Bayesian calibration of flood inundation simulators using an observation of flood extent

Abstract We develop a Bayesian framework for calibrating flood inundation simulators Oll an observation of flood extent. and making calibrated predictions of a future event. We illustrate the framework using the binary channel (BC) model for the likelihood of the observed flood extent given a simulation of flood extent.. The BC model leads to poor results, and this motivates the search for a more appropriate likelihood model, which forms the basis for the rest of the thesis. We extend the Ising model to regression on a binary image and review methods for dealing with the intractable normalising constant. We propose novel applications of path sampling. extend path sampling to sampling over areas, and develop approximations to path sampling. We also develop the heterogeneous binary channel (HBC) model to test the effect of heterogeneity and spatial dependence. We extend the hidden conditional autoregressive (HCAR) model to regression on a binary image. We show that the limit of the HCAR model as the parameters approach the boundary is the (improper) hidden intrinsic autoregressive (HIAR) model. We prove that the HIAR model can be used for calibration but not calibrated prediction. We develop a number of methods for improving mixing of the MCMC algorithm. We explore two extensions of the HCAR model. First the heterogeneous HCAR (HHCAR) model, which represents heterogeneity, and second the continuous HCAR (CHCAR) model, which uses continuous simulation values. In conclusion, using our Bayesian framework we can replicate the results of less rigorous approaches. for example generalised likelihood uncertainty estimation (GLUE), and make probabilistic predictions which are not possible in these less rigorous approaches. Future work would further develop the likelihood models.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Large-Scale Educational Question Analysis with Partial Variational Auto-encoders

Online education platforms enable teachers to share a large number of educational resources such as questions to form exercises and quizzes for students. With large volumes of such crowd-sourced questions, quantifying the properties of these questions in crowd-sourced online education platforms is of great importance to enable both teachers and students to find high-quality and suitable resources. In this work, we propose a framework for large-scale question analysis. We utilize the state-of-the-art Bayesian deep learning method, in particular partial variational auto-encoders, to analyze real-world educational data. We also develop novel objectives to quantify question quality and difficulty. We apply our proposed framework to a real-world cohort with millions of question-answer pairs from an online education platform. Our framework not only demonstrates promising results in terms of statistical metrics but also obtains highly consistent results with domain expert evaluation.Comment: 19 pages, 13 figure

Mental health of UK military personnel while on deployment in Iraq

Background Most research on the mental health of UK armed forces personnel has been conducted either before or after deployment; there is scant evidence concerning personnel while they are on deployment. Aims To assess the mental health of UK armed forces personnel deployed in Iraq and identify gaps in the provision of support on operations. Method Personnel completed a questionnaire about their deployment experiences and health status. Primary outcomes were psychological distress (General Health Questionnaire–12, GHQ–12), symptoms of post-traumatic stress disorder (PTSD) and self-rating of overall health. Results Of 611 participants, 20.5% scored above the cut-off on the GHQ–12 and 3.4% scored as having probable PTSD. Higher risk of psychological distress was associated with younger age, female gender, weaker unit cohesion, poorer perceived leadership and non-receipt of a pre-deployment stress brief. Perceived threat to life, poorer perceived leadership and non-receipt of a stress brief were risk factors for symptoms of PTSD. Better self-rated overall health was associated with being a commissioned officer, stronger unit cohesion and having taken a period of rest and recuperation. Personnel who reported sick for any reason during deployment were more likely to report psychological symptoms. Around 11% reported currently being interested in receiving help for a psychological problem. Conclusions In an established operational theatre the prevalence of common psychopathology was similar to rates found in non-deployed military samples. However, there remains scope for further improving in-theatre support mechanisms, raising awareness of the link between reporting sick and mental health and ensuring implementation of current policy to deliver pre-deployment stress briefs

Procalcitonin guided antibiotic therapy and hospitalization in patients with lower respiratory tract infections: a prospective, multicenter, randomized controlled trial

