Gastric electrical stimulator designed to be implanted by endoscopy
Obesity has reached epidemic proportions, with at least 2.6 million people dying each year because they are overweight or obese. Today, one billion adults are overweight (BMI above 25) and more than 300 million are obese (BMI above 30). In almost half of OECD countries, 1 person in 2 is now overweight or obese. The animated map (top right) illustrates the trend by showing the rate of obese (BMI over 30) in the U.S. over the years. If the recent trends continue, projections suggest that more than 2 persons in 3 will be overweight or obese in some OECD countries within the next 10 years.
Gastric electrostimulation is a technique used to fight obesity. Gastrointestinal stimulator implants have recently shown positive results in helping obese patients to achieve better nutrition and are being clinically tested. Current implants consist of an implanted housing composed of a receiver (or a battery providing the power) and of a stimulator. The housing is placed in a subcutaneous pocket, hence the patient needs to undergo a surgical procedure (such as laparoscopy), which is expensive, requires a long recovery time and presents risks for the patient. In particular, to place the electrodes in the stomach wall, the surgeon needs to go through a thick layer of fat, which increases the risks of complications.
This project aims to design an electrostimulator implanted by endoscopy, which would avoid such a surgical procedure. Main challenges include:
- First, due to the passage through the oesophagus, the device cannot exceed a diameter of 18mm and a volume of 5 cm3. Hence the large cases used for the current implants are inappropriate.
- Second, the device needs to be properly anchored in the stomach to avoid migration or detachment. This requirement is particularly delicate because the layer of the stomach used to attach the implant may be thin and because the implant has to withstand the stomach contractions.
- Third, the device must resist highly acidic environment (the pH in the stomach can be as low as 1), which imposes considerable limitations on the packaging.
- Fourth, the device needs to be easily placed using endoscopic tools. For instance, the electrode should be embedded in the implant and provide in situ connections and sutures are difficult to perform by endoscopy.
- Fifth, the power supply should neither be cumbersome nor require too regular endoscopies to recharge the batteries.
Another part of this project concerns the simulation of the natural electrical activity of the stomach and of the implant stimulation. Its aims is to help understanding the underlying phenomena that induce a feeling of satiety in the patient and, based on this, to deduce optimal stimulation settings.