Design And Experimental Research Of Implantable Lower Esophageal Sphincter Stimulator Based On Android Bluetooth

Gastro-esophageal reflux disease（GERD）is one of the most common clinical upper gastrointestinal diseases.It occurs when the reflux of gastric contents into the esophagus causes troublesome symptoms and/or complications including heartburn and regurgitation.The global prevalence of GERD is increased across all ages,races and genders,especially in America and Europe.The underlying reflux mechanism of GERD is related to a disorder of the lower esophageal sphincter（LES）.The pathogenesis of GERD includes weakened anti-reflux barriers,delayed gastric emptying,weakened esophageal clearance,weakened esophageal mucosal defenses,and the attack of reflux.Treatment methods of GERD include lifestyle modifications,drug,anti-reflux surgery and engineering methods.The treatment cycle of lifestyle modifications is long and the effect is slow.The drug therapy is a temporary palliative and the symptoms is prone to relapse after stopping the drug,and surgery may cause complications.Therefore,more and more attention has been paid to engineering method,known the functional electrical stimulation（FES）.The advantages of FES include less surgical trauma,quick response,no postoperative complications and side effects,solving patients’dependence on drugs and being controllable.The potential for the treatment of GERD through interventional implantable FES technology is huge,and the clinical needs of patients are also very urgent.So far,Endostim system（in Netherlands）is the only FES device for the treatment of GERD,which has been applied to the clinical trials,but not released on market yet.And only a few research institutes in China have carried out relevant experimental research on LES-FES for the treatment of GERD.In this paper,we propose an intelligent LES stimulator,with Bluetooth communication function based on the previous research of the research group and finally achieve the purpose of treating refractory GERD.The research content of this paper mainly includes:1)Design of the LES-FES system based on Android Bluetooth:The proposed system consists of three modules:an external controller,an Android application（APP）via a smart phone,and an implantable electronic device（IED）.IED includes a bipolar stimulating lead,a bipolar head connector and a receiving module.2)Design of the external controller:The external controller includes a microcontroller（MCU）ARM^?Cortex^?-M3（STM32F103ZET6,ST Inc.）,a UART-Bluetooth module（HC-05,Huicheng Information Technology Inc.）,a power management circuit,a USB interface circuit（virtual serial port）and a rechargeable lithium polymer battery.It receives the parameter setting sent by the Android APP via a Bluetooth module,and then is programmed to generate specific electrical stimulation pulses to the LES.It also provides an adjustable DC power supply voltage to the transmitting circuit.3)Design of the Android APP:The overall task of Android APP development is presented,including the APP’s function,design flow chart,and key technologies.The Android application program is developed to specifically implement the remote control of the external controller and the management of the treatment data from patients.4)Design of an implantable bipolar stimulation lead and biocompatiblepackaging of the IED:The implantable lead is constructed of biocompatible materials,including 2 platinum-iridium stitch electrodes,parylene coating and an outer silicone rubber sheathing with two“butterfly”securing rings.3D models of the packaging molds are designed and the receiving module is packaged with the polydimethylsiloxane（PDMS）.The waterproof performance experiments are also carried out.5)Experimental Research:The characteristics of electric signal were test before and after packaging,with the evaluation of wireless transmission function.Then the position mismatch experiments under three kinds of mediums were designed to get the position tolerance index of the LES-FES system.On this basis,with rabbits as experimental subjects,anal sphincter FES experiments and one-month implantation of LES-FES experiments were carried out respectively.The results show that the treatment by using the LES-FES system based on Android Bluetooth can be realized in the long-term implantation experiment of rabbits,which can not only enhance the pressure of the LES,but also meet the requirements of biocompatibility.