<p>Abstract</p> <p>Background:</p> <p>Lower respiratory tract infections like acute bronchitis, exacerbated chronic obstructive pulmonary disease and community-acquired pneumonia are often unnecessarily treated with antibiotics, mainly because of physicians' difficulties to distinguish viral from bacterial cause and to estimate disease-severity. The goal of this trial is to compare medical outcomes, use of antibiotics and hospital resources in a strategy based on enforced evidence-based guidelines versus procalcitonin guided antibiotic therapy in patients with lower respiratory tract infections.</p> <p>Methods and design:</p> <p>We describe a prospective randomized controlled non-inferiority trial with an open intervention. We aim to randomize over a fixed recruitment period of 18 months a minimal number of 1002 patients from 6 hospitals in Switzerland. Patients must be >18 years of age with a lower respiratory tract infections <28 days of duration. Patients with no informed consent, not fluent in German, a previous hospital stay within 14 days, severe immunosuppression or chronic infection, intravenous drug use or a terminal condition are excluded. Randomization to either guidelines-enforced management or procalcitonin-guided antibiotic therapy is stratified by centre and type of lower respiratory tract infections. During hospitalization, all patients are reassessed at days 3, 5, 7 and at the day of discharge. After 30 and 180 days, structured phone interviews by blinded medical students are conducted. Depending on the randomization allocation, initiation and discontinuation of antibiotics is encouraged or discouraged based on evidence-based guidelines or procalcitonin cut off ranges, respectively. The primary endpoint is the risk of combined disease-specific failure after 30 days. Secondary outcomes are antibiotic exposure, side effects from antibiotics, rate and duration of hospitalization, time to clinical stability, disease activity scores and cost effectiveness. The study hypothesis is that procalcitonin-guidance is non-inferior (i.e., at worst a 7.5% higher combined failure rate) to the management with enforced guidelines, but is associated with a reduced total antibiotic use and length of hospital stay.</p> <p>Discussion:</p> <p>Use of and prolonged exposure to antibiotics in lower respiratory tract infections is high. The proposed trial investigates whether procalcitonin-guidance may safely reduce antibiotic consumption along with reductions in hospitalization costs and antibiotic resistance. It will additionally generate insights for improved prognostic assessment of patients with lower respiratory tract infections.</p> <p>Trial registration:</p> <p>ISRCTN95122877</p

Procalcitonin levels in acute exacerbation of COPD admitted in ICU: a prospective cohort study

<p>Abstract</p> <p>Background</p> <p>Antibiotics are recommended for severe acute exacerbation of chronic obstructive pulmonary disease (AECOPD) admitted to intensive care units (ICU). Serum procalcitonin (PCT) could be a useful tool for selecting patients with a lower probability of developing bacterial infection, but its measurement has not been investigated in this population.</p> <p>Methods</p> <p>We conducted a single center prospective cohort study in consecutive COPD patients admitted to the ICU for AECOPD between September 2005 and September 2006. Sputum samples or tracheal aspirates were tested for the presence of bacteria and viruses. PCT levels were measured at the time of admittance, six hours, and 24 hours using a sensitive immunoassay.</p> <p>Results</p> <p>Thirty nine AECOPD patients were included, 31 of which (79%) required a ventilator support at admission. The median [25%–75% interquartile range] PCT level, assessed in 35/39 patients, was: 0.096 μg/L [IQR, 0.065 to 0.178] at the time of admission, 0.113 μg/L [IQR, 0.074 to 0.548] at six hours, and 0.137 μg/L [IQR, 0.088 to 0.252] at 24 hours. The highest PCT (PCTmax) levels were less than 0.1 μg/L in 14/35 (40%) patients and more than 0.25 μg/L in 10/35 (29%) patients, suggesting low and high probability of bacterial infection, respectively. Five species of bacteria and nine species of viruses were detected in 12/39 (31%) patients. Among the four patients positive for <it>Pseudomonas aeruginosa</it>, one had a PCTmax less than 0.25 μg/L and three had a PCTmax less than 0.1 μg/L. The one patient positive for <it>Haemophilus influenzae </it>had a PCTmax more than 0.25 μg/L. The presence or absence of viruses did not influence PCT at time of admission (0.068 vs 0.098 μg/L respectively, <it>P </it>= 0.80).</p> <p>Conclusion</p> <p>The likelihood of bacterial infection is low among COPD patients admitted to ICU for AECOPD (40% with PCT < 0.1 μg/L) suggesting a possible inappropriate use of antibiotics. Further studies are necessary to assess the impact of a procalcitonin-based therapeutic strategy in critically ill COPD patients.</p

Outcome of Hospitalization for COVID-19 in Patients with Interstitial Lung Disease. An International Multicenter Study.

