IEEE transactions on rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society
-
IEEE Trans Rehabil Eng · Sep 2000
Recruitment properties of intramuscular and nerve-trunk stimulating electrodes.
Functionally useful reanimation of paralyzed limbs generally requires reliable, finely graded control of muscle recruitment and force with minimal fatigue. We used force and electromyographic (EMG) recordings in combination with myofibrillar adenosine triphosphatase activity and glycogen depletion analysis to investigate the recruitment properties of intramuscular (IM) and nerve cuff (NC) stimulating electrodes implanted acutely or chronically in cat hindlimbs. Overall, 32 muscles were submaximally stimulated with current intensities producing approximately 20% of maximal twitch force using 330 ms trains of pulses at 20 and 40 pps. ⋯ NC stimulation produced much steeper recruitment curves and a reduced tetanus/twitch ratio compared to IM stimulation. IM stimulation produced more reliable and less fatigable recruitment of a mix of motor unit types that tended to be localized in neuromuscular compartments containing, or adjacent to, the IM electrode. We hypothesize that trains of submaximal stimulation applied through NC electrodes resulted in fluctuating recruitment because this electrode configuration magnifies the effects of refractoriness and small changes in axonal excitability during pulse trains.
-
IEEE Trans Rehabil Eng · Jun 2000
Nerve cuff recordings of muscle afferent activity from tibial and peroneal nerves in rabbit during passive ankle motion.
Activity from muscle afferents regarding ankle kinesthesia was recorded using cuff electrodes in a rabbit preparation in which tactile input from the foot was eliminated. The purpose was to determine if such activity can provide information useful in controlling functional electrical stimulation (FES) systems that restore mobility in spinal injured man. The rabbit's ankle was passively flexed and extended while the activity of the tibial and peroneal nerves was recorded. ⋯ Ankle rotation at higher velocities increased the dynamic stretch evoked responses during the stimulus ramp but showed no effect on the tonic activity during the stimulus plateau. Prestretching the muscles by altering the initial position increased the response to the ramp movement, however, for the peroneal nerve, when the prestretch brought the flexor muscles near to their maximal lengths, the response to additional stretch provided by the ramp movement was diminished. The results indicate that the whole nerve recorded muscle afferent activity may be useful for control of FES assisted standing, because it can indicate the direction of rotation of the passively moved ankle joint, along with coarse information regarding the rate of movement and static joint position.
-
IEEE Trans Rehabil Eng · Mar 2000
Functional electrical stimulation of abdominal muscles to augment tidal volume in spinal cord injury.
Functional electrical stimulation (FES) of abdominal muscles as a method of enhancing ventilation was explored in six neurologically intact subjects and five subjects with spinal cord injury (SCI) who had levels of injury between C4 and C7. Pulmonary ventilation was augmented in both groups predominantly due to an increase in tidal volume. The average increase in tidal volume during FES for the neurologically intact group was 350 ml, while in the SCI group it was 220 ml. ⋯ Therefore, the proposed method might be useful in future clinical practice. The results indicate that FES of abdominal muscles should be more thoroughly explored as a potential technique of ventilatory support in SCI. The results also point to the necessity for further studies of maintaining the condition of the chest wall in the pulmonary rehabilitation of individuals with tetraplegia.
-
IEEE Trans Rehabil Eng · Dec 1998
Neural interfaces for regenerated nerve stimulation and recording.
A class of implantable, regeneration-type neural interfaces (NI's) for mammalian peripheral nerve recording and stimulation were developed using different fabrication processes and integrating purposely designed components. A typical NI comprises three main components: 1) a microfabricated silicon die incorporating a microelectrode array on multiple through-holes, 2) a polymer guidance channel housing the die, and 3) a flexible flat cable connecting the die to an external electronic circuitry. The design and fabrication of the NI's were aimed at achieving long term, reliable implants by taking into careful account the biological, electrical, and mechanical requirements of the specific implant site. ⋯ Morphological and histological evidence showed that nerves regenerated through the NI's and electrophysiological results demonstrated the recovery of electrical functionality. Moreover, the NI's allowed stimulation of the regenerated nerve producing a visible leg/foot contraction. The NI's presented in this paper are being further improved in the authors' laboratories with the ultimate goal of allowing the control of nerve motor and sensory functions in future prosthetic devices.
-
IEEE Trans Rehabil Eng · Sep 1998
Case ReportsTheoretical performance and clinical evaluation of transverse tripolar spinal cord stimulation.
A new type of spinal cord stimulation electrode, providing contact combinations with a transverse orientation, is presented. Electrodes were implanted in the cervical area (C4-C5) of two chronic pain patients and the stimulation results were subsequently simulated with a computer model consisting of a volume conductor model and active nerve fiber models. ⋯ The (a)symmetry of paresthesia could largely be affected in a predictable way by the selection of contact combinations as well. The transverse tripolar combination was shown to give a higher selectivity of paresthesia than monopolar and longitudinal dipolar combinations, at the cost of an increased current (more than twice).