Optimal design of boundary observers for the wave equation

In this article, we consider the wave equation on a domain of $\mathbb{R}^n$ with Lipschitz boundary. For every observable subset $\Gamma$ of the boundary $\partial\Omega$ the observability constant provides an account for the quality of the reconstruction in some inverse problem. Our objective is here to determine what is, in some appropriate sense, the best observation domain. After having defined a \textit{randomized observability constant}, more relevant tan the usual one in applications, we determine the optimal value of this constant over all possible subsets $\Gamma$ of prescribed measure $L|\partial\Omega|$, with $L\in(0,1)$, under appropriate spectral assumptions on $\Omega$. We compute the maximizers of a relaxed version of the problem, and then study the existence of an optimal set of particular domains $\Omega$. We then define and study an approximation of the problem with a finite number of modes, showing existence and uniqueness of an optimal set, and provide some numerical simulations

Inhaled corticosteroids and adverse outcomes among chronic obstructive pulmonary disease patients with community-acquired pneumonia: a population-based cohort study

IntroductionWhile inhaled corticosteroids (ICS) may increase pneumonia risk in patients with chronic obstructive pulmonary disease (COPD), the impact of ICS on pneumonia outcomes is debated. We examined whether ICS use is associated with adverse outcomes among COPD patients with community-acquired pneumonia (CAP).Materials and methodsPopulation-based cohort study of all COPD patients with an incident hospitalization for CAP between 1997 and 2013 in Northern Denmark. Information on medications, COPD severity, comorbidities, complications, and death was obtained from medical databases. Adjusted risk ratios (aRRs) for pleuropulmonary complications, intensive care unit (ICU) admissions, and 30-day mortality in current and former ICS users were compared with those in non-users, using regression analyzes to handle confounding.ResultsOf 11,368 COPD patients with CAP, 6,073 (53.4%) were current ICS users and 1,733 (15.2%) were former users. Current users had a non-significantly decreased risk of pleuropulmonary complications [2.6%; aRR = 0.82 (0.59–1.12)] compared to non-users (3.2%). This was also observed among former users [2.5%; aRR = 0.77 (0.53–1.12)]. Similarly, decreased risks of ICU admission were observed among current users [aRR = 0.77 (0.57–1.04)] and among former users [aRR = 0.81 (0.58–1.13)]. Current ICS users had significantly decreased 30-day mortality [9.1%; aRR = 0.72 (0.62–0.85)] compared to non-users (12.6%), with a stronger association observed among patients with frequent exacerbations [0.58 (0.39–0.86)]. No significant association was observed among former ICS users [0.89 (0.75–1.05)].ConclusionOur results suggest a decreased risk of death with ICS use among COPD patients admitted for CAP

Prognostic value of right ventricular dilatation on computed tomography pulmonary angiogram for predicting adverse clinical events in severe COVID-19 pneumonia

BackgroundRight ventricle dilatation (RVD) is a common complication of non-intubated COVID-19 pneumonia caused by pro-thrombotic pneumonitis, intra-pulmonary shunting, and pulmonary vascular dysfunction. In several pulmonary diseases, RVD is routinely measured on computed tomography pulmonary angiogram (CTPA) by the right ventricle-to-left ventricle (LV) diameter ratio > 1 for predicting adverse events.ObjectiveThe aim of the study was to evaluate the association between RVD and the occurrence of adverse events in a cohort of critically ill non-intubated COVID-19 patients.MethodsBetween February 2020 and February 2022, non-intubated patients admitted to the Amiens University Hospital intensive care unit for COVID-19 pneumonia with CTPA performed within 48 h of admission were included. RVD was defined by an RV/LV diameter ratio greater than one measured on CTPA. The primary outcome was the occurrence of an adverse event (renal replacement therapy, extracorporeal membrane oxygenation, 30-day mortality after ICU admission).ResultsAmong 181 patients, 62% (n = 112/181) presented RVD. The RV/LV ratio was 1.10 [1.05–1.18] in the RVD group and 0.88 [0.84–0.96] in the non-RVD group (p = 0.001). Adverse clinical events were 30% and identical in the two groups (p = 0.73). In Receiving operative curves (ROC) analysis, the RV/LV ratio measurement failed to identify patients with adverse events. On multivariable Cox analysis, RVD was not associated with adverse events to the contrary to chest tomography severity score > 10 (hazards ratio = 1.70, 95% CI [1.03–2.94]; p = 0.04) and cardiovascular component (> 2) of the SOFA score (HR = 2.93, 95% CI [1.44–5.95], p = 0.003).ConclusionRight ventricle (RV) dilatation assessed by RV/LV ratio was a common CTPA finding in non-intubated critical patients with COVID-19 pneumonia and was not associated with the occurrence of clinical adverse events