Rationale: The impact of coronavirus disease (COVID-19) on patients with interstitial lung disease (ILD) has not been established.Objectives: To assess outcomes in patients with ILD hospitalized for COVID-19 versus those without ILD in a contemporaneous age-, sex-, and comorbidity-matched population.Methods: An international multicenter audit of patients with a prior diagnosis of ILD admitted to the hospital with COVID-19 between March 1 and May 1, 2020, was undertaken and compared with patients without ILD, obtained from the ISARIC4C (International Severe Acute Respiratory and Emerging Infection Consortium Coronavirus Clinical Characterisation Consortium) cohort, admitted with COVID-19 over the same period. The primary outcome was survival. Secondary analysis distinguished idiopathic pulmonary fibrosis from non-idiopathic pulmonary fibrosis ILD and used lung function to determine the greatest risks of death.Measurements and Main Results: Data from 349 patients with ILD across Europe were included, of whom 161 were admitted to the hospital with laboratory or clinical evidence of COVID-19 and eligible for propensity score matching. Overall mortality was 49% (79/161) in patients with ILD with COVID-19. After matching, patients with ILD with COVID-19 had significantly poorer survival (hazard ratio [HR], 1.60; confidence interval, 1.17-2.18; P = 0.003) than age-, sex-, and comorbidity-matched controls without ILD. Patients with an FVC of <80% had an increased risk of death versus patients with FVC ≥80% (HR, 1.72; 1.05-2.83). Furthermore, obese patients with ILD had an elevated risk of death (HR, 2.27; 1.39-3.71).Conclusions: Patients with ILD are at increased risk of death from COVID-19, particularly those with poor lung function and obesity. Stringent precautions should be taken to avoid COVID-19 in patients with ILD

Effects of a respiratory physiotherapy session in patients with LRTI: a pre/post-test study

Introduction The role of respiratory physiotherapy (RP) in lower respiratory tract infections (LRTI) has been questioned. However, studies have focused on hospitalised patients, and the presence/absence of an underlying disease has been neglected. Objectives To assess the effects of a RP session in community patients with LRTI and to explore the differences between patients with pneumonia (restrictive disease – AR) and those with exacerbations of an obstructive disease (AO). Methods A pre/post-test study was conducted. A RP session was applied to patients with LRTI and crackles, wheezes, dyspnoea, perception of sputum and oxygen saturation were collected pre/post session. Comparisons were performed using paired t-tests or Wilcoxon tests. Results Thirty patients (14 males, 55.23 ± 17.78 years) with pneumonia (AR, n = 12), exacerbations of chronic obstructive pulmonary disease, acute bronchitis and asthma (AO, n = 18) were enrolled. After treatment, the total sample presented lower wheeze rates at trachea (P = 0.02; r = −0.54) and less sputum (P = 0.01; r = −0.47). AR patients presented a decrease in the number of crackles (P < 0.05; 0.30 < dz < 0.26) and number and rate of wheezes at chest locations (P < 0.05; −0.56 < r < −0.48). AO patients showed an increase in the number of crackles (P < 0.05; 0.20 <dz <0.31), wheeze frequency (P = 0.03; r = −0.27) and dyspnoea (P = 0.04; r = −0.55); and a decrease in the number of wheezes at trachea (P = 0.02; r = −0.54). Conclusions RP seems effective in reducing wheezes and perception of sputum in patients with LRTI. However, when considering AR and AO diseases separately, further changes in respiratory sounds and dyspnoea emerged. This highlights the importance of considering subgroups of patients with LRTI to develop RP evidence-base practice