Different pulse shapes to obtain small fiber selective activation by anodal blocking--a simulation study.
The aim of this study was to investigate whether it is possible to reduce a charge per pulse, which is needed for selective nerve stimulation. Simulation is performed using a two-part simulation model: a volume conductor model to calculate the electrical potential distribution inside a tripolar cuff electrode and a human fiber model to simulate the fiber response to simulation. Selective stimulation is obtained by anodal block. To obtain anodal block of large fibers, long square pulses (> 350 micros) with a relatively high currents (1-2.5 mA) are usually required. These pulses might not be safe for a long-term application because of a high charge per pulse. In this study, several pulse shapes are proposed that have less charge per pulse compared with the conventional square pulse and would therefore be safer in a chronic application. Compared with the conventional square pulse, it was possible to reduce the charge with all proposed pulse shapes, but the best results are obtained with a combination of a square depolarizing pulse and a blocking pulse. The charge per pulse was up to 32% less with that pulse shape than with a square pulse. Using a hyperpolarizing anodal prepulse preceding a square pulse, it was not possible to block nerve fibers in a whole nerve bundle and to obtain reduction of a charge per phase. Reduction of the charge could be achieved only with spatially selective blocking. The charge per phase was larger for the combination of a hyperpolarizing anodal prepulse and a two-step pulse than for the two-step pulse alone.
Vucković
Aleksandra
A
Center for Sensory Motor Interaction, Aalborg University, DK-9220 Aalborg, Denmark. av@smi.auc.dk
Rijkhoff
Nico J M
NJ
Struijk
Johannes J
JJ
D000200:Action Potentials / Q000502:physiology*; D003198:Computer Simulation; D004558:Electric Stimulation; D004599:Electric Stimulation Therapy / Q000379:methods; D004566:Electrodes; D004567:Electrodes, Implanted; D006801:Humans; D008959:Models, Neurological; D009407:Nerve Block / Q000379:methods*; D009412:Nerve Fibers / Q000502:physiology*; D012445:Sacrococcygeal Region / Q000502:physiology; D013126:Spinal Nerve Roots / Q000502:physiology*