Admission of advanced lung cancer patients to intensive care unit: A retrospective study of 76 patients

<p>Abstract</p> <p>Background</p> <p>Criteria for admitting patients with incurable diseases to the medical intensive care unit (MICU) remain unclear and have ethical implications.</p> <p>Methods</p> <p>We retrospectively evaluated MICU outcomes and identified risk factors for MICU mortality in consecutive patients with advanced lung cancer admitted to two university-hospital MICUs in France between 1996 and 2006.</p> <p>Results</p> <p>Of 76 included patients, 49 had non-small cell lung cancer (stage IIIB n = 20; stage IV n = 29). In 60 patients, MICU admission was directly related to the lung cancer (complication of cancer management, n = 30; cancer progression, n = 14; and lung-cancer-induced diseases, n = 17). Mechanical ventilation was required during the MICU stay in 57 patients. Thirty-six (47.4%) patients died in the MICU. Three factors were independently associated with MICU mortality: use of vasoactive agents (odds ratio [OR] 6.81 95% confidence interval [95%CI] [1.77-26.26], p = 0.005), mechanical ventilation (OR 6.61 95%CI [1.44-30.5], p = 0.015) and thrombocytopenia (OR 5.13; 95%CI [1.17-22.5], p = 0.030). In contrast, mortality was lower in patients admitted for a complication of cancer management (OR 0.206; 95%CI [0.058-0.738], p = 0.015). Of the 27 patients who returned home, four received specific lung cancer treatment after the MICU stay.</p> <p>Conclusions</p> <p>Patients with acute complications of treatment for advanced lung cancer may benefit from MCIU admission. Further studies are necessary to assess outcomes such as quality of life after MICU discharge.</p

Optimal shape of boundary observation domains for the wave equation. Applications to photoacoustic tomography

On considère dans cette thèse l'équation des ondes posée sur un domaine Ω supposé régulier. Si Ω désigne une surface supposée observable, on peut définir la constante d'observabilité associée à Ω. L'intérêt de cette constante est de rendre compte de la qualité de la reconstruction dans le problème inverse qui consiste à reconstruire les données initiales à partir de la mesure de la solution sur Ω. Ainsi l'étude de cette constante s'applique entre autres à la détermination de la forme et du placement optimaux de capteurs, pour la mesure de toute sorte de phénomènes ondulatoires. Le but du premier chapitre est de caractériser de manière théorique les domaines Ω de surface prescrite qui maximisent cette constante d'observabilité, ou plus exactement une version "randomizée" de ce critère. Dans le second chapitre il s'agit d'appliquer les résultats obtenus au placement optimal de capteurs pour la tomographie photoacoustique. La tomographie photoacoustique est un procédé d'imagerie médicale ultra-sonore, non invasif encore peu développé qui est une alternative précise et plus économique à l'imagerie X. C'est dans ce cadre que l'on propose une modélisation de l'influence de la forme et de la disposition des capteurs dans le problème de reconstruction de la densité des tissus. Plus particulièrement, il s'agira de construire une fonctionnelle de la forme des capteurs, rendant compte de la qualité de l'image obtenue.In the first part of this thesis, we consider the wave equation on a regular bounded domain Ω. We investigate the problem of optimizing, in some appropriate sense, the shape and location of sensors spread on an arbitrary measurable subdomain Ω of the boundary of Ω. We introduce a spectral quantity called randomized observability constant, corresponding to the best constant in an average of the classical observability inequality, over random initial data. The pupose of the first chapter is to investigate optimal domains, maximizing the new objective function. The second part consists in applying the previous results to medical imaging, and more precisely to photoacoustic tomography. This imaging technique, constitutes a cutting-edge technology that has drawn considerable attention in the medical imaging area. Firstly because it is non-ionizing and non-invasive, and also because it constitutes a precise and cheap alternative to X imaging. In this framework, we propose here to model the influence of the shape and position of sensors in the inverse problem consisting in the reconstruction of the imaged body. In a nutshell, we build a functional of the shape of the sensors, providing an account for the reconstructed image quality

Optimisation de la forme des zones d'observation pour l'équation des ondes. Applications à la tomographie photoacoustique

