Biomechanical response of varicose veins to elastic compression: A numerical study.

International audienceA patient-specific finite-element (FE) model of the human leg is developed to model the stress distribution in and around a vein wall in order to determine the biomechanical response of varicose veins to compression treatment. The aim is to investigate the relationship between the local pressure on the soft tissues induced by wearing the compression garment and the development and evolution of varicose veins and various skin-related diseases such as varicose veins and ulcers. Because experimental data on the mechanical properties of healthy superficial veins and varicose veins are scarce in literature, ultrasound images of in vivo varicose veins are acquired and analysed to extract the material constants using Finite Element Model Updating. The decrease in trans-mural pressure, which conditions the effectiveness of compressive treatments, is computed from the simulation results. This constitutes the original added value of the developed model as decrease in trans-mural pressures cannot be assessed experimentally by any other means. Results show that external compression is effective in decreasing the trans-mural pressure, thereby having a positive effect in the control and treatment of vein-related diseases

Murine hematopoietic stem cell activity is derived from pre-circulation embryos but not yolk sacs.

The embryonic site of definitive hematopoietic stem cell (dHSC) origination has been debated for decades. Although an intra-embryonic origin is well supported, the yolk sac (YS) contribution to adult hematopoiesis remains controversial. The same developmental origin makes it difficult to identify specific markers that discern between an intraembryonic versus YS-origin using a lineage trace approach. Additionally, the highly migratory nature of blood cells and the inability of pre-circulatory embryonic cells (i.e., 5-7 somite pairs (sp)) to robustly engraft in transplantation, even after culture, has precluded scientists from properly answering these questions. Here we report robust, multi-lineage and serially transplantable dHSC activity from cultured 2-7sp murine embryonic explants (Em-Ex). dHSC are undetectable in 2-7sp YS explants. Additionally, the engraftment from Em-Ex is confined to an emerging CD31+CD45+c-Kit+CD41- population. In sum, our work supports a model in which the embryo, not the YS, is the major source of lifelong definitive hematopoiesis

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Contribution to characterizing and modeling the medical compression stocking

Ce travail concerne les bas médicaux de compression (BMC). Ce sont des dispositifs médicaux de classe 1 de la Directive Européenne 93-42. Sous forme d’articles chaussants élastiques (chaussette, bas et collant), ils ont pour fonction d’exercer une pression d’interface sur les membres en vue d’apporter un effet thérapeutique dans le cadre des protocoles de soin des maladies veineuses et des troubles lymphatiques. L’objectif de cette thèse est de constituer un ensemble de méthodologies pour caractériser les diverses fonctionnalités des BMC répondant d’une part aux exigences médicales et d’autre part aux attentes implicites des patient(e)s sur l’ensemble de ses caractéristiques essentielles. Le document est structuré en 4 chapitres. Le premier chapitre positionne le rôle des BMC dans le traitement de la maladie veineuse et des troubles lymphatiques. Après une introduction aux structures textiles, le deuxième chapitre est consacré aux techniques d’Identification de la loi de comportement des matériaux (fils et tricots) des BMC. De la connaissance de ces propriétés mécaniques, on en établit les méthodes de calcul permettant de déterminer la pression (paramètre explicite du produit) qu’exerce le BMC sur la jambe. On présente la pression statique et la pression dynamique des BMC. Le troisième chapitre quantifie l’interface sensorielle patient/produit dans le domaine du toucher, du confort thermique et des aspects visuels ; ces paramètres constituent les critères implicites du produit. Enfin, dans une démarche de prise en compte des patient(e)s au coeur du processus thérapeutique, on fait appel aux concepts de la Logique Floue pour appréhender la perception du BMC par les patient(e)s. Cette approche globale de caractérisation des impératifs explicites et des attentes implicites contribue pour une meilleure observance, et par conséquent une efficacité thérapeutique optimisée.This work is related to the medical compression stocking (MCS). These products belong to the medical devices class 1 (EU Directive 93-42). As leg wear (below knee stocking, thigh and panty), their purpose is to exert interface pressure on limbs aiming to provide a therapeutic effect within the treatment programs for venous diseases and lymphatic disorders. The objective of this thesis is to build a set of methods to characterize the various functionalities of MCS corresponding, on the one hand, to the formal medical requirements and, on the other hand, to the patient’s personal expectations. The document is divided into 4 chapters. The first chapter highlights the role of MCS in treatment protocols for venous diseases and lymphatic disorders. A short introduction to textile materials begins the second chapter which is dedicated to the techniques of constitutive law Identification. From the constitutive law (of MCS materials as yarns and knitted fabric), it is then possible to build calculation procedures which allow us to determine the pressure (medical requirements) exerted by MCS on the legs. The notion of static and dynamic pressure is presented. The goal of the third chapter is to quantify the patient/product sensory interface in the field of touch, thermal comfort and visual aspects. These parameters are related to the patient’s expectations. Last but not least, when considering the patient as a major component of the treatment program, some concepts of Fuzzy Logic are involved to study the MCS perception of the patients. This global approach, aiming to characterize formal medical requirements and patient’s personal needs, contributes to improve the treatment compliance, and subsequently to optimize the treatmen

