drop is present when the cable carries a current. This thesis aims to provide a better understanding about the mechanisms responsible for space charge accumulation when a temperature drop is present across the insulation of the cable system. To that purpose, a physical model has been developed for the prediction of space charge dynamics and electric field in loaded HVDC cable systems. The physical model has been validated by means of laboratory investigation.Electrical Engineering, Mathematics and Computer Scienc
Modelling of the thermal conductivity in polymer nanocomposites and the impact of the interface between filler and matrix
No full textIn this paper the thermal conductivity of epoxy-based composite materials is analysed. Two and three-phase Lewis–Nielsen models are proposed for fitting the experimental values of the thermal conductivity of epoxy-based polymer composites. Various inorganic nano- and microparticles were used, namely aluminium oxide, aluminium nitride, magnesium oxide and silicon dioxide with average particle size between 20 nm and 20?m. It is shown that the filler–matrix interface plays a dominant role in the thermal conduction process of the nanocomposites. The two-phase model was proposed as an initial step for describing systems containing 2 constituents, i.e. an epoxy matrix and an inorganic filler. The three-phase model was introduced to specifically address the properties of the interfacial zone between the host polymer and the surface modified nanoparticles.Electrical Sustainable EnergyElectrical Engineering, Mathematics and Computer Scienc
The diagnostic accuracy for ARDS of global versus regional lung ultrasound scores - a post hoc analysis of an observational study in invasively ventilated ICU patients
No full textBackground
Semi-quantification of lung aeration by ultrasound helps to assess presence and extent of pulmonary pathologies, including the acute respiratory distress syndrome (ARDS). It is uncertain which lung regions add most to the diagnostic accuracy for ARDS of the frequently used global lung ultrasound (LUS) score. We aimed to compare the diagnostic accuracy of the global versus those of regional LUS scores in invasively ventilated intensive care unit patients.
Methods
This was a post-hoc analysis of a single-center observational study in the mixed medical–surgical intensive care unit of a university-affiliated hospital in the Netherlands. Consecutive patients, aged ≥ 18 years, and are expected to receive invasive ventilation for > 24 h underwent a LUS examination within the first 2 days of ventilation. The Berlin Definition was used to diagnose ARDS, and to classify ARDS severity. From the 12-region LUS examinations, the global score (minimum 0 to maximum 36) and 3 regional scores (the ‘anterior,’ ‘lateral,’ and ‘posterior’ score, minimum 0 to maximum 12) were computed. The area under the receiver operating characteristic (AUROC) curve was calculated and the best cutoff for ARDS discrimination was determined for all scores.
Results
The study enrolled 152 patients; 35 patients had ARDS. The global score was higher in patients with ARDS compared to patients without ARDS (median 19 [15–23] vs. 5 [3–9]; P Conclusions
While the posterior score increases with ARDS severity, its diagnostic accuracy for ARDS is hampered due to an unfavorable signal-to-noise ratio. An 8-region ‘anterolateral’ score performs as well as the global score and may prove useful to exclude ARDS in invasively ventilated ICU patients
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