FES Principles & Applications Chung-huang Yu Intelligent Mechatronic Assistive Device Lab Department of Physical Therapy and Assistive Technology National Yang Ming University Functional Electrical Stimulation

What is Electrical Stimulation (ES)? Electrical Stimulation cause muscle contraction Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Can we make ES functional? Yes! (theoretically) Why, in theory? In body, very movement is actuated by muscle contraction. Why, in practice? Independence & Quality of Life Maintain muscle volume Improve physiological condition Psychological Benefit Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

The terms Functional Electrical Stimulation (FES) Functional Neuro-Muscular Electrical Stimulation (FNMES) A technique that utilizes patterned electrical stimulation of neural tissue with the purpose of restoring or enhancing a lost or diminished function Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

What have been done?

What muscle type have been targeted? skeletal distal muscles axial muscle (few - diaphragm) smooth bladder bow sexual organ cardiac (pacemaker) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

What have been done on limb muscles? upper-limb hand grasping & release hand orientation (wrist, elbow, shoulder) whole upper-limb(s) -> not yet lower limb ankle (drop-foot - dorsiflexor) knee (standing - quadriceps) whole leg (standing, walking, cycling) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Applications of Electrical Stimulation Vision restoration Epilepsy control Cochlear implant Tremor control Cardiac pacing Phrenic pacing Control of reaching and grasping Bowel emptying Scoliosis control Bladder empting and control of incontinence Muscles exercise Control of standing and walking Wound healing Spasticity reduction Pain suppression Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Some examples

The history of FES before 19th century  Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

First registered FES work Liberson, et al 1961 Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Parastep (Sigmedics Inc.) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Parastep System Components Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Freehand Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Bionic Glove Restoration of hand function in C5-6 tetraplegia and CVA Wrist movement must be preserved 3 channels self-adhesive electrodes over motor points Conductive panels in the glove make contact electrodes Control: wrist movements (tenodesis) sensed by a transducer Wrist flexed > extensors tension > hand opens Wrist extended > flexors tension > hand closes Independent Don-Doff Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Lower Limb: Odstock foot drop stimulator One channel stimulator Stimulation: common peroneal nerve at head of fibula (TA) or popliteal fossa (withdrawal reflex) Heel switch trigger: Heel off > stimulation ON Heel on > stimulation OFF Rise and fall stimulation envelope can be adjusted Odstock 2 Channel Stimulator (O2CHS) for bilateral dropped foot Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Handmaster (NESS, Israel) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

How can we make it functional? The key aspects Understand Human Sensory-Motor System Residual capacities Paralysis Define what “Normal” functions to restore How to meet the gap? Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Human Sensory-Motor System Planning, coordination (Cerebellum & Basal Ganglia) Visual Vestibular Program Movement (Supplemental & Premotor)  Motor Control CNS Muscles Motor Neuron Muscle Fibres Spinal Cord Corticospinal tract Sensory Nerve Sensory Feedback Reach & Fine Movement (Motor Cortex)  Posture & Balance (Braim Stem) Skin: Touch, Pressure, Vibration  Central Pattern Generator Reflex (stretch, withdraw, inverse myotatic)  Golgi: Force Capsule: Extreme Angle Spindle: Length, Velocity Feed forward: 1. Synergistic 2. Antagonist Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

What are “normal” functions? Is it necessary to be “normal”? Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Types of Functions Functional Types Functional Requirements Kinematically open Kinematically closed Functional Requirements State change Sit-to-stand, drop-foot Constant regulation Functional Joint Involved Single Joint v.s. Multiple Joint Single d.o.f. vs. Multiple d.o.f. Single limb v.s. Multiple limbs. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

How can we make ES functional? Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Artificial Parts in an FES system Stimulator Controller Sensors Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Stimulator :The Physiological basics (1)? Why electrical stimulation cause contraction? What relations between muscle contraction and stimulation pattern? What stimulation parameter? Unipolar v.s. Bi-phasic Element waveform? Pulse width, height Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Stimulator: Physiological basics (2)? What stimulation parameter? Single pulse, doublet, triplet, etc. Frequency between elements Fixed v.s. Sweep Overall envelop Muscle Response threshold, saturation, in-between shape short term effect (fatigue) long term effect (muscle transfer, volume, etc. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Problems/Difficulties of Paralyzed Muscle (1) Excitable? Spasiticity What is the response to stimulation? Force Stimulation Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Problems / Difficulties of Paralyzed Muscle (2) Individual motor unit (David Winter, 1990) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Problems / Difficulties of Paralyzed Muscle (3) Muscle Group Selectivity Surface electrode (rough, limited muscle sites, high working power, don-doff, etc.) implant electrode (invasive, large number of electrodes, breakage) recruitment sequence size principle F voluntary >> F implant >> F surface F normal >> F paraplegic Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Problems / Difficulties of Paralyzed Muscle (4) Muscle Group Biarticular Muscle n-n & non-linear mapping between stimulation and response Muscle Itself Fatigue Time-Varying short-term long-term (muscle type change) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