Contribution à la caractérisation et à la modélisation des Bas Médicaux de Compression

Ce travail concerne les bas médicaux de compression (BMC). Ce sont des dispositifs médicaux de classe 1 de la Directive Européenne 93-42. Sous forme d articles chaussants élastiques (chaussette, bas et collant), ils ont pour fonction d exercer une pression d interface sur les membres en vue d apporter un effet thérapeutique dans le cadre des protocoles de soin des maladies veineuses et des troubles lymphatiques. L objectif de cette thèse est de constituer un ensemble de méthodologies pour caractériser les diverses fonctionnalités des BMC répondant d une part aux exigences médicales et d autre part aux attentes implicites des patient(e)s sur l ensemble de ses caractéristiques essentielles. Le document est structuré en 4 chapitres. Le premier chapitre positionne le rôle des BMC dans le traitement de la maladie veineuse et des troubles lymphatiques. Après une introduction aux structures textiles, le deuxième chapitre est consacré aux techniques d Identification de la loi de comportement des matériaux (fils et tricots) des BMC. De la connaissance de ces propriétés mécaniques, on en établit les méthodes de calcul permettant de déterminer la pression (paramètre explicite du produit) qu exerce le BMC sur la jambe. On présente la pression statique et la pression dynamique des BMC. Le troisième chapitre quantifie l interface sensorielle patient/produit dans le domaine du toucher, du confort thermique et des aspects visuels ; ces paramètres constituent les critères implicites du produit. Enfin, dans une démarche de prise en compte des patient(e)s au coeur du processus thérapeutique, on fait appel aux concepts de la Logique Floue pour appréhender la perception du BMC par les patient(e)s. Cette approche globale de caractérisation des impératifs explicites et des attentes implicites contribue pour une meilleure observance, et par conséquent une efficacité thérapeutique optimisée.This work is related to the medical compression stocking (MCS). These products belong to the medical devices class 1 (EU Directive 93-42). As leg wear (below knee stocking, thigh and panty), their purpose is to exert interface pressure on limbs aiming to provide a therapeutic effect within the treatment programs for venous diseases and lymphatic disorders. The objective of this thesis is to build a set of methods to characterize the various functionalities of MCS corresponding, on the one hand, to the formal medical requirements and, on the other hand, to the patient s personal expectations. The document is divided into 4 chapters. The first chapter highlights the role of MCS in treatment protocols for venous diseases and lymphatic disorders. A short introduction to textile materials begins the second chapter which is dedicated to the techniques of constitutive law Identification. From the constitutive law (of MCS materials as yarns and knitted fabric), it is then possible to build calculation procedures which allow us to determine the pressure (medical requirements) exerted by MCS on the legs. The notion of static and dynamic pressure is presented. The goal of the third chapter is to quantify the patient/product sensory interface in the field of touch, thermal comfort and visual aspects. These parameters are related to the patient s expectations. Last but not least, when considering the patient as a major component of the treatment program, some concepts of Fuzzy Logic are involved to study the MCS perception of the patients. This global approach, aiming to characterize formal medical requirements and patient s personal needs, contributes to improve the treatment compliance, and subsequently to optimize the treatmentLILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Experimental assessment and analytical 2D predictions of the stocking pressures induced on a model leg by Medical Compressive Stockings

