A wireless, implantable, dual-channel phrenic nerve stimulator for diaphragm pacing using electromagnetic resonance coupling

Implantable diaphragm pacing (DP) system can effectively restore patients’ breathing. Conventional diaphragm pacemakers have some practical limitations, such as transmission stability and high price. This study proposes an innovative, wirelessly powered dual-channel and inexpensive DP system to overcome some of these constraints. The system realizes wireless power supply based on electromagnetic resonance coupling to improve stability. It comprised an external controller, two off-body transmitters and two in-vivo rectifier-integrated receivers. PCB spiral coils are used for energy transmission in wireless systems to ensure system stability and convenient processing. Receiver encapsulated with biocompatible PDMS convert received power into electrical stimulation energy. Stimulation waveform, multi-media environment and animal experimental tests were conducted to validate system’s performance. Specific absorption rate (SAR) in human tissue was calculated to confirm safety of implantation. Electrical stimulation parameters of the proposed DP system can be precisely adjusted. The stimulation amplitude range is 3–12 V with 0.1 V step resolution. Pulse width and frequency are adjustable from 100-300 µs and 10–100 Hz respectively. The breathing cycle and inhalation time can also be set individually. Wireless energy transmission has wide transmission distance (＞14 mm), good anti-offset capability (horizontal offset＞8mm) and implantation safety (SAR＜1.6 W/kg). Further time series of stimulation signals issued by the two channels are synchronized. The developed system effectively realizes respiratory response of animals to bilateral phrenic nerve stimulation with 17 mm wireless energy transmission distance and implantation of two receivers in vivo. Our work provides a new optimization scheme for the design of implantable diaphragm pacemaker.