Search

Nathalie Demaeyer,1 Marie Bruyneel1,2 1Department of Pneumology, CHU Saint-Pierre, Université Libre de Bruxelles, Brussels, Belgium; 2Department of Pneumology, CHU Brugmann, Université Libre de Bruxelles, Brussels, BelgiumCorrespondence: Marie Bruyneel, Department of Pneumology, CHU Saint-Pierre, 322 rue haute, Brussels, 1000, Belgium, Tel +3225354219, Fax +3225353362, Email marie.bruyneel@stpierre-bru.beAbstract: The prevalence of obstructive sleep apnea (OSA) among the bariatric surgery population is estimated to be 45– 70%. However, weight loss obtained by bariatric surgery is not always associated with full remission of OSA, suggesting that other confounding factors are present. This article aims to review the current literature, focusing on factors that could predict the persistence of OSA after bariatric surgery. For this purpose, relevant studies of more than 50 patients that assessed pre- and post-operative presence and severity of OSA detected by poly(somno)graphy (PG/PSG) in bariatric populations were collected. Six retrospective and prospective studies were evaluated that included 1302 OSA patients, with a BMI range of 42.6 to 56 kg/m2, age range of 44.8 to 50.7 years, and percentage of women ranging from 45% to 91%. The studies were very heterogeneous regarding type of bariatric surgery, diagnostic criteria for OSA and OSA remission, and delay of OSA reassessment. OSA remission was observed in 26% to 76% of patients at 11– 12 months post-surgery. Loss to follow-up was high in all studies, leading to a potential underestimation of OSA remission. Based on this limited sample of bariatric patients, age, pre-operative OSA severity, proportion of weight loss, and type 2 diabetes (T2D) were identified as factors associated with OSA persistence but the results were inconsistent between studies regarding the impact of age and the magnitude of weight loss. Several other factors may potentially lead to OSA persistence in the bariatric surgery population, such as fat distribution, ethnicity, anatomical predisposition, pathophysiological traits, supine position, and REM-predominant hypopnea and apnea. Further well-conducted multicentric prospective studies are needed to document the importance of these factors to achieve a better understanding of OSA persistence after bariatric surgery in obese patients.Keywords: bariatric surgery, gastric sleeve, gastric bypass, obstructive sleep apnea, polygraphy, polysomnography

Nathan Blekic,1 Ionela Bold,1 Thomas Mettay,2 Marie Bruyneel1,2 1Department of Pulmonary Medicine, Saint-Pierre University Hospital, Brussels, Belgium and Université Libre de Bruxelles, Brussels, Belgium; 2Department of Pulmonary Medicine, Brugmann University Hospital, Brussels, Belgium and Université Libre de Bruxelles, Brussels, BelgiumCorrespondence: Marie Bruyneel, Department of Pulmonary Medicine, Saint-Pierre University Hospital, Rue Haute, 322, Brussels, 1000, Belgium, Tel +322 5354219, Fax: +322 5353362, Email marie.bruyneel@stpierre-bru.beAbstract: Various phenotypes of obstructive sleep apnea (OSA) have been recently described and are poorly assessed by the commonly used polysomnographic indices, such as the apnea–hypopnea index and oxygen desaturation index. Nocturnal hypoxemia is the hallmark of OSA and new quantitative markers, as hypoxic burden or desaturation severity, have been shown to be associated with cardiovascular (CV) mortality. The purpose of this overview is to review the endophenotypical and clinical characteristics of OSA, the current metrics, and to analyze different measurements of hypoxemia in OSA to predict the cardiovascular impact (eg hypoxic burden). Potential interest of multidimensional models to classify OSA, such as BAVENO classification, is also discussed, with the goal of focusing on specific endophenotypes that are likely to develop CV comorbidities, in order to guide clinicians to more aggressive management of OSA in these individuals.Keywords: obstructive sleep apnea, oxygen desaturation index, hypoxic burden, apnea–hypopnea index, polysomnography, home sleep apnea testing

Marie Bruyneel,1 Thomas Sersté2,3 1Sleep Unit, Department of Pneumology, Centre Hospitalier Universitaire Saint Pierre, Université Libre de Bruxelles, Brussels, Belgium; 2Department of Hepato-gastroenterology, Centre Hospitalier Universitaire Saint Pierre, Université Libre de Bruxelles, Brussels, Belgium; 3Liver Transplantation Unit, Department of Hepato-gastroenterology, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium Abstract: Sleep–wake disturbances are common in liver cirrhosis and associated with impaired quality of life. The most common abnormalities are insomnia (difficulties falling asleep and maintaining sleep, or unrefreshing sleep), excessive daytime sleepiness, and sleep–wake inversion (disturbances of circadian rhythmicity). The underlying pathophysiological mechanisms for sleep disturbances in cirrhosis are complex and may include disturbed metabolism of melatonin and glucose, alterations in thermoregulation, and altered ghrelin secretion profiles. Sleep–wake abnormalities are related to the presence of hepatic encephalopathy (HE) and improvement in sleep parameters can be observed when HE is properly managed. A few non-specific treatments for sleep–wake abnormalities have been tried with encouraging results for hydroxyzine and modafinil. However, due to the potential for medication toxicity in these disabled patients, further studies are needed to address the potential role of non-drug therapies in this population (eg, cognitive behavioral therapy, mindfulness, yoga) that have demonstrated usefulness in insomnia disorders. Keywords: sleep disorders, hepatic encephalopathy, liver cirrhosis, excessive daytime sleepiness, circadian rhythm, insomnia

The paper continues along the work initiated by the authors in taking into account stress constraints in topology optimization of continuum structures. Revisiting some of their last developments in this field, the authors point out the importance of considering stress constraints as soon as the preliminary design phase, that is, to include stress constraints in the topology optimization problem in order to get the most appropriate structural layout. Numerical applications that can be solved using these new developments make possible to exhibit interesting results related to the specific nature of strength based structural layout for maximum strength compared to maximum stiffness. This particular character of stress design is clearly demonstrated in two kinds of situations: once several load cases are considered and when unequal stress limits in tension and compression are involved.

The open hole tension (OHT) test is one of the standard composite material qualification tests at the coupon level. Predicting OHT strengths using finite element models is essential to minimize the number of tests and associated costs. Present article demonstrates the tensile strength prediction of OHT specimens using Ladevèze (LMT-Cachan) mesomodel in conjunction with damage rate bound (DRB) based delay damage. Intra-laminar ply failure and interface failure are taken into account in the current research. These intraply and interface models are coded as user subroutines in LS-Dyna explicit commercial solver. Matrix in-situ strengths are used to account for ply thickness effects in the finite element simulations. Effect of ply, sub-laminate or in-plane scaling effects on OHT strength are investigated. A calibration procedure for the DRB delay damage constants is proposed. The robustness of the DRB delay damage is evaluated in mitigating mesh size effects by considering two types of mesh topologies. All the test data is taken from the scientific literature. Comparison between tests and present finite element predictions is made in terms of failure stress, failure modes and damage sequence events. Predictions from current finite element models matched well in the matrix or delamination failure mode dominated test cases. A reasonably acceptable agreement was observed in test cases with fiber dominant failure. [ABSTRACT FROM AUTHOR]