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Background: Gastric electrical stimulation (GES) has been studied for decades as a promising treatment for obesity. Stimulation pulses with fixed amplitude and pulse width are usually applied, but these have limitations with regard to overcoming habituation to GES and inter-subject variation. This study aims to analyze the efficacy of an adaptive GES protocol for reducing food intake and maintaining lean weight in dogs. Methods: Six beagle dogs were implanted with a remotely programmable gastric stimulator. An adaptive protocol was designed to increase the stimulation energy proportionally to the excess of food consumption, with respect to the dogs’ maintenance energy requirements. After surgery and habituation to experimental conditions, the dogs went through both a control and a stimulation period of 4 weeks each, in a randomized order. The stimulation parameters were adapted daily. Body weight, food intake, food intake rate, and postprandial cutaneous electrogastrograms (EGG) were recorded to assess the effect of adaptive GES. Results: Adaptive GES decreased food intake and food intake rate (p < 0.05) resulting in weight maintenance. In the absence of GES, the dogs gained weight (p < 0.05). Postprandial EGG dominant frequency was accelerated by GES (p < 0.05). The strategy of adapting the stimulation energy was effective in causing significant mid-term changes. Conclusion: Adaptive GES is effective for reducing food intake and maintaining lean weight. The proposed adaptive strategy may offer benefits to counter habituation and adapt to inter-subject variation in clinical use of GES for obesity., SCOPUS: ar.j, info:eu-repo/semantics/published

Finite element modelling has been widely used to understand the effect of stimulation on the nerve fibres. Yet the literature on analysis of spontaneous nerve activity is much scarcer. In this study, we introduce a method based on a finite element model, to analyse spontaneous nerve activity with a typical bipolar electrode recording setup, enabling the identification of spontaneously active fibres. We applied our method to the vagus nerve, which plays a key role in refractory epilepsy. We developed a 3D model including dynamic action potential propagation, based on the vagus nerve geometry. The impact of key recording parameters - inter-electrode distance and temperature - and uncontrolled parameters - fibre size and position in the nerve - on the ability to discriminate active fibres were quantified. A specific algorithm was implemented to detect and classify action potentials from recordings and tested on six rats in vivo vagus nerve recordings. Fibre diameters can be discriminated if they are below 3 µm and 7 µm, respectively for inter-electrode distances of 2 mm and 4 mm. The impact of the position of the fibre inside the nerve on fibre diameter discrimination, is limited. The range of active fibres identified by modelling in the vagus nerve of rats is in agreement with ranges found at histology. The nerve fibre diameter, directly proportional to the action potential propagation velocity, is related to a specific physiological function. Estimating the source fibre diameter is thus essential to interpret neural recordings. Among many possible applications, the present method was developed in the context of a project to improve vagus nerve stimulation therapy for epilepsy.

This thesis aims at optimising gastric electrical stimulation (GES) as a therapy against obesity.Obesity has reached pandemic proportions in the 21st century. It is associated with major health issues and has considerable economic and societal costs worldwide. Bariatric surgery is an efficient yet invasive solution, and there are still concerns regarding its procedure-related complication and mortality rates. As an alternative, GES has been investigated in the last few decades with promising pre-clinical results, but further research is needed to overcome current gastrostimulator limits and to offer optimised weight-loss therapy to patients. Therefore, this work presents an implantable device designed to provide a broad range of stimulation patterns, remotely rechargeable and programmable, and implantable by a minimally invasive surgical procedure.To provide minimally invasive surgery, a specific electrode system was characterised and validated in vivo. The device materials and shape were optimised to provide the best anchoring stability while being compatible with the implantation procedure ergonomics. A single port percutaneous procedure was validated on a dog cadaver and in vivo, aiming to secure the electrodes in a single-step release, with dedicated anchoring system and tools. The tools have been designed and manufactured in stainless steel. Compared to widely used multi-port laparoscopy, our single dilated access technique (12 mm of diameter) was proven feasible, safe (no complication in vivo), quick (estimated to 15 minutes for electrode placement), and resulting in a small visible scar (< 5 mm).An implantable gastric stimulator (IGS) has been designed and validated. Its parameter range was selected to optimally impact the gastric motility and promote satiety feeling. The electronic system embeds a bidirectional controllable current source, an inductive power and communication link, and the external systems with graphical interfaces to fully control the stimu, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

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Power efficiency is critical for electrical stimulators. Battery life of wearable stimulators and wireless power transmission in implanted systems are common limiting factors. Boost DC/DC converters are typically needed to increase the supply voltage of the output stage. Traditionally, boost DC/DC converters are used with fast control to regulate the supply voltage of the output. However, since stimulators are acting as current sources, such voltage regulation is not needed. Banking on this, this paper presents a DC/DC conversion strategy aiming to increase power efficiency. It compares, in terms of efficiency, the traditional use of boost converters to two alternatives that could be implemented in future hardware designs., info:eu-repo/semantics/published

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info:eu-repo/semantics/published