Structural Identification Through Monitoring, Modeling And Predictive Analysis Under Uncertainty

Bridges are critical components of highway networks, which provide mobility and economical vitality to a nation. Ensuring the safety and regular operation as well as accurate structural assessment of bridges is essential. Structural Identification (St-Id) can be utilized for better assessment of structures by integrating experimental and analytical technologies in support of decision-making. St-Id is defined as creating parametric or nonparametric models to characterize structural behavior based on structural health monitoring (SHM) data. In a recent study by the ASCE St-Id Committee, St-Id framework is given in six steps, including modeling, experimentation and ultimately decision making for estimating the performance and vulnerability of structural systems reliably through the improved simulations using monitoring data. In some St-Id applications, there can be challenges and considerations related to this six-step framework. For instance not all of the steps can be employed; thereby a subset of the six steps can be adapted for some cases based on the various limitations. In addition, each step has its own characteristics, challenges, and uncertainties due to the considerations such as time varying nature of civil structures, modeling and measurements. It is often discussed that even a calibrated model has limitations in fully representing an existing structure; therefore, a family of models may be well suited to represent the structure’s response and performance in a probabilistic manner. The principle objective of this dissertation is to investigate nonparametric and parametric St-Id approaches by considering uncertainties coming from different sources to better assess the structural condition for decision making. In the first part of the dissertation, a nonparametric StId approach is employed without the use of an analytical model. The new methodology, which is iv successfully demonstrated on both lab and real-life structures, can identify and locate the damage by tracking correlation coefficients between strain time histories and can locate the damage from the generated correlation matrices of different strain time histories. This methodology is found to be load independent, computationally efficient, easy to use, especially for handling large amounts of monitoring data, and capable of identifying the effectiveness of the maintenance. In the second part, a parametric St-Id approach is introduced by developing a family of models using Monte Carlo simulations and finite element analyses to explore the uncertainty effects on performance predictions in terms of load rating and structural reliability. The family of models is developed from a parent model, which is calibrated using monitoring data. In this dissertation, the calibration is carried out using artificial neural networks (ANNs) and the approach and results are demonstrated on a laboratory structure and a real-life movable bridge, where predictive analyses are carried out for performance decrease due to deterioration, damage, and traffic increase over time. In addition, a long-span bridge is investigated using the same approach when the bridge is retrofitted. The family of models for these structures is employed to determine the component and system reliability, as well as the load rating, with a distribution that incorporates various uncertainties that were defined and characterized. It is observed that the uncertainties play a considerable role even when compared to calibrated model-based predictions for reliability and load rating, especially when the structure is complex, deteriorated and aged, and subjected to variable environmental and operational conditions. It is recommended that a family-of-models approach is suitable for structures that have less redundancy, high operational importance, are deteriorated, and are performing under close capacity and demand level

Atrial Fibrillation Management in Acute Stroke Patients in Türkiye: Real-life Data from the NöroTek Study

Objective: Atrial fibrillation (AF) is the most common directly preventable cause of ischemic stroke. There is no dependable neurology-based data on the spectrum of stroke caused by AF in Turkiye. Within the scope of NoroTek-Turkiye (TR), hospital-based data on acute stroke patients with AF were collected to contribute to the creation of acute-stroke algorithms.Materials and Methods: On May 10, 2018 (World Stroke Awareness Day), 1,790 patients hospitalized at 87 neurology units in 30 health regions were prospectively evaluated. A total of 929 patients [859 acute ischemic stroke, 70 transient ischemic attack (TIA)] from this study were included in this analysis.Results: The rate of AF in patients hospitalized for ischemic stroke/TIA was 29.8%, of which 65% were known before stroke, 5% were paroxysmal, and 30% were diagnosed after hospital admission. The proportion of patients with AF who received "effective" treatment [international normalization ratio >= 2.0 warfarin or non-vitamin K antagonist oral anticoagulants (NOACs) at a guideline dose] was 25.3%, and, either no medication or only antiplatelet was used in 42.5% of the cases. The low dose rate was 50% in 42 patients who had a stroke while taking NOACs. Anticoagulant was prescribed to the patient at discharge at a rate of 94.6%; low molecular weight or unfractionated heparin was prescribed in 28.1%, warfarin in 32.5%, and NOACs in 31%. The dose was in the low category in 22% of the cases discharged with NOACs, and half of the cases, who received NOACs at admission, were discharged with the same drug.Conclusion: NoroTekTR revealed the high but expected frequency of AF in acute stroke in Turkiye, as well as the aspects that could be improved in the management of secondary prophylaxis. AF is found in approximately one-third of hospitalized acute stroke cases in Turkiye. Effective anticoagulant therapy was not used in three-quarters of acute stroke cases with known AF. In AF, heparin, warfarin, and NOACs are planned at a similar frequency (one-third) within the scope of stroke secondary prophylaxis, and the prescribed NOAC dose is subtherapeutic in a quarter of the cases. Non-medical and medical education appears necessary to prevent stroke caused by AF

