Computational Tools for the Reliability Assessment and the Engineering Design of Procedures and Devices in Bariatric Surgery.

Obesity is one of the main health concerns worldwide. Bariatric Surgery (BS) is the gold standard treatment for severe obesity. Nevertheless, unsatisfactory weight loss and complications can occur. The efficacy of BS is mainly defined on experiential bases; therefore, a more rational approach is required. The here reported activities aim to show the strength of experimental and computational biomechanics in evaluating stomach functionality depending on bariatric procedure. The experimental activities consisted in insufflation tests on samples of swine stomach to assess the pressure-volume behaviour both in pre- and post-surgical configurations. The investigation pertained to two main bariatric procedures: adjustable gastric banding (AGB) and laparoscopic sleeve gastrectomy (LSG). Subsequently, a computational model of the stomach was exploited to validate and to integrate results from experimental activities, as well as to broad the investigation to a wider scenario of surgical procedures and techniques. Furthermore, the computational approach allowed analysing stress and strain fields within stomach tissues because of food ingestion. Such fields elicit mechanical stimulation of gastric receptors, contributing to release satiety signals. Pressure-volume curves assessed stomach capacity and stiffness according to the surgical procedure. Both AGB and LSG proved to reduce stomach capacity and to increase stiffness, with markedly greater effect for LSG. At an internal pressure of 5 kPa, outcomes showed that in pre-surgical configuration the inflated volume was about 1000 mL, after AGB the inflated volume was slightly lower, while after LSG it fell significantly, reaching 100 mL. Computational modelling techniques showed the influence of bariatric intervention on mechanical stimulation of gastric receptors due to food ingestion. AGB markedly enhanced the mechanical stimulation within the fundus region, while LSG significantly reduced stress and strain intensities. Further computational investigations revealed the potentialities of hybrid endoscopic procedures to induce both reduction of stomach capacity and enhancement of gastric receptors mechanical stimulation. In conclusion, biomechanics proved to be useful for the investigation of BS effects. Future exploitations of the biomechanical methods may largely improve BS reliability, efficacy and penetration rate.

Characterization of the anisotropic mechanical behaviour of colonic tissues: experimental activity and constitutive formulation.

The aim was to investigate the biomechanical behaviour of colonic tissues by a coupled experimental and numerical approach. The wall of the colon is composed of different tissue layers. Within each layer, different fibre families are distributed according to specific spatial orientations, which lead to a strongly anisotropic configuration. Accounting for the complex histology of the tissues, mechanical tests must be planned and designed to evaluate the behaviour of the colonic wall in different directions. Uni-axial tensile tests were performed on tissue specimens from 15 fresh pig colons, accounting for six different loading directions (five specimens for each loading direction). The next step of the investigation was to define an appropriate constitutive framework and develop a procedure for identification of the constitutive parameters. A specific hyperelastic formulation was developed that accounted for the multilayered conformation of the colonic wall and the fibre-reinforced configuration of the tissues. The parameters were identified by inverse analyses of the mechanical tests. The comparison of model results with experimental data, together with the evaluation of satisfaction of material thermomechanics principles, confirmed the reliability of the analysis developed. This work forms the basis for more comprehensive activities that aim to provide computational tools for the interpretation of surgical procedures that involve the gastrointestinal tract, considering the specific biomedical devices adopted.

A bioinspired autonomous swimming robot as a tool for studying goal-directed locomotion.

The bioinspired approach has been key in combining the disciplines of robotics with neuroscience in an effective and promising fashion. Indeed, certain aspects in the field of neuroscience, such as goal-directed locomotion and behaviour selection, can be validated through robotic artefacts. In particular, swimming is a functionally important behaviour where neuromuscular structures, neural control architecture and operation can be replicated artificially following models from biology and neuroscience. In this article, we present a biomimetic system inspired by the lamprey, an early vertebrate that locomotes using anguilliform swimming. The artefact possesses extra- and proprioceptive sensory receptors, muscle-like actuation, distributed embedded control and a vision system. Experiments on optimised swimming and on goal-directed locomotion are reported, as well as the assessment of the performance of the system, which shows high energy efficiency and adaptive behaviour. While the focus is on providing a robotic platform for testing biological models, the reported system can also be of major relevance for the development of engineering system applications.

A novel autonomous, bioinspired swimming robot developed by neuroscientists and bioengineers.

This paper describes the development of a new biorobotic platform inspired by the lamprey. Design, fabrication and implemented control are all based on biomechanical and neuroscientific findings on this eel-like fish. The lamprey model has been extensively studied and characterized in recent years because it possesses all basic functions and control mechanisms of higher vertebrates, while at the same time having fewer neurons and simplified neural structures. The untethered robot has a flexible body driven by compliant actuators with proprioceptive feedback. It also has binocular vision for vision-based navigation. The platform has been successfully and extensively experimentally tested in aquatic environments, has high energy efficiency and is ready to be used as investigation tool for high level motor tasks.

Preliminary results on the design of a tool for inserting of transverse intrafascicular multichannel electrodes (TIME) into the peripheral nervous system.

