Muscles neural ans electrical Stimulation Pulse amplitude Pulse width MuscleNerve Skeletal Muscle fibers: Type I : red, slow, aerobic Type II : white, fast, anaerobic Alpha motor neurons: small alpha motor neurons : innervate slow muscle fibers large alpha motor neurons : innervate fast muscle fibers
Muscles neural ans electrical Stimulation Muscle contraction mechanisms: recruitment : activation of an increasing number of motor units within a muscle on contraction temporal summation : increasing firing rate of active motor units During voluntary activation, recruitment and temporal summation are two mechanisms that regulate the strenght of muscle contraction, and usually these mechanisms act simultaneously
Types of Electrodes Polarizable electrodes: Ag Nonpolarizable electrodes: Ag_ AgCl
Electrode- Tissue Behavior
Electrode Operating Characteristics
Current wave forms
Electrode Material In choosing the material for an electrode the following factors are of importance: (1) Passive compatibility of the material with tissue (2) Extent of reversible behavior (3) Mechanical compatibility with the tissue
Surface Electrode The main goal of multilayer construction of the self_adhesive electrode is to provide a balanced most equally distributed stimulation current density over the whole electrode to prevent the skin from burns.
Nerve Cuff Electrodes This automatic spiraling electrode is designed to form to the natural shape of the nerve. The cuff electrode has four contracts that can be grouped together to create a stimulation that will activate groups of muscles.
Epimysial Electrodes This electrode has a tandem conductor close coiled lead wire from the connector, covered with a silicone tube (“closed helix”). The epimysial electrode terminates in a Pt-10 Ir disk mounted in a silicone backing reinforced with dacron.
Percutaneous Intramuscular Electrodes The intramuscular electrode has a stainless steel stimulating area wound around the distal end of the lead.
Recruitment : Surface Electrode
Electric Field Between a Positive and Negative Electode
Nerve Excitation Model of myelinated fiber
Secondary Pulse Considerations
Excitation of Myelinated Nerve myelinated nerve fiber to a point source stimulation
Excitation of Myelinated Nerve
Examples of: Commercial FES Systems
HandMaster Nathan Israel 1990 Electrodes: Surface (5) Commands: External Lateral & Palmar Grasp NESS Ltd. Available commercially
Bionic Glove (1996) Prochazka Univ. of Alberta Canada 1996 tenodesis Bionic Glove is OFF Bionic Glove is ON
FreeHand (?) Kilgore KL, Pekham PH Case Western Reserve University OH, USA 1998 Electrodes: (?) Epimysial Sensors: (?) Latera & Palmar Grasp NeuroControl Corp.
FreeHand (1999) Case Western Reserve University
FreeHand (2000) Case Western Reserve University
BION (USC-2000) G. Loeb Univ. Of Southern California 2000 Electrodes : Intramuscular Weight: 0.75 grams Dimentions: 3 mm x 28 mm Advanced Bionic Corporation (for investigation use only)