Gastrostomy in hospitalized patients with acute stroke: "NoroTek" Turkey point prevalence study subgroup analysis

Objective: Nutritional status assessment, dysphagia evaluation and enteral feeding decision are important determinants of prognosis in acute neurovascular diseases. Materials and Methods: NöroTek is a point prevalence study conducted with the participation of 87 hospitals spread across all health sub regions of Turkey conducted on 10-May-2018 (World Stroke Awareness Day). A total of 972 hospitalized neurovascular patients [female: 53%, age: 69±14; acute ischemic stroke in 845; intracerebral hematoma (ICH) in 119 and post-resuscitation encephalopathy (PRE) in 8] with complete data were included in this sub-study. Results: Gastrostomy was inserted in 10.7% of the patients with ischemic stroke, 10.1% of the patients with ICH and in 50% of the patients with PRE. Independent predictors of percutaneous endoscopic gastrostomy (PEG) administration were The National Institutes of Health Stroke Scale score at admission [exp (β): 1.09 95% confidence interval (CI): 1.05-1.14, per point] in ischemic stroke; and mechanical ventilation in ischemic [exp (β): 6.18 (95% CI: 3.16-12.09)] and hemorrhagic strokes [exp (β): 26.48 (95% CI: 1.36-515.8)]. PEG was found to be a significant negative indicator of favorable (modified Rankin’s scale score 0-2) functional outcome [exp (β): 0.032 (95% CI: 0.004-0.251)] but not of in-hospital mortality [exp (β): 1.731 (95% CI: 0.785-3.829)]. Nutritional and swallowing assessments were performed in approximately two-thirds of patients. Of the nutritional assessments 69% and 76% of dysphagia assessments were completed within the first 2 days. Tube feeding was performed in 39% of the patients. In 83.5% of them, tube was inserted in the first 2 days; 28% of the patients with feeding tube had PEG later. Conclusion: The NöroTek study provided the first reliable and large-scale data on key quality metrics of nutrition practice in acute stroke in Turkey. In terms of being economical and accurate it makes sense to use the point prevalence method.Amaç: Akut nörovasküler hastalıklarda nütrisyonel durum ve disfaji değerlendirmesi ve enteral beslenme kararı önemli prognoz belirleyicilerindendir. Gereç ve Yöntem: NöroTek, 10 Mayıs 2018’de (Dünya İnme Farkındalık Günü) Türkiye’nin tüm sağlık alt bölgelerine yayılmış 87 hastanenin katılımıyla gerçekleştirilen bir nokta prevalans çalışmasıdır. Hastanede yatan ve bu alt çalışma için toplanan verisi tam olan toplam 972 nörovasküler hasta (kadın: %53, yaş: 69±14 yıl; 845’i akut iskemik inme; 119’u intraserebral hematom ve 8’i post-resüsitasyon ensefalopatisi) analiz edildi. Bulgular: Gastrostomi iskemik inmeli hastaların %10,7, intraserebral kanamalıların %10,1 ve post-resusitasyon ensefalopatisi olanların %50’sine uygulanmıştır. Perkütan endoskopik gastrostomi (PEG) gereksiniminin bağımsız belirleyicileri, iskemik inme grubunda kabul NIHSS [exp (β): 1,09, %95 güven aralığı (GA): 1,05-1,14, puan başına] ile hem iskemik hem de hemorajik inmelerde mekanik ventilasyon uygulanmış olmasıdır [iskemik için: exp (β): 6,18, %95 GA: 3,16- 12,09] ve hemorajik inme için: [exp (β): 26,48, 95% GA: 1,36-515,8]. İnme olgularında PEG uygulaması hastane içi mortalite için bağımsız belirleyici değildi [exp (β): 1,731, 95% GA: 0,785-3,829]. Ancak, PEG uygulanmış olması taburculuk esnasında iyi prognoza (modifiye Rankin skoru 0-2) sahip olabilme için anlamlı bir negatif etmen olarak bulundu [exp (β): 0,032, %95 GA: 0,004-0,251]. Hastanede yatan nörovasküler hastaların yaklaşık üçte ikisinde malnütrisyon ve yutma bozukluğu açısından değerlendirme yapılmıştı. Nutrisyonel status değerlendirmesinin %69’u ve disfaji değerlendirmesinin %76’sı ilk 48 saat içinde gerçekleştirilmişti. Tüple enteral nütrisyon uygulama oranı %39’du. Beslenme tüplerinin %83,5’i ilk 2 gün içinde yerleştirilirken beslenme tüpü olan hastaların %28’ine daha sonra PEG açılmıştı. Sonuç: NöroTek çalışması ile Türkiye’de hastanede yatan akut inme hastalarında nutrisyonel uygulamaların temel kalite ölçütlerine ilişkin ilk güvenilir ve büyük ölçekli veri sağlanmıştır. Ekonomik olması ve doğruluğu açısından nokta yaygınlık yönteminin bu tip verilerin temini için daha fazla kullanılması mantıklıdır

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research