In the first part of this thesis, we consider the wave equation on a regular bounded domain Ω. We investigate the problem of optimizing, in some appropriate sense, the shape and location of sensors spread on an arbitrary measurable subdomain Ω of the boundary of Ω. We introduce a spectral quantity called randomized observability constant, corresponding to the best constant in an average of the classical observability inequality, over random initial data. The pupose of the first chapter is to investigate optimal domains, maximizing the new objective function. The second part consists in applying the previous results to medical imaging, and more precisely to photoacoustic tomography. This imaging technique, constitutes a cutting-edge technology that has drawn considerable attention in the medical imaging area. Firstly because it is non-ionizing and non-invasive, and also because it constitutes a precise and cheap alternative to X imaging. In this framework, we propose here to model the influence of the shape and position of sensors in the inverse problem consisting in the reconstruction of the imaged body. In a nutshell, we build a functional of the shape of the sensors, providing an account for the reconstructed image quality.On considère dans cette thèse l'équation des ondes posée sur un domaine Ω supposé régulier. Si Ω désigne une surface supposée observable, on peut définir la constante d'observabilité associée à Ω. L'intérêt de cette constante est de rendre compte de la qualité de la reconstruction dans le problème inverse qui consiste à reconstruire les données initiales à partir de la mesure de la solution sur Ω. Ainsi l'étude de cette constante s'applique entre autres à la détermination de la forme et du placement optimaux de capteurs, pour la mesure de toute sorte de phénomènes ondulatoires. Le but du premier chapitre est de caractériser de manière théorique les domaines Ω de surface prescrite qui maximisent cette constante d'observabilité, ou plus exactement une version "randomizée" de ce critère. Dans le second chapitre il s'agit d'appliquer les résultats obtenus au placement optimal de capteurs pour la tomographie photoacoustique. La tomographie photoacoustique est un procédé d'imagerie médicale ultra-sonore, non invasif encore peu développé qui est une alternative précise et plus économique à l'imagerie X. C'est dans ce cadre que l'on propose une modélisation de l'influence de la forme et de la disposition des capteurs dans le problème de reconstruction de la densité des tissus. Plus particulièrement, il s'agira de construire une fonctionnelle de la forme des capteurs, rendant compte de la qualité de l'image obtenue

Le syndrome d'apnées obstructives du sommeil et chirurgie bariatrique par "sleeve gastrectomy" (données rétrospectives de 2004 à 2012 au centre hospitalier universitaire d'Amiens)

