Functional Neuromuscular Stimulation of the Respiratory Muscles for Patients With Spinal Cord Injury

Respiratory complication is a major cause of morbidity and mortality in patients with spinal cord injury (SCI). These complications arise partly due to the loss of supraspinal control over expiratory and/or inspiratory muscles caused by SCI. Functional neuromuscular stimulation of the respiratory muscles has been used to restore inspiratory and respiratory functions to these patients, helping them to reduce the incidence of respiratory complications and to have more normal lives. This paper covers three types of techniques for respiratory muscle stimulation: functional electric stimulation, functional magnetic stimulation, and semiconductor-based microstimulator stimulation. Functional electrical stimulation has been used to restore breathing to patients with spinal cord injury for several decades. It is a mature and reliable technology, and there are several commercial systems available. Functional magnetic stimulation of the respiratory muscles has been demonstrated to be an effective tool for producing cough in patients with SCI for nearly a decade. This is a safe and noninvasive technology that is well tolerated by most subjects. Semiconductor-based microstimulators have been widely publicized in recent years, and several clinical applications have been demonstrated, including the applications for restoring cough and breathing. This technology may eventually play a major role in respiratory muscle pacing.