New Dependability Approach for Implanted Medical Devices

International audienceFunctional Electrical Stimulation (FES) is an attractive solution to restore some lost or failing physiological functions. Obviously, the FES system may be hazardous for patient and the reliability and dependability of the system must be maximal. Unfortunately, the present context, where the associated systems are more and more complex and their development needs very cross-disciplinary experts, is not favorable to safety. Moreover, the direct adaptation of the existing dependability techniques from domains such as space or automotive is not suitable. Firstly, this paper proposes a strategy for risk management at system level for FES medical implant. The idea is to give a uniform framework where all possible hazards are highlighted and associated consequences are minimized. Then, the paper focuses on one of the most critical part of the FES system: analog micro-circuit which generates the electrical signal to electrode. As this micro-circuit is the closest to the human tissue, any failure might involve very critical consequences for the patient. We propose a concurrent top-down and bottom-up approach where the critical element

Relationship between ventilator-associated pneumonia and mortality in COVID-19 patients: a planned ancillary analysis of the coVAPid cohort

Background Patients with SARS-CoV-2 infection are at higher risk for ventilator-associated pneumonia (VAP). No study has evaluated the relationship between VAP and mortality in this population, or compared this relationship between SARS-CoV-2 patients and other populations. The main objective of our study was to determine the relationship between VAP and mortality in SARS-CoV-2 patients. Methods Planned ancillary analysis of a multicenter retrospective European cohort. VAP was diagnosed using clinical, radiological and quantitative microbiological criteria. Univariable and multivariable marginal Cox's regression models, with cause-specific hazard for duration of mechanical ventilation and ICU stay, were used to compare outcomes between study groups. Extubation, and ICU discharge alive were considered as events of interest, and mortality as competing event. Findings Of 1576 included patients, 568 were SARS-CoV-2 pneumonia, 482 influenza pneumonia, and 526 no evidence of viral infection at ICU admission. VAP was associated with significantly higher risk for 28-day mortality in SARS-CoV-2 group (adjusted HR 1.65 (95% CI 1.11-2.46), p = 0.013), but not in influenza (1.74 (0.99-3.06), p = 0.052), or no viral infection groups (1.13 (0.68-1.86), p = 0.63). VAP was associated with significantly longer duration of mechanical ventilation in the SARS-CoV-2 group, but not in the influenza or no viral infection groups. VAP was associated with significantly longer duration of ICU stay in the 3 study groups. No significant difference was found in heterogeneity of outcomes related to VAP between the 3 groups, suggesting that the impact of VAP on mortality was not different between study groups. Interpretation VAP was associated with significantly increased 28-day mortality rate in SARS-CoV-2 patients. However, SARS-CoV-2 pneumonia, as compared to influenza pneumonia or no viral infection, did not significantly modify the relationship between VAP and 28-day mortality

a planned ancillary analysis of the coVAPid cohort

Funding: This study was supported in part by a grant from the French government through the «Programme Investissement d’Avenir» (I-SITE ULNE) managed by the Agence Nationale de la Recherche (coVAPid project). The funders of the study had no role in the study design, data collection, analysis, or interpreta tion, writing of the report, or decision to submit for publication.BACKGROUND: Patients with SARS-CoV-2 infection are at higher risk for ventilator-associated pneumonia (VAP). No study has evaluated the relationship between VAP and mortality in this population, or compared this relationship between SARS-CoV-2 patients and other populations. The main objective of our study was to determine the relationship between VAP and mortality in SARS-CoV-2 patients. METHODS: Planned ancillary analysis of a multicenter retrospective European cohort. VAP was diagnosed using clinical, radiological and quantitative microbiological criteria. Univariable and multivariable marginal Cox's regression models, with cause-specific hazard for duration of mechanical ventilation and ICU stay, were used to compare outcomes between study groups. Extubation, and ICU discharge alive were considered as events of interest, and mortality as competing event. FINDINGS: Of 1576 included patients, 568 were SARS-CoV-2 pneumonia, 482 influenza pneumonia, and 526 no evidence of viral infection at ICU admission. VAP was associated with significantly higher risk for 28-day mortality in SARS-CoV-2 (adjusted HR 1.70 (95% CI 1.16-2.47), p = 0.006), and influenza groups (1.75 (1.03-3.02), p = 0.045), but not in the no viral infection group (1.07 (0.64-1.78), p = 0.79). VAP was associated with significantly longer duration of mechanical ventilation in the SARS-CoV-2 group, but not in the influenza or no viral infection groups. VAP was associated with significantly longer duration of ICU stay in the 3 study groups. No significant difference was found in heterogeneity of outcomes related to VAP between the 3 groups, suggesting that the impact of VAP on mortality was not different between study groups. INTERPRETATION: VAP was associated with significantly increased 28-day mortality rate in SARS-CoV-2 patients. However, SARS-CoV-2 pneumonia, as compared to influenza pneumonia or no viral infection, did not significantly modify the relationship between VAP and 28-day mortality. CLINICAL TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov, number NCT04359693.publishersversionpublishe