Introduction : L obésité (index de masse corporelle (IMC) supérieur à 30 kg/m2) est un risque reconnu de développer un syndrome d apnée obstructive du sommeil (SAOS). La chirurgie bariatrique par sleeve gastrectomy (SG) fait l objet de recommandations dans l obésité morbide ou en présence de co-morbidités. Les patients candidats à cette chirurgie bénéficient d une évaluation de l existence d un SAOS. L objet principal de notre étude était d étudier les différents critères clinico-biologiques et comorbidités cardiovasculaires associés au SAOS dans cette population de patients et secondairement les effets du SAOS sur la chirurgie, et de la chirurgie sur le SAOS après amaigrissement. Matériels et méthode : Il s agit d une étude monocentrique rétrospective de 2004 à 2012 sur 216 patients évalués au CHU d Amiens au laboratoire de pathologie du sommeil et de la vigilance, et suivi par l équipe de chirurgie viscérale et métabolique dans un projet de chirurgie bariatrique par SG. Résultats : Sur 216 patients 36 ont été diagnostiqués pour un SAOS et appareillés, qui étaient plus souvent des hommes (61,1% vs 41,5 p<0,01), avec un IMC significativement plus important (49,23kg/m2 dans le groupe SAOS vs 44,82 kg/m2 p<0,01) et un tour de cou significativement plus important corrélés à l IAH (47,92cm vs 42,35 p<0,01). Il existait une corrélation entre IMC et index d apnées-hypopnées (IAH). Sur les 36 patients SAOS, 24 d entre eux ont été opérés sans qu il soit observé d augmentation de complications per-opératoires ou post opératoires. Parmi ces patients, 17 ont pu être réévalués en polysomnographie après amaigrissement (IMC= 56,74kg/m2 pré opératoire vs 36,89kg/m2 post amaigrissement p<0,01), 15 patients ont été complètement désappareillés (IAH=56,74 vs 10,12p<0,01) avec amélioration significative des gaz du sang sur la pO2 et pCO2. Il est noté chez ces patients une amélioration significative de l architecture du sommeil. Conclusion : Notre étude a mis en évidence une corrélation entre IAH et IMC, tour de cou et tour de taille des patients SAOS. La chirurgie de l obésité par SG montre des résultats intéressant sur le SAOS via l amaigrissement obtenu avec l arrêt de l appareillage du SAOS, une amélioration de l architecture du sommeil et des paramètres gazométriques chez 15 de nos patients réévalués.Background: Obesity (a body mass index (BMI) over 30kg/m2) is a risk factor to develop sleep obstructive apnea syndrom (SOAS). Bariatric surgery with sleeve gastrectomy (SG) is well codified for morbid obese patients or for those with comorbidities. Patients eligible for surgery require evaluation of SOAS before surgery. The main objective of our study was to analyze clinical or biological risks factors associated with SOAS. Secondary objectives were to evaluate effects of SOAS on the bariatric surgery and on the other hand effects of batrictric surgery on SOAS improvement after weigth loss. Methods: This study is a retrospective study conducted from 2004 to 2012 on 216 patients evaluated in the sleep laboratory of Amiens. These patients were followed up for undergoing bariatric surgery with SG technique.Results: On these 216 patients, 36 were diagnosed for a SAS and were treated with continuous positive airway pressure (CPAP). A greater part of them were men (61.1% vs. 41.5 p<0.01), with a significant increase of BMI (49.23kg/m2 in SAS vs. 44.82 kg/m2 p<0.01), an increased of neck circumference (47.92 vs. 42.35 p<0.01). A correlation between BMI and Hypopnea-Apnea index (HAI) was found. Over the 36 patients diagnosed for SOAS, 24 of them underwent SG without an increase of complication rate. Among these 24 patients, 17 underwent a polysomnography after surgery and weight loss. (BMI= 56,74kg/m2 before surgery vs. 36,89kg/m2 after weight loss p<0.01), for 15 of them positive airway pressure had been stopped (HAI 56.74 vs. 10.12, p<0.01) with significant improvement of blood gas (pO2 and pCO2). A best quality of sleep had been observed. Conclusion: This study shows a correlation between HAI and BMI, neck circumference and waist circumference for SOAS patients. SG shows good results on SOAS, having allowed by weight loss a stop of CPAP, an improvement of sleep structure and blood gas on 15 patients.AMIENS-BU Santé (800212102) / SudocSudocFranceF

Optimal design of boundary observers for the wave equation

In this article, we consider the wave equation on a domain of Rn with Lipschitz boundary. For every observable subset Γ of the boundary ∂Ω (endowed with the usual Hausdorff measure Hn − 1 on ∂Ω), the observability constant provides an account for the quality of the reconstruction in some inverse problem. Our objective is here to determine what is, in some appropriate sense, the best observation domain. After having defined a randomized observability constant, more relevant tan the usual one in applications, we determine the optimal value of this constant over all possible subsets Γ of prescribed area Hn − 1(Γ) = LHn − 1(∂Ω), with L ∈ (0,1), under appropriate spectral assumptions on Ω. We compute the maximizers of a relaxed version of the problem, and then study the existence of an optimal set of particular domains Ω. We then define and study an approximation of the problem with a finite number of modes, showing existence and uniqueness of an optimal set, and provide some numerical simulations

Effects of nasal positive-pressure hyperventilation on the glottis in normal sleeping subjects.

We have previously observed that, in normal awake subjects passively hyperventilated with intermittent positive-pressure ventilation delivered through nasal access (nIPPV), the glottis could interfere with the ventilation. We report on data obtained in the same subjects during stable sleep. In all cases, the glottis was continuously observed through a fiber-optic bronchoscope, and other indexes were also continuously recorded. Mechanical ventilation was progressively increased up to 30 l/min. We have observed during passive nIPPV in stable sleep that increases in delivered minute ventilation (VEd) resulted in progressive narrowing of the glottic aperture, with increases in inspiratory resistance and progressive reductions in the percentage of the delivered tidal volume effectively reaching the lungs. For a given level of VEd, comparisons showed that the glottis was significantly narrower during sleep than during wakefulness and that the glottis was significantly narrower during stage 2 than during stages 3/4 non-rapid-eye-movement sleep. Moreover, when CO2 is added to the inspired air, glottic aperture increased in five of nine trials without changes in sleep stage. We also observed a significant negative correlation between glottic width and the VED, independent of the CO2 level. We conclude that during nIPPV glottis narrowing results in a decrease in the proportion of the delivered tidal volume reaching the lungs