What do we want to control? stationary position withdraw trajectories accelerations joint moment joint stiffness contact forces Contact Slip reactions forces Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Control Strategies Functionally automatically triggered Open Drop-foot (foot switch) Close Cycling (crank angle) Functionally automatically regulated Close CHRELMS Artificially triggered Open Handmaster Close Demark (slip), Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Difficulties in Sensor system Why sensors in a FES system Feedback control Command controller Artificial sensors limited type limited number limited accuracy don-doff Natural sensors (Nerve cuff) Demark & Canada Group Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Three levels of concern Command Source Natural, subconscious Artificial, Volitional Command Type Trigger Regulation Artificial control Open-loop Close-loop (position, trajectory, force, slip, COG, etc.) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Object of an FES system: Real-time and Patient Driven Real-time regulation Sensors position of joint contact forces Automatic Controller what algorithm Patient Driven What capacities to use? Command controller? Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Application of FES systems User capacity and paralysis Target function analysis Stimulation Patterns System Modeling Control Strategies Other considerations Safety, Economy, Cosmetic, Don-doff etc. Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Conclusions FES systems as orthosis based on superficial stimulation still have low acceptance due to practical reasons: long Don-Doff time, electrode positioning, braking parts, high EC/efficiency ratio, complicated to set and adjust -> Implants After periods of FES training patients show carry over effects -> FES devices can be used as therapeutic tool combined with conventional physiotherapy Functional Electrical Therapy (FET) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Design Example: CHRELMS Restoration of standing function to paraplegic by Functional Electrical Stimulation

FES standing/walking FES Normal Oxygen cost (ml/kg/m) 0.6 0.15 Speed (m/min) 60 85 Heart Rate (beats/min) 118 95 Use of upper Extremities 23% 0% Cost (NT$500,000) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Why FES walking at all? Psychological Effect Simple forward progressing only Short distance, i.e. fatigue quickly high energy still wheel chair dependent high cost Cardiovascular bone loading muscle exercise Psychological Effect Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Long term Goals: Good standing Good walking Standing up: at will, trajectory, speed Standing: longer, more comfortable, maneuvers Sitting down: controlled descent Good walking long distance walk walk in community (different surface) different direction, step length, speed Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

But paraplegics do stand ! Supported Standing ¹ Free-hand Standing Example: vertical back standing up Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Kinematics Analysis: controllable ? d.o.f. =3 (not 6) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Kinetic Analysis: Force Balance Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Novel Concept: Deficit as control signals Leg moment produced from Upper-body Upper-body Activities Control Signals (later) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Proposed Control System Deficits as error signals for artificial control Advantages: Patient driven natural error signals for each joint each axis no anthropometric data required less demanding of sensors handle reactions joint positions Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Theoretical Difficulties and Assumptions Leg Joints in alignment -> maneuver Mapping to desired muscle -> brain Bi-articulator muscles Muscle force change with length & velocity Muscle fatigue Static Indeterminacy -> (Discussed Later) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

System Setup Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Software: controller Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Software (LabVIEW) Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

The subject Subject : TC (8 years after accident) Gender: Male, Age: 49 Height: 1.85 m, Weight: 85 kg Lesion: T6 complete FES standing user for 7 years Asymmetry: left thigh is 5 cm shorter Crooked Spine Remarried during our experiment period Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Control Parameters Three channels each leg Static Indeterminacy (i.e. gluteus, quadriceps, calf) Static Indeterminacy Conjugate Matrix Control Parameter Tuning I = 0.3, 1, 3 Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

CHRELMS : Standing Up Consistent timing -> enable to learn “Quick Knee Locking” Able to half-stand Asymmetry Better Control but not smaller force Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Standing maneuver Posture Switching- Prolong Standing Free-one hand Swaying Forward Swaying Backward Swaying Leftward Swaying Rightward Free-one hand Bending the knees Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

CHRELMS : Sitting down “Knee moment reduction” strategy 40.2% Moment due to Body Weight 89.5% Rate of Moment Change “Release & Re-catch” Prefer Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Conclusion for the Controller Deficits provide 3D signals but 2D seems enough No preset mode/function Perform different tasks with the same control parameter Control of speed Feel of lower limbs with ability to correct posture Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

Conclusion of the Study Deficits: better understanding of paraplegic standing Control system simple & effective user preference potentially practical Supported Standing should be considered by overall system level Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

The future of an FES system? Advance of Electronic technique: System-on-Chip Micro Sensors Micro Stimulator Wireless System Collaboration of Multi-disciplines Engineers Clinical members Patients Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.

FES clinic Department of Physical Therapy and Assistive Technology (Institute of Rehabilitation Science & Technology) , National Yang Ming University.