Sûreté de fonctionnement pour les implants médicaux

Ce papier étudie la sûreté de fonctionnement (SdF) d'un microstimulateur implanté dans le corps humain. Bien qu'il s'agisse d'une application critique, il n'existe pas d'étude standard dans ce domaine contrairement à l'aérospatiale, l'automobile,...Ce papier illustre les caractéristiques générales de la SdF appliqués aux implants médicaux. Ces systèmes délivrent un signal électrique (Stimulation Electrique Fonctionnel) aux nerfs ou aux muscles afin de restaurer des capacités endommagées

Dependability for Implanted Medical Devices

International audienceThis paper presents a study of dependability in the specific case of microstimulator implanted in the human body. In spite of the critical nature of this kind of application, there is no general study or standard of dependability for it. Based on real circuits developed in the DEMAR project, this paper illustrates the general attributes of dependability applied to medical implants. This kind of systems consists in generating an electrical signal (Functional Electrical Stimulation) into a nerve or a muscle to activate it and restore some lost abilities for para or tetraplegia. In this context, this paper highlights some key points of such system to enhance the general dependability

Dependability: A Challenge for Electrical Medical Implant

International audienceFunctional Electrical Stimulation (FES) is an attractive solution to restore some lost or failing physiological functions. Obviously, the FES system may be hazardous for patient and the reliability and dependability of the system must be maximal. Unfortunately, the present context, where the associated systems are more and more complex and their development needs very cross-disciplinary experts, is not favorable to safety. Moreover, the direct adaptation of the existing dependability techniques from domains such as space or automotive is not suitable. Firstly, this paper proposes a strategy for risk management at system level for FES medical implant. The idea is to give a uniform framework where all possible hazards are highlighted and associated consequences are minimized. Then, the paper focuses on critical parts of the FES system: analog micro-circuit which generates the electrical signal to electrode. As this micro-circuit is the closest to the human tissue, any failure might involve very critical consequences for the patient. We propose a concurrent top-down and bottom-up approach where the critical elements are highlighted and an extended risk analysis is performed

Analytical and experimental study of ringing effects in a Fabry–Perot cavity Application to the measurement of high finesses

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Robustness of vectorial laser systems

The polarisation robustness of vectorial lasers with respect to différent kinds of perturbation is theoretically investigated in thé framework of a Landau potential approach. It is shown that usual internat and external perturbations may be classified in two main classes uniform perturbations which alter thé two eigenstates in thé same manner, and differential perturbations that favor one eigenstate with respect to thé other. It is also demonstrated that thé coupling between thé two eigenstates completely modifies thé robustness of thé system to these different types of perturbations. The crucial role of this coupling is experimentally isolated using two original différent arrangements, allowing thé value of thé coupling constant to be tuned around thé value one and then to reach very low coupling values. Good agreement is observed between experiment and theory. In particular, it is shown that systems highly robust with respect to any kind of perturbation can be built in two différent ranges of thé coupling constant, thé first one corresponding to strong coupling regimes and thé second one to very weak coupling régimes.La robustesse en polarisation des lasers vectoriels vis-à-vis de différents types de perturbations est étudiée théoriquement dans le cadre du formalisme du potentiel de Landau. On montre que les perturbations internes et externes usuelles peuvent être classées en deux catégories principales : les perturbations uniformes qui agissent de manière identique sur les deux états propres, et les perturbations différentielles qui favorisent un état propre par rapport à l'autre. On démontre également que la robustesse du système vis-à-vis de ces différentes perturbations dépend fortement de la valeur du couplage entre les deux états propres. Le rôle crucial de ce couplage est mis en évidence expérimentalement grâce à deux montages originaux différents qui permettent de faire varier la constante de couplage autour de la valeur un, puis d'explorer jusqu aux régimes à très faible couplage. Un bon accord est obtenu entre expérience et théorie. En particulier, on prouve qu'un système très robuste à tout type de perturbation peut être réalisé pour deux gammes de couplage très différentes, l'une correspondant à des couplages forts et l'autre à des couplages très faibles

Global Strategy to Guaranty Dependability of Electrical Medical Implanted Devices

International audienceImplanted devices for functional electrical stimulation are successfully used in a growing set of applications. Obviously, it is essential to guarantee the performance, efficiency and reliability of the systems during its entire life inside the human body. The devices have to be biocompatible, with an acceptable level of constraint for the user. Nowadays, advanced implanted devices have reached a high level of complexity, integration and heterogeneity, but reliability of the implants might remain questionable. In this paper, we propose a new dependability-oriented approach of the design of implanted systems. We have established the risk management procedure of the entire system in the form of an algorithm which has to be followed by everyone who participates to the design, the development and the use of the system. The main objective is to give tools and a methodology to maximize the dependability of the system. This algorithm consists of two kinds of concurrent risk analyses. The first risk analysis is dedicated to specific expertise fields or system parts and the second type of analysis use the data from these specific risk analyses to perform a global risk analysis at system level. For each risk analysis, we propose a concurrent top-down/bottom-up approach aiming to detect every critical part and providing guidelines to increase the dependability of both the electrical part of the implant and the whole system. Eventually, our objective is to use this electronic part of the implant as a monitor and a supervisor to increase the global dependability of the implant