International audienceStocking supports have represented, for more than two millennia, the most efficient way to treat the veinous diseases and lymphatic disorders. Although this treatment consists solely in the application of a mechanical pressure to help the blood in reaching back the heart, very little is known on this mechanical effort exerted on a human limb by knitted fabrics. However, nowadays the precise assessment of this pressure distribution is crucial in fitting the treatment to the patient pathology and morphology. In order to describe rationally, for the first time, the pressure distribution induced on a leg, a combined experiment-simulation 2D methodology has been set to validate this mechanical approach. The present article is the first part of a two-papers communication. Experimental aspects are presented here, first to measure these stocking pressures on a rigid leg using the SIGaT® device based on a pneumatic sensor. Then, the knitted fabric mechanical response is characterized under uniaxial tension for large strains, to evaluate the simplified Laplace-based pressure that can be compared with the pressure measurements, knowing the local curvature radii of a leg section. This experimental approach is to be completed with numerical simulations of the stocking mechanism on the same model leg

Comparison of low-strength compression stockings with bandages for the treatment of recalcitrant venous ulcers

OBJECTIVE: To compare the proportion and rate of healing, pain, and quality of life of low-strength medical compression stockings (MCS) with traditional bandages applied for the treatment of recalcitrant venous leg ulcers. METHODS: A single-center, randomized, open-label study was performed with consecutive patients. Sigvaris prototype MCS providing 15 mm Hg-25 mm Hg at the ankle were compared with multi-layer short-stretch bandages. In both groups, pads were placed above incompetent perforating veins in the ulcer area. The initial static pressure between the dressing-covered ulcer and the pad was 29 mm Hg and 49 mm Hg with MCS and bandages, respectively. Dynamic pressure measurements showed no difference. Compression was maintained day and night and changed every week. The primary endpoint was healing within 90 days. Secondary endpoints were healing within 180 days, time to healing, pain (weekly Likert scales), and monthly quality of life (ChronIc Venous Insufficiency Quality of Life [CIVIQ] questionnaire). RESULTS: Of 74 patients screened, 60 fulfilled the selection criteria and 55 completed the study; 28 in the MCS and 27 in the bandage group. Ulcers were recurrent (48%), long lasting (mean, 27 months), and large (mean, 13 cm2). All but one patient had deep venous reflux and/or incompetent perforating veins in addition to trunk varices. Characteristics of patients and ulcers were evenly distributed (exception: more edema in the MCS group; P = .019). Healing within 90 days was observed in 36% with MCS and in 48% with bandages (P = .350). Healing within 180 days was documented in 50% with MCS and in 67% with bandages (P = .210). Time to healing was identical. Pain scored 44 and 46 initially (on a scale in which 100 referred to maximum and 0 to no pain) and decreased within the first week to 20 and 28 in the MCS and bandage groups, respectively (P < .001 vs .010). Quality of life showed no difference between the treatment groups. In both groups, pain at 90 days had decreased by half, independent of completion of healing. Physical, social, and psychic impairment improved significantly in patients with healed ulcers only. CONCLUSION: Our study illustrates the difficulty of bringing large and long-standing venous ulcers to heal. The effect of compression with MCS was not different from that of compression with bandages. Both treatments alleviated pain promptly. Quality of life was improved only in patients whose ulcers had healed