Transverse intrafascicular multichannel electrodes (TIMEs) are polyimide-based microelectrodes, which are potentially very interesting to restore sensorimotor functions in disabled people. By means of microstimulation of the nerve stump of an amputee, it can be possible to manipulate the phantom limb sensation, to provide sensory feedback to upper limb amputees, and to investigate methods of treatment of phantom limb pain. The current insertion procedure of TIMEs is completely done by hand. This makes the task difficult. This paper presents the preliminary results related to the development of a robotic tool to increase the accuracy in electrode placement and reduced size of the working area. The possibility to manage insertion parameters such as force, velocity, and positioning, could decrease the risk of damaging the nervous tissue, improving the coordination, and making placements repeatable. With the aim of solving the issues avbove, we developed a first prototype of a 4DoF multi-axis device. Additional strategies concerning system components and control are discussed. We performed characterization of implantation mechanics to derive mechanical design specifications for the robotic device. Force caracterization of the pig peripheral nerve during penetration of the needle at three velocities (1, 30, 40mm/sec) was executed. Results shown inverse relationship between maximal force and velocities values. The force values extracted varied between 0.081-0.174 N.

Locomotion of a legged capsule in the gastrointestinal tract: theoretical study and preliminary technological results.

This work illustrates the analysis of locomotion in the gastrointestinal tract obtainable by a legged capsule for diagnostic and therapeutic purposes. A preliminary simulation of the legged locomotion onto slippery and deformable substrates has been performed and -simultaneously- mechanisms for on board actuation of the legs have been developed and tested. Moreover, an engineering translation of medical needs in endoscopy is presented, with some ad hoc solutions for improving diagnostic capabilities.

Grasping and dissecting instrument for hand-assisted laparoscopic surgery: development and early clinical experience.

BACKGROUND: The operative potential of hand-assisted laparoscopic surgery (HALS) could be enhanced by the introduction of a new generation of assisting instruments. These tools will have to meet specific requirements of shape, function, and safety of use. METHODS: Problems related to the working environment of HALS and deriving projectual restrictions of HALS instruments were analyzed in order to develop and manufacture a working prototype with grasping and dissecting properties to assist during HALS procedures. The resulting instrument was mechanically and clinically tested in 22 HALS procedures. RESULTS: The additional benefit of the new device was particularly appreciated during dissection and isolation of vascular pedicles (nephrectomies and splenectomies). It was shown to be safe and effective in providing the additional assistance it was designed for. CONCLUSION: The described grasping and dissecting instrument for HALS is of great value in assisting the surgeon during fine dissection, as required in selected procedures. New generation of HALS instruments should comply with the functional and safety issues analyzed in this report.

Effects of chronic administration of ephedrine during very-low-calorie diets on energy expenditure, protein metabolism and hormone levels in obese subjects.

1. We investigated the effects of the chronic administration of a sympathomimetic agent on energy expenditure, protein metabolism and levels of thyroid hormones and catecholamines in 10 obese subjects after a 6-week very-low-calorie-diet programme (1965 kJ, 60 g of protein, 45 g of carbohydrates). L-(-)-Ephedrine hydrochloride (50 mg three times a day by mouth) or placebo were administered during 2-week periods (weeks 2-5 of the VLCD programme) in a randomized, double-blind, cross-over design. Five subjects began with ephedrine and five with placebo. 2. The results were analysed separately in the two groups. No difference was found between them as regards weight loss during the very-low-calorie diet and drug treatments. Conversely, ephedrine therapy induced a significantly lower daily urinary excretion of nitrogen (and, consequently, a better nitrogen balance) with respect to placebo, independently of the drug sequence. Daily urinary levels of 3-methylhistidine during ephedrine and placebo treatments were similar. The fasting resting metabolic rate (oxygen consumption, ml STP/min) fell significantly during the very-low-calorie diet in both groups, but this effect was partially and significantly prevented by administration of ephedrine. Diet therapy significantly reduced 24 h urine levels of vanillylmandelic acid and homovanillic acid, which, however, increased to pretreatment values during ephedrine treatment. No significant effects were shown on 24 h urinary concentrations of adrenaline, noradrenaline and dopamine during the very-low-calorie diet and/or ephedrine treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Does ephedrine promote weight loss in low-energy-adapted obese women?

A double-blind cross-over randomized study was performed in 10 selected adult overweight and obese (body mass index greater than 27) women who had been adapted to low-energy intake for a long period of time and who had shown difficulty in losing weight with conventional hypocaloric treatment. Combined with diet therapy (1000-1400 kcal/day), l(-)ephedrine hydrochloride (50 mg three times a day per os) or placebo were administered daily before each meal, after a period of stabilization with diet only for 1 month. Each pharmacological treatment lasted for 2 months. Weight loss was significantly (P less than 0.05) greater during the ephedrine period (2.41 +/- 0.61 kg) than during the placebo period (0.64 +/- 0.50 kg). None of the patients presented clinically important side-effects. These preliminary results seem to suggest a possible role for a thermogenic compound such as ephedrine in promoting weight loss in low-energy-adapted obese women.

A controlled trial using ephedrine in the treatment of obesity.

A double-blind controlled study was performed in unselected obese outpatients to assess the effects of ephedrine on weight loss. Patients were treated for 3 months with placebo (group I), 25 mg t.i.d. or 50 mg t.i.d. of ephedrine hydrochloride orally administered (groups II and III, respectively). Dietary treatment consisted of 1000 kcal/day for females and 1200 kcal/day for males. The three groups were matched for age, sex, body mass index and pre-treatment spontaneous caloric intake. Weight loss was similar in all groups. Patients in group III (ephedrine 150 mg/day) showed significantly more side effects than the placebo group. These results do not seem to favour the hypothesis that ephedrine, a thermogenic agent, may be effective in the therapy of unselected simple obesity. On the other hand, it cannot be excluded that the drug may be useful in obese patients in whom defective thermogenesis may be clearly demonstrated.