Improvements of functional electrical stimulations parameter

Forbedring af funktionel elektrisk stimulerings parametre

Ganeswarathas, Sahana ; Lykholt, Line Elisabeth

4. term

Biomedical Engineering and Informatics, Master

2014

2014-08-14

128

Denne afhandling undersøger to spørgsmål inden for elektrisk stimulation af nerver og muskler. For det første: hvordan formen på elektriske pulser påvirker, hvilke dele af en nerve der aktiveres (rekrutteringsselektivitet), når man bruger en ny kombineret interfascikulær og manchet-elektrode (CICE) i et laboratorieforsøg på isolerede grisenerver. For det andet: om information fra intramuskulær EMG (iEMG) kan bruges til pålideligt at beskrive bevægelse og udviklingen af muskeltræthed i en rottemodel. I nerveforsøget blev CICE placeret både rundt om og inde i nerven for at øge selektiviteten under funktionel elektrisk stimulation. Vi undersøgte fem forskellige pulsformer og deres kombination. Resultaterne viste, at en kombination af de fem pulsformer øgede selektiviteten, at CICE gav højere selektivitet end en almindelig manchet-elektrode alene, og at den fjerde pulsform gav den mest selektive aktivering af fascikler (nervebundter). I det andet forsøg blev en rotte stimuleret med langsforløbende interfascikulære elektroder i bagbenet, mens ankelvinkel (et simpelt mål for bevægelse) og iEMG blev målt. Når musklerne blev trætte, faldt både ankelvinkel og iEMG-amplitude. Sammenhængen mellem ankelvinkel og iEMG var stærkere ved stimulationsfrekvenser over 40 Hz. Desuden tydede resultaterne på, at signaler fra én af underbensmusklerne (TA) var mere pålidelige som feedback end en anden (GM), fordi TA viste højere korrelation. Samlet peger resultaterne på, at både pulsform og elektrodedesign er vigtige for at målrette nerveaktivering, og at iEMG kan give nyttig feedback om bevægelse og muskeltræthed.

This thesis addresses two questions in electrical stimulation of nerves and muscles. First, how the shape of electrical pulses affects which parts of a nerve are activated (recruitment selectivity) when using a novel combined interfascicular and cuff electrode (CICE) in a laboratory model with isolated pig nerves. Second, whether information from intramuscular EMG (iEMG) can reliably reflect movement and the development of muscle fatigue in a rat model. In the nerve experiment, the CICE was placed both around and within the nerve to maximize selectivity during functional electrical stimulation. Five different pulse shapes and their combination were tested. The results showed that using a combination of the five pulse shapes increased selectivity, the CICE achieved higher selectivity than a cuff electrode alone, and the fourth pulse shape produced the most selective activation of fascicles (bundles of nerve fibers). In the second experiment, a rat hindlimb was stimulated using longitudinal intrafascicular electrodes while ankle angle (a simple measure of movement) and iEMG were recorded. As the muscles fatigued, both ankle angle and iEMG amplitude decreased. The correlation between ankle angle and iEMG was stronger when stimulation frequencies above 40 Hz were applied. The findings also indicated that one of the lower-leg muscles (TA) may be a more reliable source of feedback than another (GM), because TA showed a higher correlation. Overall, the results suggest that both pulse shape and electrode design matter for selective nerve activation, and that iEMG can provide useful feedback about movement and muscle fatigue.

[This abstract was generated with the help of AI]

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