Integrated Adaptive Closed Loop Electronic Systems for Advanced Obesity Treatment

Abstract

The increase in morbidity due to obesity, coupled with risks, complexity and cost of existing interventions have encouraged researchers to look at alternative obesity treatment techniques. Obesity management can either begin at a stage where, there is no alternative other than surgery to treat the person or at a pre-emptive stage where the onset of morbid obesity can be prevented through intelligent feedback on making lifestyle changes. In this research, an integrated system or technological platform is described, to manage morbid obesity therapeutically through intelligent Vagus Nerve Stimulation (VNS), as a minimally invasive alternative to highly invasive approaches, such as bariatric surgery. An emerging therapeutic neuromodulatory obesity treatment technique is VNS. VNS has shown traction in tackling obesity with minimally invasive surgical impact on the body and no anatomical modi caton to the body. The data from from clinical studies have demonstrated the clinical feasibility of using VNS as an obesity management technique and have also supported commercially available solutions such as the VBLOC Maestro system, a VNS implant for obesity management by ReShape Lifesciences (previously EnteroMedics). However, the current state of the art VNS consists of obesity management technology in which a neural stimulator implant is interfaced to the vagus nerve using non-piercing cu ff electrodes. A key de ficiency in the current technology is the lack of intelligent feedback parameters to impact therapy decisions, in this case when and how much therapeutic stimulation dosage to be delivered. Previous studies have utilised fixed VNS parameters on patients who have Body Mass Index (BMI) within a pre-selected band. The stimulation parameters may di ffer signi ficantly between patients and studies have demonstrated that VNS administered in relation to meal intake on a daily basis, shows double the percentage weight loss observed during chronic VNS. In this research, the use of dual mode biosignal recording has been proposed to enable intelligent closed loop VNS. This thesis describes an integrated platform with neurochemical and electrical sensor interfacing with the vagus nerve, to record and process electrical and chemical signals on the nerve using the same sensor and intelligently stimulate the vagus nerve. The start of stimulation is governed by the presence of a chemical signature speci c to the presence of a gut hormone. The dosage of electrical stimulation is determined on the basis of electrical Compound Nerve Action Potential (CNAP) signals, which can be used to create a fiber profi le of the nerve. As a work in progress, this thesis also presents proof-of-concept results to demonstrate the potential to record and monitor salivary leptin hormone concentration, as a feedback signal to predict weight loss in achieving early stage, preventive management of obesity through food-habit or dietary and lifestyle changes.