Electrical stimulation of the diaphragm muscle or phrenic nerve, or ventilatory pacing, serves as an alternative to mechanical ventilation. Currently available ventilatory pacing systems are open-loop, requiring long set-up sessions and frequent tuning. A neuromorphic closed-loop bioelectronic controller capable of autonomously adapting current amplitude to achieve a desired breath volume profile has been developed. The controller was able to achieve a desired volume profile in intact animals and restore tidal volume to values observed prior to injury in spinal cord hemisected animals. This controller architecture allows for ventilatory pacing that requires minimal technician input during setup and constantly adapts to account for changes such as those induced by muscle fatigue. The adaptive control system could be used as a respiratory rehabilitation tool to strengthen inspiratory muscles and for automated weaning from mechanical ventilation.
Functional Electrical Stimulation can be used to restore motor functions loss consecutive to spinal cord injury, such as respiratory deficiency due to paralysis of ventilatory muscles. This paper presents a fully configurable IC-centered stimulator designed to investigate muscle stimulation paradigms. It provides 8 current stimulation channels with high-voltage compliance and real-time operation capabilities, to enable a wide range of FES applications. The stimulator can be used in a standalone mode, or within a closed-loop setup. Primary in vivo results show successful drive of respiratory muscles stimulation using a computer-based dedicated controller.
Electrical stimulation of the nervous system is commonly based on biphasic stimulation waveforms, which limits its relevance for some applications, such as selective stimulation. We propose in this paper a stimulator capable of delivering arbitrary waveforms to electrodes, and suitable for non-conventional stimulation strategies. Such a system enables in vivo stimulation protocols with optimized efficacy or energy efficiency. The designed system comprises a High Voltage CMOS ASIC generating a configurable stimulating current, driven by a digital circuitry implemented on a FPGA. After fabrication, the ASIC and system were characterized and tested; they successfully generated programmable waveforms with a frequential content up to 1.2 MHz and a voltage compliance between [−17.9; +18.3] V. The system is not optimum when compared to single application stimulators, but no embedded stimulator in the literature offers an equivalent bandwidth which allows the wide range of stimulation paradigms, including high-frequency blocking stimulation. We consider that this stimulator will help test unconventional stimulation waveforms and can be used to generate proof-of-concept data before designing implantable and application-dedicated implantable stimulators.
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